General Information

There are many ECU controlled systems used in LEXUS GX470. In general, ECU controlled system are considered to be very intricate and require a high level of technical knowledge and expert skill to troubleshoot. The fact is, however, that if you proceed by inspecting the circuits one by one, troubleshooting of these systems is not complex. If you have adequate understanding of the system and basic knowledge of electricity, the problem can be accurately diagnosed and fixed. This article is designed based on the above principle to help service technicians perform accurate and effective troubleshooting, and is compiled for the following major ECU controlled systems:

The troubleshooting procedures are described on the following tables.

FOR USING OBD SCAN TOOL OR HAND-HELD TESTER 

• Before using the scan tool or tester, the scan tool's instruction book or tester's operator article should be read thoroughly.
• If the scan tool or tester cannot communicate with the 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 (Bus (+)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 outlined in the Tester Operator's article.