P0688

P0688-ASD/MAIN SENSE CIRCUIT





For a complete wiring diagram Consult Diagrams/Electrical

- When Monitored:
With the control circuit active and battery voltage greater than 10.4 volts.

- Set Condition:
The PCM detects an open or shorted condition in the (F343) ASD Relay Output circuit.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.Initial Inspection and Diagnostic Overview

Diagnostic Test

1. DTC IS ACTIVE
Turn the ignition on.
With the scan tool, Clear DTCs in the Powertrain Control Module (PCM).
With the scan tool, actuate the Auto Shutdown (ASD) Relay Control State.
With the scan tool, select View DTCs.
Is the DTC Active at this time?

Yes

- Go to 2

No

- Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. Checking For An Intermittent DTC

2. FUSED B(+) CIRCUIT OPEN OR HIGH RESISTANCE
Turn the ignition off.
Remove the Auto Shutdown Relay.
Turn the ignition on.
Using a 12 volt test light connected to ground, check both Fused B(+) circuits in the Auto Shutdown Relay connector.

NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.

Is the test light illuminated and bright?

Yes

- Go to 3

No

- Repair the open or high resistance in the Fused B(+) circuit.
- Perform the PCM Verification Test. Powertrain Verification Test

3. (F343) ASD RELAY OUTPUT CIRCUIT SHORTED TO VOLTAGE
Turn the ignition off.
Disconnect the Powertrain Control Module (PCM) connectors.
Turn the ignition on.
Measure the voltage of the (F343) ASD Relay Output circuit in the Auto Shutdown Relay connector.
Is there any voltage present?

Yes

- Repair the short to voltage in the (F343) ASD Relay Output circuit.
- Perform the PCM Verification Test. Powertrain Verification Test

No

- Go to 4

4. (F343) ASD RELAY OUTPUT CIRCUIT SHORTED TO GROUND
Measure the resistance between ground and the (F343) ASD Relay Output circuit in the Auto Shutdown Relay connector.
Is the resistance below 100 ohms?

Yes

- Repair the short to ground in the (F343) ASD Relay Output circuit.
- Perform the PCM Verification Test. Powertrain Verification Test

No

- Go to 5

5. (F343) ASD RELAY OUTPUT CIRCUIT OPEN OR HIGH RESISTANCE
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 (F343) ASD Relay Output circuits between the Auto Shutdown Relay connector and each of the appropriate terminals of special tool #8815.
Is the resistance below 5.0 ohms?

Yes

- Go to 6

No

- Repair the open or high resistance in the (F343) ASD Relay Output circuit.
- Perform the PCM Verification Test. Powertrain Verification Test

6. AUTO SHUTDOWN RELAY
Turn the ignition off.
Install the Auto Shutdown Relay.
Connect the C3 Powertrain Control Module (PCM) harness connectors.

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 along with the #8815-1 to perform the diagnosis.

Turn the ignition on.
With the scan tool, actuate the Auto Shutdown (ASD) Relay Control State.
Measure the voltage of each of the (F343) ASD Relay Output circuits in the appropriate terminals of special tool #8815-1.

NOTE: If the DTC is active, the actuation test may not be allowed by the PCM. If may be necessary to clear the DTCs before starting the actuation.

NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.

Is the test light illuminated and bright for each of the circuits during the actuation?

Yes

- Go to 7

No

- Replace the Auto Shutdown Relay.
- Perform the PCM Verification Test. Powertrain Verification Test

7. POWERTRAIN CONTROL MODULE (PCM)
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Auto Shutdown Relay and the Powertrain Control Module (PCM).
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out or corroded terminals.
Search for any Technical Service Bulletins that may apply.
Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test. Powertrain Verification Test

No

- Replace and program the Powertrain Control Module (PCM).
- Perform the PCM Verification Test. Powertrain Verification Test