P0647

P0647-A/C CONTROL CIRCUIT HIGH





For a complete wiring diagram Refer to Diagrams/Electrical.

Theory of Operation


"The clutch on the A/C compressor controls the drive of the Freon compressor. The clutch is driven by a signal from the TIPM. The TIPM receives a signal from the ECM. The ECM receives various information from the operator controls and A/C system to determine when the clutch should be turned on. The system will activate the A/C clutch during A/C or defrost use. You will not receive a MIL lamp for this fault, but the customer may complain of poor A/C performance."

- When Monitored:
When the ignition is on.

- Set Condition:
When the signal from the A/C Clutch output does not match the signal from the A/C Clutch feedback.







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


Diagnostic Test


1. (C13) A/C CLUTCH CONTROL CIRCUIT SHORTED TO EXTERNAL VOLTAGE




Ignition off.
Disconnect the C2 ECM and TIPM harness connectors.

NOTE: Check connectors - Clean/repair as necessary.

Ignition on, engine not running.
Using a Voltmeter, measure the voltage on the (C13) A/C Clutch Control circuit at the TIPM harness connector.
Is the voltage less than 1 volt?

Yes


- Go To 2


Yes


- Repair or Replace the wiring harness.
- Perform POWERTRAIN VERIFICATION TEST (DIESEL). Powertrain Verification Test



2. ECM




Ignition off.
Connect the C2 ECM and harness connector.
Ignition on, engine not running.
Using a 12-volt test light connected to ground, probe the (C13) A/C Clutch Control circuit at the TIPM connector while actuating the A/C Clutch with the scan tool.

NOTE: The test light must illuminate brightly.

Compare the brightness to that of a direct connection to the battery.
Does the test light illuminate brightly?

Yes


- Go To 3


No


- Replace the ECM.
- Perform POWERTRAIN VERIFICATION TEST (DIESEL). Powertrain Verification Test



3. TIPM
Using a back probing tool 6801, back probe the A/C clutch power circuit in the TIPM connector
Using a 12-volt test light connected to ground, probe C3 A/C Clutch Output Control at the TIPM connector while actuating the A/C Clutch Circuit with the scan tool.

NOTE: The test light must illuminate brightly.

Compare the brightness to that of a direct connection to the battery.
Does the test light illuminate brightly?

Yes


- Perform INTERMITTENT CONDITION (DIESEL) test.Intermittent Condition


No


- Replace the TIPM.
- Perform POWERTRAIN VERIFICATION TEST (DIESEL). Powertrain Verification Test