HVAC - Manual
DTC P0645, P0646, or P0647
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC P0645
-
Air Conditioning (A/C) Compressor Clutch Relay Control Circuit
DTC P0646
-
Air Conditioning (A/C) Compressor Clutch Relay Control Circuit Low Voltage
DTC P0647
-
Air Conditioning (A/C) Compressor Clutch Relay Control Circuit High Voltage
Diagnostic Fault Information
Circuit/System Description
The A/C compressor is belt driven and operates when the magnetic clutch is engaged. When the A/C switch is pressed, the HVAC control module sends an A/C request message to the 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.
The performance of the A/C compressor is regulated per a lifting magnet in the A/C compressor. The HVAC control module supplies battery voltage to the A/C compressor. When the A/C switch is pressed, the HVAC control module provides a pulse width modulation (PWM) signal to the A/C compressor in order to command the performance of the A/C compressor. The performance of the A/C compressor is regulated according to adjusted interior temperature on the basis of characteristic lines. Therefore the HVAC control module grounds the A/C compressor with the PWM signal.
Conditions for Running the DTC
* Engine is running.
* The HVAC control module is ON.
* The A/C switch is active.
Conditions for Setting the DTC
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.
Action Taken When the DTC Sets
P0645 or P0646
The A/C compressor is inoperative or always active.
P0647
The A/C compressor is inoperative.
Conditions for Clearing the DTC
The condition for setting the DTC is no longer present.
Reference Information
Schematic Reference
HVAC Schematics HVAC - Manual
Connector End View Reference
Component Connector End Views Sunshade - Left (DH6)
Description and Operation
Manual HVAC Description and Operation HVAC - Manual
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Testing
1. Ignition OFF, remove the KR29 A/C Compressor Clutch Relay, ignition ON.
2. 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 harness connector at the K20 Engine Control Module, ignition ON.
4. 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.
6. 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
7. Test for less than 5 ohms 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 70 X2 with LBS
* Terminal 53 X1 with LE9
* Terminal 32 X1 with LFW
• If 5 ohms or greater
Repair the open/high resistance in the circuit.
• If less than 5 ohms
8. 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
9. All OK.
Component Testing
Static Test
1. Ignition OFF, disconnect the KR29 A/C Compressor Clutch Relay.
2. Test for 60-180 ohms between the B+ terminal 85 and the control terminal 86 of the KR29 A/C Compressor Clutch Relay.
• If not within 60-180 ohms
Replace the KR29 A/C Compressor Clutch Relay.
• If within 60-180 ohms
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.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
Control Module References Control Module References for engine control module replacement, programming and setup