General Information

INTRODUCTION: HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS:

GENERAL INFORMATION
- A large number of ECU controlled systems are used in the LEXUS RX400H. In general, ECU controlled systems are considered to be very intricate, requiring a high level of technical knowledge to troubleshoot. However, most problem checking procedures only involve inspecting the ECU controlled system's circuits one by one. An adequate understanding of the system and a basic knowledge of electricity is enough to perform effective troubleshooting, accurate diagnoses and necessary repairs.
- (When using Techstream*)
HINT: *: Techstream is the name for the diagnostic tester in North America.

- Before using Techstream, read the operator's manual thoroughly.
- If Techstream cannot communicate with the ECU controlled systems when connected to the DLC3 with the ignition switch on and Techstream turned on, there is a problem on the vehicle side or Techstream side.
1 If communication is possible when the Techstream is connected to another vehicle, inspect the diagnosis data link line (Bus "+" line), CANH and CANL lines, and the power circuits for the vehicle ECUs.
2 If communication is still not possible when Techstream is connected to another vehicle, the problem is probably in the tester itself. Consult the Service Department listed in Techstream's instruction manual.