How to Troubleshoot ECU Controlled Systems

HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS / GENERAL INFORMATION

A large number of ECU controlled Systems are used in TOYOTA cars and trucks. In general, the ECU controlled system is considered to be a very intricate system requiring a high level of technical knowledge and expert skill to troubleshoot.

However, the fact is that if you proceed to inspect the circuits one by one, troubleshooting of these systems is not complex. If you have adequate understanding of the system and a basic knowledge of electricity, accurate diagnosis and necessary repair can be performed to locate and fix the problem.

The diagnostic procedures are designed through emphasis of the above standpoint to help service technicians perform accurate and effective troubleshooting, and is compiled for the ECU controlled systems.


FOR USING OBD II SCAN TOOL OR TOYOTA HAND-HELD TESTER
Before using the scan tool or tester, the scan tool's instruction book or tester's operator manual should be read thoroughly.

If the scan tool or tester cannot communicate with ECU controlled systems when you have connected the cable of the scan tool or tester to the DLC, turned the ignition switch ON and operated the scan tool properly, there is a problem on the vehicle side or tool side.

1. If communication is normal when the tool is connected to another vehicle, inspect the diagnosis data link line (Buse line) or ECU power circuit of the vehicle.

2. If communication is still not possible when the tool is connected to another vehicle, the problem is probably in the tool itself, so perform the Self Test procedures outline in the Tester Operator's Manual.