IN−22 − INTRODUCTION HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS GENERAL INFORMATION A large number of ECU controlled systems are used in the 1999 LEXUS LX470. In general, the ECU con- trolled 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, trouble- shooting 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 accurate and effective troubleshooting, and is compiled for the following major ECU controlled sys- tems: The troubleshooting procedure and how to make use of it are described on the following pages. IN087−03 FOR USING OBD II SCAN TOOL OR LEXUS 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 DLC3, turned the ignition switch ON and operated the scan tool, 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 (Bus 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. 22 Author : Date: System Page 1. Engine DI−1 2.
Automatic Transmission DI−162 3. Active Height Control Suspension & Adaptive Variable Suspension DI−230 4. ABS & Hydraulic Brake Booster Power Supply System DI−324 5. Power Tilt and Power Telescopic Steering Column DI−413 6. Supplemental Restraint System DI−447 7. Power Seat Control System DI−562 8. Wireless Door Lock Control System DI−581 9. Theft Deterrent System DI−616 10. Cruise Control System DI−658 11. Engine Immobiliser System DI−682 12. Body Control System DI−696 13. Multiplex Communication System DI−744 14. Air Conditioning System DI−765