Conf08presentation Sm

Linder Technical Conference 20082008

Waveform AnalysisPresented By: Scot MannaPresented By: Scot Manna

MB Automotive Inc

Course Outline

What is waveform analysisWhat is waveform analysis Capturing, Saving, Viewing and Archiving

Waveforms Scots Fave Five Scope & Scan Tool Display Features & p p y

Software Case Studies: The difficult process of what to

look at and what does it mean Building YOUR database, PPT Case Study

D t tiDemonstration

Waveform analysis requires the necessary tools and leads to connect to a vehicle

An understanding of system and circuit g yoperation is necessary for correct interpretation of captured waveformsp p

Scopes and scan tools do not make diagnostic conclusions, You have todiagnostic conclusions, You have to decide what is good or bad

Having known good patterns is very Having known good patterns is very helpful during analysis and building a database should become a priority fordatabase should become a priority for scope users

Analyze

Per the Websters Collegiate Dictionary:Per the Websters Collegiate Dictionary: To study or determine the nature and relationship of the parts by analysisrelationship of the parts by analysis to subject to scientific analysis

Analysis: an examination of a complex, its elements and relationships

Diagnosis

Per Websters Collegiate Dictionary:Per Webster s Collegiate Dictionary: investigation or analysis of the cause or nature of a condition situation or problemnature of a condition, situation or problem a statement or conclusion concerning the

t f h nature or cause of some phenomenon

Repair Path

Problem Vehicle

Symptom: Stalling, Misfire, Etc.

Without Equipment With Equipment

Replace Suspect Part Test Suspect PartAnalyze Resultsy

Can You Fix Cars Without a Scope?

Connections

BackProbe

Inserting a needle style connector into the backside of connectors, one of the most common connections

Pros: Easy to tap into circuits, usually will not negatively impact circuit

Cons: May damage weather seals, sometimes probe may contact wrong circuit, possible i t itt t tiintermittent connection, newer connectors may be difficult to backprobe

Piercing Probes

Probes that use a needle to pierce wire insulation to connect to a circuitP V Pros: Very secure connection, most useful when connectors cannot be probed

Cons: Almost always causes damage tocauses damage to conductor, Tech should seal point of entry through insulation

Non-intrusive Probes

These are probes thatThese are probes that do not require connection into a circuit such as current probes or pressure t dtransducers

Software

Most automotive based scopes today willMost automotive based scopes today will offer optional computer software for viewing and storing captured waveformsviewing and storing captured waveforms

There are aftermarket programs available for waveform storage and annotationfor waveform storage and annotation

These programs can greatly enhance the f ti lit f thfunctionality of the scope

PC-Based scopes by their very design allow these functions seamlessly

Good Habits, Bad Habits

Good Habits Bad HabitsGood Habits Making one more test Saving captured

Bad Habits Be Lazy, pulling the

diagnostic trigger too fastSaving captured waveforms

Annotating captured f

g gg Not testing after repairs Not saving waveforms or

h i d t bwaveforms Keeping equipment and

leads in good shape

having a database Using your scope as a

wheel chockleads in good shape Learning your equipment

and new techniques

wheel chock Not attending training

(who needs more training)

AESWAVE a eform capt re and storage soft areAESWAVE waveform capture and storage software

AES Annowave waveform annotation software

Snap-on ShopStream Connect software

Click Here!

http://www1.snapon.com/diagnostics

You Must Know These Terms

1. Trigger Source 9. Amplitudegg2. Trigger Level3. Trigger Slope

9. Amplitude10. Frequency11 Peak to Peakgg p

4. Trigger Delay5. Trigger Mode

11. Peak to Peak12. Cursors

6. Peak Detect7. Coupling If not then sign up for Guru School!8. Sweep

Guru School!

What to Analyze

Voltage Level Every waveform hasVoltage Level Signal shape Dropouts or Glitches

Every waveform has some of these important Dropouts or Glitches

Amperage Frequency

characteristics. Proper use of a scope

i i Frequency Duty Cycle & Pulse

Width

requires measuring these values as well as knowing what aWidth

Relationships, CKP to CMP and Primary

as knowing what a particular signal is supposed to look like. CMP and Primary

Control, pp

Normal Injector Waveform

I j D iInj Driver Voltage

Drop

Known Good?

The only sure way to know if a displayedThe only sure way to know if a displayed waveform is good or bad is to have a known good waveform from the same typeknown good waveform from the same type of vehicle and the same component using similar test equipment and scalessimilar test equipment and scales

This is what makes waveform analysis so challengingchallenging

1995 Chevy Blazer, 4.3 CFIVery Rough Running

What could be causing the problem with injector firing?What could be causing the problem with injector firing?

Waveform Analysis

Connect Test Save

Annotate Organize Archive

Waveform AnnotationDescribe Vehicle

Describe ConnectionsVehicle Connections

Describe Tests

Organize Files

Annotate Waveforms

Make Case Study

Sample MODIS Waveform

MODIS Waveform Save Data Screen

Dialogue Box for additional information

Sometimes you just dont If it moves I cany jmeasure up!

