Powertrain OBD System Check

Powertrain OBD System Check

Important: Understanding the table and using it correctly will reduce diagnosis time and prevent the unnecessary replacement of parts.

The Powertrain OBD System Check is an organized approach for identifying a problem. After the visual inspection is complete, the Powertrain OBD System Check should be performed. This Powertrain System Check will provide direction for diagnosis of the following items:
^ A faulty or inoperative PCM
^ No serial data
^ Malfunction indicator lamp (MIL) inoperative
^ PCM DTCs
^ Fuel system rich or lean
^ Customer complaint driveability symptoms

The Powertrain OBD System Check is designed as a master table for driveability and emissions system diagnosis. The system check should always be used as the starting point for all engine control system diagnosis.

Diagnostic Procedure Use
The diagnostic procedures used are designed to find and repair powertrain related problems. The general approach is to find the appropriate diagnosis for a problem with five basic steps described below.
1. Understand the customers concerns. It is critical that the technician understand what the customers concern is. Failure to understand the customer concern may lead to misdiagnosis or unnecessary diagnosis. The technician must know whether the condition causing the customer's concerns is present at all times, only under certain circumstances, or intermittent (random). This knowledge will assist the technician in duplicating and diagnosing the problem. Understanding the customers concern enables the technician to determine whether the condition requires service or is a characteristic of normal vehicle operation. Trying to diagnose a customer concern that is a normal characteristic of vehicle operation will waste time and may result in unnecessary service.
2. Are the diagnostics built into the PCM working properly? Use the Powertrain OBD System Check. This is the starting point for the diagnostic procedure, always begin here.
3. Are DTCs displayed? If a DTC is identified by diagnostics, the Powertrain OBD System Check will direct you to the appropriate table.
4. Is the customer's concern related to a specific powertrain subsystem? If no related DTCs are set, the next quickest way to locate the problem is to narrow it down to a specific powertrain subsystem. If a specific subsystem can be pinpointed as the cause, diagnosis will be quicker and easier.
5. Is the customer's concern powertrain related? Some customer concerns may appear to be powertrain related but are actually caused by other vehicle systems.