Orlando

DTC P0645, P0646, or P0647

When the A/C switch is pressed, the HVAC control module sends an A/C request message to the engine control module (ECM) via CAN-Bus. Therefore, the ECM grounds the A/C compressor clutch relay control circuit, which will switch the A/C compressor clutch relay. With the relay contacts closed, battery voltage is supplied to the A/C compressor clutch. The A/C compressor clutch will be activated.

P0645 or P0646

The ECM detects a short to ground or an open at the A/C compressor clutch relay control circuit.

P0647

The ECM detects a short to voltage at the A/C compressor clutch relay control circuit.

P0645 or P0646

The A/C compressor is inoperative or always active.

P0647

The A/C compressor is inoperative.

The condition for setting the DTC is no longer present.

Schematic Reference

HVAC Schematics : Automatic

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Ignition OFF, remove the KR29 A/C Compressor Clutch Relay.
2. Ignition ON, test for greater than 11 V between the ignition circuit terminal 86 at the KR29 A/C Compressor Clutch Relay and ground.

⇒	If less than 11 V

Repair the open/high resistance in the circuit.

⇓	If greater than 11 V

3. Ignition OFF, disconnect the X2 harness connector at the K20 Engine Control Module.
4. Ignition ON, test for less than 0.3 V between the control circuit terminal 85 at the KR29 A/C Compressor Clutch Relay and ground.

⇒	If greater than 0.3 V

Repair the short to voltage on the circuit.

⇓	If less than 0.3 V

5. Ignition OFF, test for infinite resistance between the control circuit terminal 85 at the KR29 A/C Compressor Clutch Relay and ground.

⇒	If less than infinite resistance

Repair the short to ground on the circuit.

⇓	If infinite resistance

6. Test for less than 5 Ω between the KR29 A/C Compressor Clutch Relay control circuit terminal 85 and the appropriate control circuit terminal at the K20 Engine Control Module harness connector listed below:

•	Terminal 91 X2 with 2H0

•	Terminal 31 X1 with LAF

•	Terminal 30 X1 with LBN

•	Terminal 41 X2 with LNP

⇒	If greater than 5 Ω

Repair the open/high resistance in the circuit.

⇓	If less than 5 Ω

7. Replace the KR29 A/C Compressor Clutch Relay and verify the DTC does not reset.

⇒	If DTC resets

Replace the K20 Engine Control Module.

⇓	If DTC does not reset

8. All OK.

Static Test

1. Ignition OFF, disconnect the KR29 A/C Compressor Clutch Relay.
2. Test for 60-180 Ω between the B+ terminal 85 and the control terminal 86 of the KR29 A/C Compressor Clutch Relay.

⇒	If not within 60-180 Ω

Replace the KR29 A/C Compressor Clutch Relay.

⇓	If within 60-180 Ω

3. Test for the resistance between the following terminals:

•

30 and 86

•

30 and 87

•

30 and 85

•

85 and 87

⇒	If less than infinite resistance

Replace the KR29 A/C Compressor Clutch Relay.

⇓	If infinite resistance

4. All OK.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for engine control module replacement, setup, and programming