If it moves, I can see it!

Randy Dillman

Aaron KoeppenIIf I know it, I

can FIX it!Randy Dillman Has anyone seen my trigger?

can FIX it!II Synch I

see it!

Bernie Thompson

John ThorntonMatt Fanslow

Bernie Thompson

My Fave Randy Says: Measure what you test!

Most scopes can make comprehensiveMost scopes can make comprehensive measurements of the signals they display

Linder Tech Guru instructor Randy Dillman yshares one of my favorite case studies illustrating how important it is to know what a i l h ld b d k tsignal should be and make accurate

measurements to determine what may be wrongwrong

Remember: not all failures are pattern failures!

Signal AnalysisCrucial Components - Amplitude

Defined as Vpeak (Vp) for DC signals

Vp or Vpeak-peak (Vpp) for AC signals

Measure from the ground level to peak

Whats really important?

Unique Training Solutions

C St d 1993 W 3 1 iCase Study: 1993 W-car 3.1 vin TT Vehicle is from another shop (a good one)

Engine has a single cylinder miss (seat of the pants)p )

Has new OE ignition wires

Passes flat-rate relative compression test in parking lot


parking lot

Current Ramping MistakesCurrent Ramping Mistakes

Insert pic of wiring

Randy Dillman 2003


Randy Dillman 2003Current Probe set to 100mV = 1ACurrent Probe set to 100mV = 1A

Current Ramping MistakesCurrent Ramping MistakesCursorsCursorsCursorsCursors

Delta Y=465mVDelta Y=465mV

Delta X=4 15msDelta X=4 15msDelta X=4.15msDelta X=4.15ms

Randy Dillman 2003 Randy Dillman 2004

C St d 1993 W 3 1 iCase Study: 1993 W-car 3.1 vin TT

All six injectors fire simultaneously

Current measured in saturation is 465mV=4.65 A

4.65 A / 6 = 775mA each



Delta Y=548 mVDelta Y=548 mV

Randy Dillman 2003After harness repair!After harness repair!

Randy Dillman 2004

Current Ramping MistakesCurrent Ramping Mistakes6 injectors6 injectors

5 injectors5 injectors

Randy Dillman 2003

Delta Y Difference = 920 mVDelta Y Difference = 920 mV

Randy Dillman 2004

C St d 1993 W 3 1 iCase Study: 1993 W-car 3.1 vin TT

Injector harness (cylinder #3) chewed open by rodent Could not be seen before removingby rodent. Could not be seen before removing intake. Only 5 injectors were firingy j g The measured difference was 920mV Use 900mA per injector to make math easier Must be measured in saturation Dont just look for a low impedance fault!


2001 Hyundai Tiburon, Intermittent No-StartCKP Sensor During Cranking, Engine Startsg g, g

Is This CKP Sensor Waveform Good?

How do you know if this is good or bad? A known goodHow do you know if this is good or bad? A known good car to test would be nice!

CKP Sensor at 800 RPM, 2.89 Volts Peak to Peak

New CKP Installed, Engine Cranking, 4.34 Volt P to P

New CKP, Idle, 17.89 Volts Peak to Peak!

Case Study,1989 Olds 98Hard Start

This vehicle is brought in with a hard start gcomplaint when the engine is cold, the engine also runs rough when coldTh PCM i i i d l il k d k The PCM, ignition module, coil pack and crank sensor have been replaced, the problem remainsremains

When attempting a cold start the problem is obvious, seems like a fuel delivery problem

The fuel rail is lifted from the manifold and while cranking the injectors spray erratically, some do not fire at allnot fire at all

1st Test

A synch probe is connected to Cyl #1 andA synch probe is connected to Cyl #1 and a current probe is connected to fuse #7 in the under dash fuse\relay centerthe under dash fuse\relay center

The following scope pattern is observed while crankingwhile cranking

The idea is to see if injector control is lnormal

What is the likely problem?

8X Zoom O t of Stored Wa eform Capt re8X Zoom Out of Stored Waveform CaptureHow Many Injectors Have Fired?

Diagnosis

The current probe shows unusual injectorThe current probe shows unusual injector firing, could the replacement PCM be defective?defective?

What other tests could be done?Th i it h d t 4 t d The scope is switched to 4 trace mode and the two CKP signals are added

Diagnosis

The scope clearly shows an issue with theThe scope clearly shows an issue with the CKP 18X signal

A Delphi CKP sensor is installed and the A Delphi CKP sensor is installed and the car starts and runs fineTh l i t ll d CKP i d f ti ! The newly installed CKP is defective!

Case Study,2001 VW Passat V/6High Load Misfire

This vehicle has a driveability complaintThis vehicle has a driveability complaint along with an illuminated MIL

Codes set are PO300, PO303 and P1395Codes set are PO300, PO303 and P1395 The vehicle misfires under HEAVY load

conditions, near WOT in lower gearsconditions, near WOT in lower gears The 3/5 coil, ignition control module and

PCM have been replacedPCM have been replaced How would you go about diagnosing this

concern?concern?

