- Powertrain/On-Board Diagnostic System Check

OBD System Check Chart:

PCM Diagnostic Circuits:

DIAGNOSTIC SYSTEM CHECK
The on-board diagnostic system check must be the starting point for any driveability complaint diagnosis. Before using this you should perform a careful visual/physical check of the PCM and engine grounds for being clean and tight.

The on-board diagnostic system check is an organized approach to identifying a problem created by an electronic engine control system malfunction because it directs the service technician to the next logical step in diagnosing the complaint.

CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) 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. This test is to determine if the PCM can control the Malfunction Indicator Lamp (MIL) by using Tech 1 MIL system check.
3. If multiple DTCs are stored, start with the lowest numbered DTC first, unless DTC chart indicates not to.
4. 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 (i.e. advanced cam timing) may substantially alter sensor values.

If the actual data is not within the typical values established, the C-Charts will provide a functional check of the suspect component or system.

With key "ON," the MIL will flash for less than 1 second then remain "OFF" unless a DTC is "CURRENT" or a fault in the MIL circuit exists. if the MIL remains "OFF," cycle the ignition switch "OFF" and "ON" MIL should flash.