Diagnostic Procedure Use

The diagnostic procedures used in this section are designed to find and repair problems that relate to the transmission controls system. The general approach is to find the appropriate diagnosis for a problem by using the basic steps described below.

1. Understand the customer's complaint. It is critical that the technician understands what the customer's complaint is. Failure to understand the customer's complaint may lead to misdiagnosis or an unnecessary diagnosis. Among other things, the technician must know whether the condition is present at all times, only under certain circumstances, or truly intermittent (random). This will assist the technician in duplicating and diagnosing the problem. Another reason that the technician must understand the customer's complaint is so that the technician may determine whether the complaint requires service or if the vehicle operation is normal. Trying to diagnose a complaint that is normal will waste time and may result in unnecessary service.
2. Are the Diagnostics working properly? If the Engine MIL illuminates, start with the Powertrain OBD System Check in Engine Controls. If only the Service Transmission Lamp (STL) is illuminated, start with the TRANSMISSION ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK.
3. Are the DTCs displayed? If a DTC is identified by the diagnostics, the OBD SYSTEM CHECK will direct you to the appropriate chart.