Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptor
DTC P0645 00: Air Conditioning (A/C) Clutch Relay Control CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
A/C Compressor Clutch Relay Coil Ignition | P0645 00 | P0645 00 | -- | -- |
A/C Compressor Clutch Relay Coil Control | P0645 00 | P0645 00 | P0645 00 | 1 |
1. A/C Compressor Malfunction | ||||
Circuit/System Description
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.
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
The ECM detects a short to voltage, short to ground or an open at the A/C compressor clutch relay control circuit.
Action Taken When the DTC Sets
The A/C compressor is inoperative or always active.
Conditions for Clearing the DTC
The condition for setting the DTC is no longer present.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Automatic HVAC Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the KR29 A/C Compressor Clutch Relay and the X2 harness connector at the K20 Engine Control Module (ECM).
- Ignition ON, test for greater than 11 V between the ignition circuit terminal 85 at the KR29 A/C Compressor Clutch Relay and ground.
- Test for less than 0.3 V between the control circuit terminal 86 at the KR29 A/C Compressor Clutch Relay and ground.
- Ignition OFF, test for infinite resistance between the control circuit terminal 86 at the KR29 A/C Compressor Clutch Relay and ground.
- Test for less than 5 Ω between the KR29 A/C Compressor Clutch Relay control circuit terminal 86 and the control circuit terminal 30 (X1) at the K20 Engine Control Module (ECM) harness connector.
- If all circuits test normal, test or replace the KR29 A/C Compressor Clutch Relay and verify the DTC does not reset.
| ⇒ | If less than the specified range, test the ignition circuit for a short to ground or an open/high resistance. |
| ⇒ | If greater than the specified range, test the control circuit for a short to voltage. |
| ⇒ | If less than the specified range, test the control circuit for a short to ground. |
| ⇒ | If greater than the specified value, test the control circuit for an open/high resistance. |
| ⇒ | If the DTC resets, replace the K20 Engine Control Module (ECM). |
Component Testing
Static Test
- Ignition OFF, disconnect the KR29 A/C Compressor Clutch Relay.
- Test for 60-180 Ω between the B+ terminal 85 and the control terminal 86 of the KR29 A/C Compressor Clutch Relay.
- Test for the resistance between the following terminals:
| ⇒ | If not within the specified range, replace the KR29 A/C Compressor Clutch Relay. |
| • | 30 and 86 |
| • | 30 and 87 |
| • | 30 and 85 |
| • | 85 and 87 |
| ⇒ | If not the specified value, replace the KR29 A/C Compressor Clutch Relay. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for engine control module (ECM) replacement, setup, and programming