Note the 17803 (P1395) DTC, Ignition Coil Power Output 3: Electrical Malfunction

Approach

The MODIS will be connected to theThe MODIS will be connected to the vehicle in four channel labscope mode as followsfollows

Channel 1: Coil 1/6 driver signalCh l 2 C il 4/2 d i i l Channel 2: Coil 4/2 driver signal

Channel 3: Coil 3/5 driver signal Channel 4: Low amp current probe to coil

pack voltage feedp g

dCodes are cleared prior to the 2nd road test with the MODIS connected

F.O. = 1-4-3-6-2-5

3-5 coil

4-2 coil

1-6 coil

Analysis The trigger signal for the 3/5 ignition coil is

corruptcorrupt The ignition module and PCM have been

replaced so it is not thought either of these p gcomponents could be causing the problems seen in the signal

The front of the engine lifts noticeably when loaded in the stall

Could this be a factor in the diagnosis? Could there be a resistive short in the trigger

wire?

Diagnosis

A test light (1 8 amp) is connectedA test light (1.8 amp) is connected between battery power and the 3/5 coil trigger lead at the ignition moduletrigger lead at the ignition module

The wiring harness running from the module back to the PCM was moved andmodule back to the PCM was moved and pulled, when the harness was pushed at the back of the engine between the enginethe back of the engine between the engine and firewall the test light would illuminate

B+B+

coil assembly connector disconnected

PCM connector disconnected

harnessdisconnected

Troubling Trans

1995 Jeep Grand CherokeeLimp-in Condition

Diagnosed 11/15/07 at MB Automotive

The Condition

This Jeep is brought in by a transmission shopThis Jeep is brought in by a transmission shop with a complaint of defaulting to limp-in after starting

The transmission solenoids have been replaced An initial scan test reveals 3 codes (21,22 and ( ,

23) for the governor pressure solenoid, the overdrive solenoid and the TCC solenoid

The transmission enters default just after starting

A wiring schematic will be checked to d t i h thi 42RE t tdetermine how this 42RE trans operates electrically

There is a separate TCM that supplies both the power feed and ground for the transmission solenoids

The TCM is located behind the dashboard on the firewall

A scope will be connected to all 3 transA scope will be connected to all 3 trans solenoids and the solenoid feed

Direction

A four channel labscope will be connectedA four channel labscope will be connected to the vehicle, one channel to each solenoid ground, (no particular order) and g ( p )the last channel to the feed circuit with a current probe

The solenoids are tested at start-up by the TCM to determine circuit condition

We need to see what the TCM sees to make a diagnosis

Is this easy work?

NO!

Th l idThe solenoids are tested about .5

seconds after start, this area will be

zoomed in

What Does This Waveform Tell You?

Each of the 3 solenoids is pulsed 3 times b f t i ffbefore turning off

The power is shut down from the TCM because all circuits stay low after cycling (limp-in), the TCM does not keep the solenoids grounded after the self test

The current displayed is very low when the p y ysolenoids are pulsed, can this be right?

A look at the solenoid code charts willA look at the solenoid code charts will answer that question

Diagnosis

The code charts give informationThe code charts give information regarding the solenoids proper resistance

Each of the 3 solenoids have the correct Each of the 3 solenoids have the correct resistanceTh TCM ill b l d The TCM will be replaced

1st Start, New TCM Installed

1994 Olds 88S i O t St llScoping Out Stalls

Diagnosed at MB Automotive11/08/0711/08/07

The Complaint

The customer complains the engine willThe customer complains the engine will stall out when cold but will re-start

Intermittently the engine will stall while Intermittently the engine will stall while idlingTh h b id bl k There has been considerable work performed to correct the problem, plugs,

i i j t d h d k t hwires, injectors and head gaskets have been replaced

1st Impressions

The engine starts and runs OK when firstThe engine starts and runs OK when first checked, the fuel trims were high but a vacuum line was found disconnected

The injectors are checked for proper application, they are rightpp y g

The throttle body is dirty so it is removed and cleaned along with the IAC & MAFg

After several test drives the car runs fine Can it really be this easy?Can it really be this easy?

STALL!

While moving the vehicle on the parking lot, the g p gengine stalls during idle

It seems like a fuel problem, the engine started running rough and stalled it did not cut right offrunning rough and stalled, it did not cut right off like an ignition problem

A 4 channel labscope is connected as follows, Ch 1 t I j #1 Ch 2 t b tChan 1 to Inj #1, Chan 2 current probe to Injector Feed Fuse, Chan 3 current probe to Ignition Module Primary Feed, Chan 4 to Ign M d l T i l D DREFModule Terminal D, DREF

A stall is captured, you make the diagnosis

The Engine Stalls!

