- Powertrain/On-Board Diagnostic System Check

On Board Diagnostic (OBD) System Check:

PCM Power Supply,MIL And DLC Circuits:

CIRCUIT DESCRIPTION
The On-Board Diagnostic (OBD) system check is an organized approach to identifying a problem created by an electronic engine control system malfunction. It must be the starting point for any driveability complaint diagnosis, because it directs the service technician to the next logical step in diagnosing the complaint. Understanding the chart and using it correctly will reduce diagnostic time and prevent the unnecessary replacement of good parts.

CHART TEST DESCRIPTION
The numbers below refer to circled numbers on the diagnostic chart.

1. This step is to determine if the Tech 1 can establish communication with the Powertrain Control Module (PCM). If there is no communication between the PCM and the Tech 1, no data will be displayed.
2. Comparison of actual control system data with the typical values is a quick check to determine if any parameter is not within limits. Keep in mind that a base engine problem may substantially alter sensor values.
3. Installation of a scan tool can provide a ground path for the PCM and may hide a driveability complaint due to otherwise poor PCM grounds. Refer to "PROCEDURES/DIAGNOSIS BY SYMPTOM" for assistance in repairing difficult to diagnose or intermittent problems. Testing and Inspection
4. If multiple DTCs are stored, start with the lowest numbered DTC first, unless DTC chart indicates not to.
5. If scan data values are out of normal range, refer to "PROCEDURES/DIAGNOSTIC CHARTS" and see diagnostic charts listed under "A-CHARTS" and "C-CHARTS", for system or component diagnosis of the specified component or related system. Testing and Inspection

DIAGNOSTIC AIDS
This vehicle is equipped with a Powertrain Control Module utilizing Electrically Erasable Programmable Read Only Memory (EEPROM).
^ When diagnostics call for replacement of the PCM the new PCM must be programmed. Refer to POWERTRAIN CONTROL MODULE.