2007 Compass Patriot MK Factory Service Manual 9 - ENGINE

P0645-A/C CONTROL CIRCUIT/OPEN





For a complete wiring diagram Refer to Section 8W



Possible Causes
  
INTERMITTENT DTC
  
(C27) A/C COMPRESSOR CONTROL CIRCUIT SHORTED TO VOLTAGE
  
(C27) A/C COMPRESSOR CONTROL CIRCUIT SHORTED TO GROUND
  
(C27) A/C COMPRESSOR CONTROL CIRCUIT OPEN OR HIGH RESISTANCE
  
(Z916) GROUND CIRCUIT OPEN OR HIGH RESISTANCE
  
A/C COMPRESSOR
  
POWERTRAIN CONTROL MODULE (PCM)
  

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - STANDARD PROCEDURE)



Diagnostic Test

1. DTC IS ACTIVE

Start the engine and allow it to reach normal operating temperature.
Turn the Air Conditioning on.

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.


With the scan tool, select View DTCs.

Is the status Active for this DTC?

Yes


No

2. (Z916) GROUND CIRCUIT OPEN OR HIGH RESISTANCE



Turn the ignition off.
Disconnect the A/C Compressor connector.
Turn the ignition on.
Using a 12 volt test light connected to 12 volts, check the (Z916) Ground circuit in the A/C Compressor harness 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


No

3. (C27) A/C COMPRESSOR CONTROL CIRCUIT SHORTED TO VOLTAGE



Turn the ignition off.
Disconnect the Powertrain Control Module (PCM) connector.
Turn the ignition on.
Measure the voltage of the (C27) A/C Compressor Control circuit in the A/C Compressor harness connector.

Is there any voltage present?

Yes


No

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



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

Is the resistance below 100 ohms?

Yes


No

5. (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 Powertrain Control Module (PCM) harness connector.

Is the resistance below 5.0 ohms?

Yes


No

6. A/C COMPRESSOR



Connect the Powertrain Control Module (PCM) connector.
Turn the ignition on.
With the scan tool, actuate the A/C Compressor control to the ON position.
Using a 12 volt test light connected to ground, check the (C27) A/C Compressor Control circuit in the A/C Compressor harness connector.

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


With the scan tool, actuate the A/C Compressor control to the OFF position.
Using a 12 volt test light connected to ground, check the (C27) A/C Compressor Control circuit in the A/C Compressor harness connector.

NOTE: The test light should not be illuminated.



Is the test light illuminated and bright with the actuation ON (100%) and not illuminated with the actuation OFF (0%)?

Yes


No

7. POWERTRAIN CONTROL MODULE (PCM)

Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the A/C Compressor 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.
Refer to any Technical Service Bulletins that may apply.

Were any problems found?

Yes


No