Analysis

The PCM cannot control injector firingThe PCM cannot control injector firing properly

This is a sequential fire fuel injection This is a sequential fire fuel injection systemTh DREF i l i h t th PCM t The DREF signal is what the PCM uses to fire injectors and it looks fine

The vehicle needs a PCM With a rebuilt PCM the car runs fine

My Fave Matt, Says:Know Thy Enemy

An understanding of the circuit you areAn understanding of the circuit you are testing as well as the vehicle system you are working on is crucialare working on is crucial

Sometimes you may see a perfect signal but it does not belong on the car you arebut it does not belong on the car you are working on!Th f ll i i i i t h d b The following is a case in point shared by Matt Fanslow from Crag Technologies

1987 Oldsmobile Ninety-Eight

3.8L vin 3

Customer Complaints

Cranks over erratically (similar to timingCranks over erratically (similar to timing being overly advanced)

Engine bucks jerks misfires and stalls Engine bucks, jerks, misfires, and stalls. Intermittently cranks over, but will not start. Gets worse as it warms up.

Relative Compression

Check Out This Starter Current!

Scope some inputs

Relationship to ignition

What could be causing it?

Our engine is firing out of timeOur engine is firing out of time.

D ll i ll th l Dwell is all over the place.

DREF and EST are mirroring CKP

How does this system work and what should the signals look like?should the signals look like?

DESCRIPTIONThe crank sensor is mounted in a pedestal on the front of the engine nearThe crank sensor is mounted in a pedestal on the front of the engine near the harmonic balaner. The sensor is a "hall-effect" switch which depends on a metal interrupter ring, mounted on the balancer to activate it. Windows in the interrupter activate the "hall-effect" switch as they provide a path for the magnetic field between the switch's transducer and it's magnetmagnetic field between the switch s transducer and it s magnet.

OPERATIONWhen the "hall-effect" switch is activated, it grounds the signal line to the C3I module, pulling the crank signal line's applied voltage low which ismodule, pulling the crank signal line s applied voltage low which is interpreted as a crank signal. Because of the way the signal by the crank sensor is created, the signal circuit is always either at a high or low voltage (square wave signal) and three signal pulses are created during each crankshaft revolution. This signal issued by the C3I module to create acrankshaft revolution. This signal issued by the C3I module to create a reference signal which is also a "square wave" signal similar to the crank signal.

The reference signal is used to calculate engine rpm and crankshaft positionThe reference signal is used to calculate engine rpm and crankshaft position by the Electronic Control Module (ECM) . A misadjusted sensor or bent interrupter ring could cause rubbing of the sensor resulting in potential driveability problems such as rough idle, poor performance or a no start condition. Failure to have the correct clearance will damage the sensor.condition. Failure to have the correct clearance will damage the sensor.

The C3I dual crank sensor, secured in an aluminum mounting bracket and bolted to the front left side of the engine timing cover, is partially behind the crankshaft harmonic balancer. A 4-wire harness connector plugs into the sensor and connects it to the module. The dual crank sensor contains two Hall-effect switches with one shared magnet mounted between them. The magnet and each Hall-Effect switch are separated by an air gap. The Hall-Effect switch reacts like a solid-state switch, grounding a low current signal voltage when a magnetic field is present. When the magnetic field is shielded from the switch by a piece of steel placed in the air gap between the switch and the magnet, the signal voltage is not grounded. If the piece of steel is repeatedly moved in and out of the air gap, the signal voltage will appear to cycle. The piece of steel is two concentric interrupt rings mounted to the rear of the crankshaft balancer. Each interrupter ring has blades and windows that, with crankshaft rotation, either block the magnetic field or let it pass to one of the Hall-effect switches. The outer Hall-Effect switch is called the 18X crank sensor because this outer interrupt ring has 18 evenly spaced blades and windows which are all the same width. The 18X crank sensor produces 18 "ON-OFF" pulses per crankshaft revolution. The Hall-effect switch closest to the crankshaft is called the 3X crank sensor because it has 3 different unevenly spaced and different width size windows. The 3X crank sensor produces 3 different length "ON-OFF" pulses per crankshaft revolution. When a 3X interrupter ring is between the magnet and the inner switch, the magnetic field will cause the 3X Hall switch to ground the 3X signal voltage supplied from the C3I module. The 18X interrupt ring and Hall-effect switch react similarly. The C3I module interprets the 18X and 3X pulse signals as an indication of crankshaft position, and must have both signals to fire the correct ignition coil. The C3I module determines crank position for correct ignition coil sequencing by counting how many 18X signal transitions occur during a 3X pulse.

Post repair

My Fave Aaron Says:Make the scope SHOW you the

problemproblem There are many powerful scope usage

techniques, the key to developing a large arsenal of tests is networking with other scope power users

This awesome technique for tracking down q ga misfire like symptom is shared courtesy of Aaron Keoppen from Falls Tire near ppMilwaukee WI

2002 Camry Automatic Transmission 56,000 miles

3.0L 1MZ-FE

Customer Complaint

Customer states, Intermittently Jerky at aboutCustomer states, Intermittently Jerky at about 40 MPH, gets worse as vehicle warms up.

