2007 Compass Patriot MK Factory Service Manual 9 - ENGINE

P0646-A/C CLUTCH CONTROL CIRCUIT LOW

For a complete wiring diagram Refer to Section 8W

When Monitored:
With the ignition on and the A/C Compressor command off.
Set Condition:
The ECM detects a short to ground on the (C27) A/C Compressor Control circuit for 0.48 seconds.

Possible Causes

INTERMITTENT DTC

(C27) A/C COMPRESSOR CONTROL CIRCUIT SHORTED TO GROUND

(C27) A/C COMPRESSOR CONTROL CIRCUIT OPEN OR HIGH RESISTANCE

ENGINE CONTROL MODULE (ECM)

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

Diagnostic Test

1. DTC IS ACTIVE

Ignition on, engine not running.
With the scan tool, clear DTCs in the Engine Control Module (ECM).
With the scan tool, actuate the A/C Compressor.
Monitor the scan tool for at least two minutes.
With the scan tool, select View DTCs.

Is the status Active for this DTC?

Yes

Go To 2

No

Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

2. (C27) A/C COMPRESSOR CONTROL CIRCUIT SHORTED TO GROUND

Turn the ignition off.
Disconnect the A/C Compressor harness connector.
Disconnect the Engine Control Module (ECM) harness connector.
Measure the resistance between ground and the (C27) A/C Compressor Control circuit in the A/C Compressor harness connector.

Is the resistance below 1000.0 ohms?

Yes

Repair the (C27) A/C Compressor Control circuit for a short to ground.

Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

No

Go to 3

3. (C27) A/C COMPRESSOR CONTROL CIRCUIT OPEN OR HIGH RESISTANCE

Measure the resistance of the (C27) A/C Compressor Control circuit between the A/C Compressor harness connector and the Engine Control Module (ECM) harness connector.

Is the resistance below 10.0 ohms?

Yes

Go to 4

No

Repair the (C27) A/C Compressor Control circuit for an open circuit or high resistance.
Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

4. A/C COMPRESSOR

Connect the Engine Control Module (ECM) harness connector.
Turn the ignition on.
With the scan tool, Clear DTCs.
With the scan tool, actuate the A/C Compressor.
Monitor the scan tool for at least two minutes.
With the scan tool, select View DTCs.

Is the status Active for this DTC?

Yes

Go to 5

No

Replace the A/C Compressor in accordance with the Service Information.
Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

5. ENGINE CONTROL MODULE (ECM)

Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the A/C Compressor and the Engine Control Module (ECM).
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out or corroded terminals.
Refer to any Technical Service Bulletins that may apply.

Were any problems found?

Yes

Repair as necessary.

Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

No

Replace the Engine Control Module (ECM) in accordance with the Service Information.
Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)