P0646

P0646-A/C CONTROL CIRCUIT LOW

For a complete wiring diagram, refer to the Wiring Information.





- When Monitored:
With the engine running. A/C Compressor is off.

- Set Condition:
The PCM detects that the A/C Compressor control circuit voltage is below the minimum acceptable value.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

Diagnostic Test

1. DTC IS ACTIVE

NOTE: If there are any ASD/Main Relay or system voltage DTCs present, diagnose those DTCs before proceeding with this test procedure.

1. Ignition on, engine not running.
2. With the scan tool, select View DTCs. Copy DTC and Freeze Frame information and clear DTCs.

NOTE: Active or pending DTCs may not allow A/C Relay actuation, make sure all DTCs are cleared before proceeding with this test procedure.

3. With the scan tool, actuate the A/C Relay.
4. Monitor the scan tool for at least two minutes.
5. With the scan tool, select View DTCs.

Is the status Active for this DTC?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test.

2. A/C CLUTCH RELAY
1. Turn the ignition off.
2. Install a known good relay.
3. With the scan tool actuate the A/C Relay, cycling between on and off.
4. Monitor the scan tool for at least two minutes.
5. With the scan tool, select View DTCs.

Is the DTC active at this time?

Yes

- Go To 3

No

- Replace the A/C Clutch Relay.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

3. CHECK THE (C13) A/C CLUTCH CONTROL CIRCUIT FOR A SHORT TO GROUND
1. Turn the ignition off.
2. Remove the A/C Relay.
3. Disconnect the Powertrain Control Module (PCM) C1 harness connector.
4. Measure the resistance between ground and the (C13) A/C Clutch Control circuit at the PCM C1 harness connector.

Is the resistance above 10k Ohms?

Yes

- Go To 4

No

- Repair the (C13) A/C Clutch Control circuit for a short to ground.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

4. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Relay and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the related connectors.
4. Perform any Technical Service Bulletins that may apply.

Were any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

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