How To Use OEM Diagnostic Procedures

HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS





A large number of ECU controlled systems are used in the LAND CRUISER. 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. This manual is designed through emphasis of the above standpoint to help service technicians perform accurate and effective troubleshooting, and is compiled for the major ECU controlled systems, listed above.

HOW TO PROCEED WITH TROUBLESHOOTING

Carry out troubleshooting in accordance with the procedures listed below. Here, only the basic procedure is shown. Details are provided in each section, showing the most effective methods for each circuit. Confirm the troubleshooting procedures first for the relevant circuit before beginning troubleshooting of that circuit.





[1]
Ask the customer about the conditions and the environment when the problem occurred.

[2] [3]
Confirm the symptoms and the problem conditions, and check the diagnostic trouble codes. (When the problem symptoms do not appear during confirmation, use the symptom simulation method described later on.)

[4] [5] [6]
Check the results obtained in Step [2] then confirm the inspection procedure for the system or the part which should be checked using the diagnostic trouble code chart or the matrix chart of problem symptoms.

[7]
Check and repair the affected system or part in accordance with the instructions in Step [6].

[8]
After completing repairs, confirm that the problem has been eliminated. (If the problem is not reproduced, perform the confirmation test under the same conditions and in the same environment as when it occurred for the first time.)





Taking into account the above points, a flow chart showing how to proceed with troubleshooting using the diagnostic trouble code check is shown above. This flow chart shows how to utilize the diagnostic trouble code check effectively, then by carefully checking the results, indicates how to proceed either to diagnostic trouble code troubleshooting or to troubleshooting of problem symptoms.