MIL is not Illuminated and No DTCs are stored

Test Drive confirms issue, seat of pants feels like a misfire.e a s e

RepeatableRepeatable

Scan Tool or Scope

Scan ToolScan Tool Mastertech with Toyota Program Card Aftermarket

Scope DSODSO GMM

SCOPE

Primary CurrentPrimary Current

P i V lt Primary Voltage

Secondary Voltage

O2 Sensor Hash

SCOPE

O2 sensor Hash?O2 sensor Hash?

Mi fi i li d h Hi h F Misfiring cylinders show High Frequency oscillations in the O2 sensor wave.

Problem: This vehicle has A\F sensors, ,not conventional Oxygen Sensors

Scan Tool

Toyota data update rate is slowToyota data update rate is slow OE or Aftermarket similar data issues

Toyota misfire counters do not work like a GM or Ford Not live Used for trending/long termg g

The problem was felt during this test drive no misfire counts logged!The problem was felt during this test drive, no misfire counts logged!

What Next?

Scope would not helpScope would not help Scanner no help

Hotline? i-atn?i atn? Call a friend?

Sh t P t ??? Shotgun Parts???

Engine or Transmission?

So far we have no directionSo far we have no direction

W t i it i We can not even answer, is it engine or transmission?

Misfire

Misfire slows down the crankshaftMisfire slows down the crankshaft.

C k h ft t t 720 d 4 Crankshaft rotates 720 degrees per 4-stroke cycle

Is there a signal that we can look at that grepresents crankshaft speed?

Potential Signals

Injector Voltage or CurrentInjector Voltage or Current

Primary currentPrimary current

Trigger Trigger Clean, stable and reliable signal.

Technique

One scope channel on trigger signalCOP i iti d l i d i i l COP ignition module primary drive signal

Test drive

Technique

Steady throttle and load.

TCC should be locked up.

2007 Camry while creating misfire by turning off a Coil

1999 GMC 1500 while turning TCC On and Off

Scanner Waveforms?

Most scan tools today have the ability toMost scan tools today have the ability to display computer data parameters (PIDs) in a graphical format

These displays can often look like waveforms although they are only digital data values

t d hi t hpresented as a histograph These graphs can be displayed live on the

tools display or downloaded to a softwaretools display or downloaded to a software program for graphical display and analysis similar to scope waveform analysisp y

Test drive after new MAF was installed, good fuel enrichment is shown.

Scanner Waveforms

This 2002 Dodge Grand Caravan comes in with gthe complaint of a P0715 code that has not been repaired although several shops have looked at the vanthe van

The trans shop that rebuilt the trans says there is a wiring problemis a wiring problem

The local Chrysler dealer has flashed the PCM and TCM and told the customer there were codes for both transmission sensors but no actual diagnosis, (the customer said they were not very nice)not very nice)

Testing using the KISS Method

A graphing scan tool is connected and theA graphing scan tool is connected and the engine RPM and trans Input speed sensors are graphedsensors are graphed

When slight pressure is exerted on the ISS connector the RPM drops to Zeroconnector the RPM drops to Zero

Can it be this easy?

Testing

The connector is removed and terminalThe connector is removed and terminal drag is checked, it seems fine

The speed sensor is removed and the The speed sensor is removed and the resistance is checked, it is normalA t i l d t th A spare connector is plugged onto the sensor and the resistance is tested while

lli th tpulling on the connector

Repair

A careful inspection of the speed sensorA careful inspection of the speed sensor showed no ID marks other than a Made in India stamp inside the connector cavityp y

The sensor terminal pins sat lower in the body than a new Mopar sensor, and the y pconnector cavity was larger than the OE unit creating a somewhat loose fit

Replacing the sensor and connector repaired the problem

Shaking the ISS Connector After the

Repair!

2000 Chevy Impala3 8 Vi K3.8 Vin K

The engine will start and stall, does not stay running, seems like y g

possible VTD issue

The MAF sensor seems suspectTh MAF i di t d d th The MAF is disconnected and another attempt to start the engine is made

Frame 247 shows the beginning of this attempt

The engine now starts and runs

2003 Monte Carlo, 3.8 Vin K

What is wrong with the following picture?

2001 Cadillac Deville4 6 Vi Y4.6 Vin Y

MIL and stored codes P0171 & P0174, smoke machine test

reveals no leaks.

2002 Chevy Suburban, 8.1 Vin GG

Intermittent Engine StallFuel Pump & Relay Are NewFuel Pump & Relay Are New

Engine at Idle

Stall!

1991 Mercury Tracer1 9 L/4 SOHC1.9 L/4 SOHC

Lean Trim Code

Weak Fuel Pump Bad MAF Restricted Injectors?Weak Fuel Pump, Bad MAF, Restricted Injectors?

The pipe that brings exhaust to the E G R valve was rusted off atThe pipe that brings exhaust to the E.G.R. valve was rusted off at the manifold!

