Description and Use

DIAGNOSIS
These engines have controls to reduce exhaust emissions, while maintaining good driveability and fuel economy.

A Powertrain Control Module (PCM) is the main control system and constantly monitors sensors used to provide information about engine operation and the various systems.

The PCM has the ability to perform some diagnosis of itself, and of other parts of the system. When a fault is detected, it lights a Malfunction Indicator Lamp (MIL) "Service Engine Soon" on the instrument panel and a Diagnostic Trouble Code (DTC) will be stored in the PCM's memory. This does not mean that the engine should be stopped right away, but that the cause of the lamp coming "ON" should be checked as soon as reasonably possible.

Diagnostic charts incorporate diagnosis procedures using a scan tool, such as the Tech 1, where possible. The scan tool has the ability to save time in diagnosis and prevent the replacement of good parts. The key to using the scan tool successfully for diagnosis lies in the technician's ability to understand the system being diagnosed, as well as an understanding of the scan tool's limitations. Refer to Vehicle On-Board Diagnosis for more information. Testing and Inspection