Diagnostic Circuit Check
Diagnostic Circuit CheckOBD Chart - Part 1 0f 2:
OBD Circuit - Part 2 Of 2:
OBD Circuit:
Circuit Description
The OBD System Check is an organized approach to identifying a malfunction created by the electronic engine control system. 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.
Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.
1. Checks the MIL operation with the ignition switch in the "ON" position.
2. Checks to see if the ECM's normal diagnostic mode is functioning.
3. Checks to see if the ECM's test diagnostic mode is functioning.
4. Checks to see if the vehicle will start.
5. Checks for any DTCs that are stored in the ECM's memory with the engine running.
6. Checks for any DTCs that are stored in the ECM's memory with the engine off.
7. Checks to see if DTC 51 is functioning normally.
8. Checks to see if DTCs that were stored are intermittent malfunctions.