ENGINE CONTROLS PART #4 - DIAGNOSIS

System Diagnosis and Troubleshooting

An Overview of the Self Diagnostic System

When the ECU detects a problem, it can turn on the check engine light to alert the driver that a fault exists in the system. At the same time, the ECU registers a diagnostic code in its keep alive memory so that the faulty circuit can be identified by a service technician at a later time.

发动机控制部分 #4- 诊断

系统诊断和故障排除

自诊断系统概述

当电脑发现故障，检查发动机指示灯点亮警示驾驶员系统存在故障。同时，电脑在存储器里记录故障码以便技术服务人员稍后可以查处故障回路。

Fault Detection Principles故障检测原则

故障检测范围

温度信号电压

不正常检测范围

自诊断系统正常变化

冷却剂温度

正常范围

Limitations of the Self Diagnostic System

•The ECU must see a signal in an abnormal range for more than a given amount of time before it will judge that signal to be faulty. Therefore, many intermittent problems cannot be detected by the ECU.

•When the ECU stores a diagnostic code, the code indicates a problem somewhere in the sensor circuit, not necessarily in the sensor itself Further testing is always required to properly diagnose the circuit.

自诊断系统的局限性

电脑只有在一定时间以上检测到一个不正常信号才可以判断这个信号是故障信号。因此，许多间歇性的故障不能被识别 。

当电脑储存了一个故障码，这个码显示传感器电路的某些部位有故障，不一定传感器自身有故障。精确诊断该回路需要更进一步的检测。

•Not all circuits are monitored by the ECU. Just because the ECU generates a normal code does not mean that there are no problems within the electronic control system.

•Occasionally, diagnostic codes can be set during routine service procedures or by problems outside the electronic control system. Always clear codes and confirm that they reset prior to circuit troubleshooting.

不是所有电路都被电脑监控。仅仅电脑发出了正常码不意味着控制电路就没有问题。

偶尔，诊断代码可以在日常维护过程中或由电子控制系统以外的故障引起。在电路故障诊断之前必须要进行清码并确认码已经被重新设置。

Four Systematic Steps In Diagnosis

•Routine Quick Checks

•Use of the Self Diagnostic System

•Troubleshooting by Symptom

•Quality Control Check

四个系统性的诊断步骤常规快速检验

自诊断系统的使用

通过迹象排除故障

质量控制检测

Procedures to Retrieve Trouble Codes故障码拾取的步骤

检查端子

检查发动机连接口

To enter engine diagnostics:

•Locate the check connector under the hood and identify the T (TE1 on late model TCCS) and E1 terminals.

•Turn the ignition switch to the "on" position and make sure that the check engine light is on.

•Confirm that the throttle is closed (IDL contact on).•Jumper check connector terminals T (TE1) to E1.

进入发动机诊断

确定发动机罩下检查接口的位置和识别 T 和 E1 端子

打开点火点开关到‘ ON’ 位置并确保检查发动机灯打开

确认节气门关闭

跨线连接 T 和 E1 的 接线端子

2 位 - 数字码1 位 - 数字

码

故障码12 和 23 显示

故障码 2 和 3 显示

超级显示器显示

正常

错误

Erasing Long Term Memory清除长期存储

读并记录故障码

识读和确认故障码

码11 ， 13 ， 42

码 51

到有关诊断码图

清除记忆；看是否以前的输出码仍被输出

检查步骤

选挡杆处在 P 或A

节气门完全关闭

空气调节器开关关

以前的输出码仍被输出

排除间歇性故障

到有关诊断码图

轻微的摇动松

轻微的晃动

间歇检修

紧

端子伸长

故障

Monitored and Non-monitored Circuits

Although the newer TCCS self diagnostic system is getting more sophisticated every model year, there are still many electronic control system circuits which the ECU does not monitor. Generally speaking, most input sensors are monitored for faults, but most output actuators are not. Exceptions to this are the Neutral Start Switch (NSW) and Power Switch (PSW)* input signals which are not monitored. Codes 25 and 26 monitor the air/fuel ratio rather than the status of a particular circuit.

有监控和无监控电路

虽然新的 TCCS 自诊断系统每一年都在变的更加复杂，但仍有很多电控系统电路电脑不能监控。概括来说，更多内部传感器被监控，但大多执行器不是。除此之外空档启动开关和功率开关输入信号也不被监控，码 25 和 26 监控空燃比而非特定电路的状态。

Troubleshooting AfterCode Retrieval

To find the appropriate diagnostic procedure to follow:•Refer to the last column of the repair manual "Diagnostic Codes" list.

•This will lead to one or more "Troubleshooting with a Voltmeter/Ohmmeter" diagnostic charts which will facilitate circuit diagnosis.

•This may also lead to an "Inspection of Component" procedure which will facilitate diagnosis of the sensor or actuator in the circuit.

提码后的故障诊断

按照如下步骤找到合适的诊断程序

参考维修手册“自诊断码”表最后一栏。

这将引导出一个或更多“用电压表或欧姆表进行故障诊断”的诊断图，它将使电路的 诊断更方便。

这也可能引导出一个 “根据症状进行检测”的步骤，它将使电路中传感器或执行器的 诊断更方便。

拾取故障码

用电压、欧姆表排除故障表

问题辨别根据症状检查表

But what if you do not have a diagnostic code to help lead you to the cause of the customer complaint? What do you do next? Before we address the third step in the systematic diagnostic approach, the subject of aninoperative self diagnostic system must be addressed.

但是假如你不能获得故障码的帮助而得到消费者的抱怨，下一步该怎么做？在我们陈述系统性诊断步骤中的第三步之前，无效自诊断系统这一主题必须被说明。

No Self Diagnostic System Output (Use of Diagnostic Circuit Inspection Schematic)

检查连接器

电控保险 传感器

电控继电器

没有自诊断系统输出电路

自诊断电路检查图

示

自诊断电路检查

检测灯

5V 调节器

微处理器

Toyota Diagnostic Communications Link (TDCL)

丰田自诊断通信联系检查连接器

自诊接口