2001 Infiniti G20tSevere Idle Surge and Stall in GearSevere Idle Surge and Stall in Gear

Diagnosed at MB Automotive IncUsing Snap-on VerusUsing Snap on Verus

Problem

This Infiniti has a sudden idle speed dropThis Infiniti has a sudden idle speed drop that at first was intermittent but now seems to be steady and repeatable while running y p gin the bay

If the vehicle is driven, when the idle drop poccurs in gear the engine may stall (customers original complaint)

The Verus is connected and the following scan data is captured

RPM Drop

The RPM graph shows the sudden drop occurring at fairly regular intervals, there is no throttle angle change.

The Idle Control Motor responds to the RPM drop so the PCM is tr ing toThe Idle Control Motor responds to the RPM drop so the PCM is trying to correct the problem, it does not appear to be an IAC issue.

Start of RPM Drop! 800 RPM Current, 30 IAC Steps

RPM falls to 488 IAC has begin to open to pre ent stallRPM falls to 488, IAC has begin to open to prevent stall.

Question?

If the IAC is not closing to cause a drop inIf the IAC is not closing to cause a drop in idle RPM then why is the engine losing speed?speed?

Can other scan data reveal what may be causing the issue?causing the issue?

What else can cause idle RPM changes? Timing, Fuel Delivery or changes in air

quantity!

The Shop Stream software allows the data to be zoomed in on and reviewed. While the Timing is changing it looks to be a result

of the RPM change and not the cause.

The Injector command appears to be the c lprit The injector commandThe Injector command appears to be the culprit. The injector command increases BEFORE the RPM drop occurs. Further data will reveal why!

A\F Alpha is Nissans way of showing Fuel Trim, 100 equals no correction, lower numbers are subtracting fuel and higher numbers are adding fuel. The system isnumbers are subtracting fuel and higher numbers are adding fuel. The system is

subtracting fuel to its idle limit then returning to center. The sudden return to center is a large fuel increase and causes the RPM drop.

Analysis

Fuel trim is a closed loop correction toFuel trim is a closed loop correction to oxygen sensor activity

The goal of the PCM is to cycle the A\F ratio g yrich and lean to create an average ratio at 14.7/1

The PCM makes rich and lean adjustments in response to oxygen sensor activity, if the O2 stays low fuel is added if the O2 stays highstays low fuel is added, if the O2 stays high fuel is subtracted

The O2 sensor SHOULD cycle rich and leanThe O2 sensor SHOULD cycle rich and lean

The o gen sensor is not responding to the A\F Alpha commands TheThe oxygen sensor is not responding to the A\F Alpha commands. The PCM tries to drive the O2 voltage low then gives up and returns trim to

center.

R l ti hi b t RPM A\F Al h I j tRelationship between RPM, A\F Alpha, Injector Pulse Width and Oxygen Sensor Voltage

Testing

The following two Verus screen shots show gthe oxygen sensor being disconnected and reconnected, the O2 voltage drops to zero and returns so we know there is not aand returns so we know there is not a resistive short in the O2 circuit wiring

It must be considered that either the oxygen ygsensor has a problem with its voltage output biased high or there is something making the engine run very richengine run very rich

The O2 sensor is replaced to test the 1sttheory but the problem remains

S D t ith N O SScan Data with New Oxygen Sensor

RPM Graph was Re-scaled

Scan Data After Cleaning MAF Sensor, Note Changing O2 Voltage!

O2 Voltage now responds to A\F Alpha and RPM surge is almost gone!

The Snap-0n Scanner does not show MAF in grams per second when viewing enhanced data

The tool will be switched to Global OBDII to see this critical valueto see this critical value

New MAF Installed! Note Air Flow Rate (g/s)

S D t ith MAF i t ll d!Scan Data with new MAF installed!

The Beginning

A customer drops off a 1997 Cavalier with a 2.2 L/4 with pa hard start complaint and a strange noise from the dashboard

When the key is turned on a noise comes from the dashWhen the key is turned on a noise comes from the dash like a warning buzzer, along with some clicking and blinking cluster lights (very weird)

A scan tool is connected to read codes and the following A scan tool is connected to read codes and the following are present

IPC: B1022, Loss of SIR Serial Data, B1023, Loss of ABS S i l D tABS Serial Data

PCM: P0335, CKP Sensor Ckt. , P0342 CMP Sensor Ckt. Low Voltage and P1629, Anti-Theft Device Signalg g

1st Thoughts

The bizarre behavior makes one believeThe bizarre behavior makes one believe the PCM or Cluster is bad, or both?

The Cluster will loose communication withThe Cluster will loose communication with the scan tool and the PCM is outputting very erratic datay

The engine will not start and there is no spark or injector pulsep j p

What does the following scan tool snap shot point to?p

Snapshot captured KOEO

Test or Replace

The strange PCM behavior suggests theThe strange PCM behavior suggests the box should be replaced

It is easier to pick-up the phone and get aIt is easier to pick up the phone and get a part than to drag out the scope and keep testingg

Proper service procedure dictates checking feeds and grounds BEFORE g greplacing modules, Ken Zanders taught me this, get the scope

Fuel Pump Relay Coil Feed KOEO

Ch 1 = Bat Pos Ch 2 = PCM\IGN Fuse Ch 3 = FP\INJ Fuse

Turning The Key ON

4x Zoom Out!

