Test Description: Notes

The numbers below refer to the step numbers in the diagnostic table.

1. 3. This step checks whether the scan tool can communicate with other control modules on the vehicle. If the scan tool can communicate with one of the other modules then the DLC connector, the shared circuits, and the scan tool are OK.
2. 5. The modules supply a low current, about 1.85 mA, voltage on the serial data circuit. The normal circuit low current will NOT illuminate a test lamp.

   If the circuit is shorted to battery positive the higher current will illuminate the test lamp.

3. 7. If the engine starts and runs, the main relay is OK.
4. 8. This step checks whether the PCM is receiving ignition positive voltage from the IG fuse located in the Junction Block. The main relay will not energize and the PCM can not provide serial data without ignition positive voltage from the IG fuse circuit.
5. 9. This step checks whether the PCM is receiving ignition positive voltage from the main relay when the ignition is ON. The PCM can not provide serial data without ignition positive voltage from the main relay.
6. 10. The PCM can not provide serial data without the correct power and grounds.
7. 14. The scan tool may be damaged by high current flow on the serial data circuit at DLC terminal 7.

   Check the scan tool for proper operation on a known good vehicle that uses terminal 7 of the DLC for serial data communication.