P0688-AUTO SHUTDOWN RELAY SENSE CIRCUIT LOW
For a complete wiring diagram Refer to Section 8W.
- When Monitored:
With ignition key on. Battery voltage greater than 10 volts.
- Set Condition:
No voltage sensed at the PCM when the ASD relay is energized. One Trip Fault. Three good trips to turn off the MIL.
| Possible Causes |
| (A924) FUSED B+ CIRCUITS |
| (A142) ASD RELAY OUTPUT CIRCUIT OPEN |
| ASD RELAY |
| PCM |
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).
Diagnostic Test
1. VERIFY ASD DTCNOTE: Diagnose P0685 - Auto Shutdown Relay Control Circuit first if it set along with this DTC.
With a scan tool, erase the DTC.
Attempt to start the engine. If the engine will not start, crank the engine for at least 15 seconds. It may be necessary to repeat several times.
Does the DTC reset?
Yes
- Go To 2
No
- Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
2. ENGINE OPERATION
Attempt to start the engine.
Does the engine start?
Yes
- Go To 3
No
- Go To 4
3. (A142) ASD RELAY OUTPUT CIRCUIT OPEN
Turn the ignition off.
Remove the ASD Relay.
Disconnect the C3 PCM harness connector.
CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.
Measure the resistance of the (A142) ASD Relay Output circuit from the Relay connection to the appropriate terminals of special tool #8815.
Is the resistance below 5.0 ohms?
Yes
- Go To 7
No
- Repair the open in the (A142) ASD Relay Output circuits.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
4. ASD RELAY
Turn the ignition off.
Install a substitute relay in place of the ASD Relay.
Ignition on, engine not running.
With a scan tool, erase DTCs.
Attempt to start the engine.
With a scan tool, select View DTCs.
Does the DTC reset?
Yes
- Go To 5
No
- Replace the ASD Relay.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
5. (A924) FUSED B+ CIRCUITS
Turn the ignition off.
Using a 12-volt test light connected to ground, probe the (A924) Fused B+ circuits at the Relay connection.
Does the test light illuminate brightly?
Yes
- Go To 6
No
- Repair the open or short to ground in the (A924) Fused B+ circuits. Inspect the related fuse and repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
6. (A142) ASD RELAY OUTPUT CIRCUIT OPEN
Disconnect the C3 PCM harness connector.
CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.
Measure the resistance of the (A142) ASD Relay Output circuit from the Relay connection to the appropriate terminals of special tool #8815.
Is the resistance below 5.0 ohms?
Yes
- Go To 7
No
- Repair the open in the (A142) ASD Relay Output circuit.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
7. PCM
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.
Were there any problems found?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
- Replace and program the Powertrain Control Module per Service Information.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)