Component Tests and General Diagnostics

In the electronic control systems, momentary problems can occur in electronic circuits and input and output signals, and this can result in temporary trouble symptoms or a diagnostic trouble code being recorded by means of ECU on-board diagnostics. If the cause of the problem is continuous, the location of the abnormality can be discovered by checking according to the troubleshooting chart classified by trouble symptoms. However, the symptoms of some transient problems may return to normal by themselves, so there is a possibility that the cause of the problem will be unclear.

The causes of problems in vehicles which are malfunctioning "temporarily" (when trouble symptoms do not reoccur) are mainly vibrations, heat and excess electrical resistance. By carrying out inspection according to the simulation method given below, the trouble symptom can be made to reoccur.

Simulated Method

Test by the following method to check if the problem reoccurs.
1. When the main cause is probably vibration, proceed as follows:
a. Gently shake connector up, down, right and left.
b. Gently rock each sensor by hand.
c. Gently shake other moving parts.
2. When the main cause is probably heat, heat the component under suspicion to no more than 176°F.
3. When the main cause is probably excessive electrical resistance, turn all electrical switches, including the headlight and rear defogger.
4. If the trouble symptom does not reoccur even after performing these inspections, the problem should be left for a while.