Diagnosis

There is certainly a power feed problem toThere is certainly a power feed problem to the fuse box as the voltage seen on the scope at the fuse taps confirmscope at the fuse taps confirm

There should be no way for the PCM to cause the erratic voltage supply problemcause the erratic voltage supply problem, the issue must be upstream from the fusesA i iti it h i d d d A new ignition switch is ordered and installed

Does Ign 1 Voltage data support the diagnosis?

My Fave Bernie, Says:

When looking for intermittents it may beWhen looking for intermittents it may be helpful to set the scope to roll mode instead of selecting a triggerinstead of selecting a trigger

When a trigger is set, the scope will only update the display when the triggerupdate the display when the trigger condition is metWh l ki f i t itt t th When looking for intermittents, the more channels the better!

2003 Jeep Liberty3 7 V/6 Intermittent Rough Running or Stall3.7 V/6 Intermittent Rough Running or Stall

This vehicle is experiencing a roughThis vehicle is experiencing a rough running condition during steady cruise periodsperiods

Occasionally the engine can loose power and stalland stall

The 8 channel E-scope is connected to the hi l d t t d ivehicle and test driven

CKP & CMP signals as well as all 6 injectors are connected to the scope

The PCM is double firing a bank of injectors! New PCM fixed the Jeep

1994 Olds 98

Engine Stall or No-Start ProblemDiagnosed at MB AutoDiagnosed at MB Auto

Issue

The vehicle has a stall or intermittent no-The vehicle has a stall or intermittent nostart problem

There has been several attempts to repairThere has been several attempts to repair the problem, new fuel pump & relay, Reman PCM

The problem remains A multi-trace scope will be connected toA multi trace scope will be connected to

try and gain direction or determine the actual fault

Test Strategy

Because it is unknown at the start of a diagnosisBecause it is unknown at the start of a diagnosis where the problem lies it is advantageous to connect to as many circuits as possible to increase the chance of determining the cause should the vehicle act up.

This scope connection can verify ignition primary circuit operation as well as PCM trigger inputs, fuel pump operation and injector voltage supplyfuel pump operation and injector voltage supply and current flow

ATS E-Scope Connection

Chan 1: Current Probe to Injector FuseChan 1: Current Probe to Injector Fuse Chan 2: Current Probe to Fuel Pump Fuse

for Ignition Primary Currentfor Ignition Primary Current Chan 3: Camshaft Sensor Signal Chan 4: CKP 18x Signal Chan 4: CKP 18x Signal Chan 5: CKP 3x Signal

Ch 6 EST (El t i S k Ti i ) Chan 6: EST (Electronic Spark Timing) Chan 7: #1 Fuel Injector Voltage

Injectors

Coils & Fuel Pump

Cam Sensor

CKP 18X

CKP 3X

EST Signal

#1 Injector Voltage

What is Missing?

RememberRemember This?

Analysis

The scope has clearly captured theThe scope has clearly captured the problem, the second trace has no humps visible from the fuel pump all other tracesvisible from the fuel pump, all other traces appear normal

Attention and further analysis will be Attention, and further analysis will be focused on the fuel pump circuitP f d d d ill b t t d f Power feed and ground will be tested for the fuel pump

My Fave John, Says:

Build your database of known goodBuild your database of known good CKP\CMP Synch relationships because these problems can be some of thethese problems can be some of the strangest and most difficult problems to diagnosediagnose.

The following case study illustrates Johns pointpoint.

Case StudyVehicle: 2002 Jeep Grand Cherokee Overland 4.7L vin J 102,000Overland 4.7L vin J 102,000 miles vin: 1J8GW68JX2xxxxxxx

Concern: Shortly after the engine starts, the 30 amp ASD relay fuse blows. The p ytiming chain was just done, and ever sincesince

Performed diagnosis at Hillerichs Car gCare on Friday, February 15, 2008.

Case StudyApproach:Scope ASD fuse circuit current toScope ASD fuse circuit current to observe current activity.Scope the crank and cam sensor signalsScope the crank and cam sensor signals to check for synch.

The 30 amp fuse feeds the ASD relay.y

The relay feeds h PCM O2the PCM, O2

heater relay, hydraulic cooling module,cooling module, the fuel injectors and the coilsand the coils.

The 8 COP coils are fed from the 30 amp fuse via pthe ASD relay.

The crank and cam sensor signals were gaccessed at the PCM (JTEC).PCM (JTEC).

