How to Troubleshoot ECU Controlled Systems

GENERAL INFORMATION

A large number of ECU controlled Systems are used in LEXUS. 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. The fact is, however, 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. This manual is designed through emphasis of the above standpoint to help service technicians perform an accurate and effective troubleshooting, and is compiled for the following major ECU controlled systems:
The troubleshooting procedure and how to make use of it are described.

System
1. SFI System
2. Electronic Modulated Suspension System
3. ABS with EBD System
4. ABS with EBD & BA & TRAC & VSC System
5. Electronic controlled Automatic Transmission [ECT]
6. Air conditioning System
7. Supplement Restraint System
8. Lighting System
9. wiper and Washer System
10. Audio System
11. LEXUS Navigation System
12. Power Window control System
13. Power Mirror control System
14. Combination Meter
15. Front Power Seat control System (with memory)
16. Power Door Lock control System
17. Wireless Door Lock control System
18. Luggage Comportment Door Opener System
19. Key Unlock Warning System
20. Engine immobilizer System
21. Theft Deterrent System
22. Multiplex Communication System
23. Cruise Control System

FOR USING SCAN TOOL OR HAND-HELD TESTER

HINT:
- Before using the tester, the tester's operator manual should be read thoroughly.
- If the tester cannot communicate with ECU controlled systems when you have connected the cable of the tester to the DLC3 with the ignition switch and tester turned ON, there is a problem on the vehicle side or tester side.

1. If the communication is normal when the tester is connected to another vehicle, inspect the diagnosis data link line (Busy-line) or ECU power circuit of the vehicle.
2. If the communication is still impossible when the tester is connected to another vehicle, the problem is probably in the tester itself, so perform the Self Test procedures outline in the Tester Operator's Manual.