ASD current exceeds 20 amps and blows20 amps and blows the 30 amp fuse

COP primary current exceeds 20 amps and blows the 30 amp fuse

COP primary current: no issue for more than 100 milliseconds

Crank sensor signal

C i lCam sensor signal

Known Good Crank & Cam Si lSignals

This JTEC crank reluctor should have 16This JTEC crank reluctor should have 16 teeth. 4 are wide and 12 are narrow. The sequence is 1 wide and 3 narrow; this repeats 4 times for a total of 16 teeth.p

The cam pulses are 1, 2, 3, 3, 2, 1, 3 and 11.

Coil #1 known good Co #Primary

g

y

Cam SSensor

Crank SSensor

Coil #1 Co #Primaryy

Cam Sknown good Sensorknown good

Crank SSensor

ASD current exceeds 20 amps and blows the 30 amp fuse

the crank and cam are out of synch

COP coil current exceeds 20 amps and blows the 30 amp fuse

Case StudyConcern: Shortly after the engine starts, the 30 amp ASD relay fuse blows. Thethe 30 amp ASD relay fuse blows. The timing chain was just done, and ever sincesince

Diagnosis:gIncorrect cam timing prevent the PCM from properly controlling the COP coilsfrom properly controlling the COP coils dwell. The coils would not turn off which would quickly increase current beyondwould quickly increase current beyond the capability of the 30 amp fuse.

90 crank degrees = 7.61 millisec

the cam error is 2.26 millisec

this edge

h ld bshould be over there

Cam Error

90 crank degrees = 7.61 milliseconds the cam error is 2.26 milliseconds

7.61 msec = 2.26 msec 90 degrees ? degreesg g

? degrees = 26.73 crank degrees

2002 Chevrolet MalibuI t itt t N St t P blIntermittent No-Start Problem

Diagnosed at MB Automotive05/14/0805/14/08

Concern

This Malibu with a 3 1 Vin J engine willThis Malibu with a 3.1 Vin J engine will occasionally crank but not fire

Another shop has checked this issue and Another shop has checked this issue and replaced the ignition module, they feel there is no injector pulse when the no startthere is no injector pulse when the no-start occursA PC b d ill b t d t A PC based scope will be connected to key signals and a scanner is ready to

d d t if th t t hrecord data if the no-start happens

Initial Tests

A current probe connected to the fuseA current probe connected to the fuse feeding the ignition module shows unusual coil dwell control intermittentlycoil dwell control intermittently

There are also some no-start events capturedcaptured

Sometimes while cranking there is a dd b k f th i lik thsudden buck from the engine like the

ignition miss-triggers

Channel A = FP\Inj Fuse Voltage Channel B = FP\Inj Fuse CurrentChannel C = Ign Module Fuse Current Channel D = DREF Signal

Note Erratic Primary Current Dwell Control!

Screen 1 of 5

Channel A DREF Signal Channel B Injector C rrentChannel A = DREF Signal Channel B = Injector CurrentChannel C = Ignition Primary Current Channel D = EST

Screen 2 of 5

Screen 3 of 5

Screen 4 of 5

Screen 5 of 5

After looking at the strange primary current t l it i d id d t l thcontrol it is decided to replace the

aftermarket ignition module with an AC D l itDelco unit

The shop is told it seems like there may be more than one problem but the module certainly does not seem right

After installing the new module no erratic coil firing is seen but after repeated g pattempts the engine cranks and does not start

Running with new module!

DA

C

BB

Normal Engine Start Shown Channel A = DREF Signal Channel B = BatteryNormal Engine Start Shown, Channel A DREF Signal, Channel B Battery Voltage to Ign Module, Channel C= Ign Coil Primary Current, Channel D = EST Signal

When the no-start was captured it is clear to see there is very little applied voltage to thesee there is very little applied voltage to the ignition module

The shop is informed the ignition switch isThe shop is informed the ignition switch is bad

The shop decides to replace the ignition it h th l d i k th hi lswitch themselves and picks up the vehicle

Two weeks later the shop calls back and states the no-start has returned the car isstates the no start has returned, the car is dropped back off

Attempting to start the car reveals the problem is present so the car is pushed in and connected to a scope, injector #6 voltage and current are checkedand current are checked

What do we know? There is ________ but no _________ .

voltagecurrent

A Tech 2 is used to trigger #6 injector, it is clear the computer can gg j , pfire the injector. The RPM inputs to the PCM are checked next.

CMP (in red) and DREF (in yellow) are added,CMP (in red) and DREF (in yellow) are added, CMP has no toggle and injectors are not firing!

Theory?

It was believed this engine would start gwithout a CMP input but that is not happening

The CMP is disconnected and the engine starts once but most often it will notstarts once, but most often it will not

The vehicle was setting a P0341 code and the other shop had already replaced the CMPthe other shop had already replaced the CMP with an aftermarket unit

A replacement CMP is ordered and installed The vehicle now starts every time over a two

day period

CMP is un-plugged engineCMP is un-plugged, engine starts!

Screen 1 of 2

Screen 2 of 2

Conclusion

Know your scope its capabilities andKnow your scope, its capabilities and limitations

Learn new techniques and develop new Learn new techniques and develop new testing strategiesM k t t h di i d Make one more test when diagnosing and test known good cars

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