DTC P0645, P0646, or P0647
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DTC P0645, P0646, or P0647
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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
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Diagnostic Fault Information
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Circuit
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Short to Ground
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Open/High Resistance
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Short to Voltage
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Signal Performance
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A/C Compressor Clutch Relay Coil Ignition
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P0646
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P0645, P0646
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-
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-
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A/C Compressor Clutch Relay Coil Control
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P0646
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P0645, P0646
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P0647
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1
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1. A/C Compressor Malfunction
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Circuit/System Description
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When the A/C switch is pressed, the HVAC control module sends an A/C request signal to the engine control module (ECM) via the CAN bus. The ECM therefore grounds the A/C compressor clutch relay control circuit, which activates the clutch relay. Battery voltage is supplied via the relay contacts to the A/C compressor clutch which is then activated.
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Conditions for Running the DTC
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•
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The HVAC control module is ON.
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•
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The A/C switch is active.
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Conditions for Setting the DTC
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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.
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Action Taken When the DTC Sets
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P0645 or P0646
The A/C compressor is inoperative or always active.
P0647
The A/C compressor is inoperative.
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Conditions for Clearing the DTC
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The condition for setting the DTC is no longer present.
Schematic Reference
HVAC Schematics
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
or scan tool information
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1.
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Ignition OFF, remove the KR29 A/C Compressor Clutch Relay.
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2.
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Ignition ON, test for greater than 11 V between the ignition circuit terminal 86 at the KR29 A/C Compressor Clutch Relay and ground.
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3.
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If less than the specified range, replace the X50A Fuse Block - Underhood.
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4.
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Ignition OFF, disconnect the X1 harness connector at the K20 Engine Control Module.
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5.
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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.
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6.
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If greater than the specified range, test the control circuit for a short to voltage. If the circuit test normal, replace the X50A Fuse Block - Underhood.
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7.
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Ignition OFF, test for infinite resistance between the control circuit terminal 85 at the KR29 A/C Compressor Clutch Relay and ground.
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8.
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If less than the specified range, test the control circuit for a short to ground. If the circuit test normal, replace the X50A Fuse Block - Underhood.
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9.
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Test for less than 5 Ω between the KR29 A/C Compressor Clutch Relay control circuit terminal 85 and the control circuit terminal 11 X1 at the K20 Engine Control Module harness connector.
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10.
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If greater than the specified value, test the control circuit for an open/high resistance. If the circuit test normal, replace the X50A Fuse Block - Underhood.
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11.
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If all circuits test normal, test or replace the KR29 A/C Compressor Clutch Relay and verify the DTC does not reset.
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12.
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If the DTC resets, replace the K20 Engine Control Module.
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Static Test
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1.
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Ignition OFF, disconnect the KR29 A/C Compressor Clutch Relay.
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2.
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Test for 60-180 Ω between the B+ terminal 85 and the control terminal 86 of the KR29 A/C Compressor Clutch Relay.
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3.
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If not within the specified range, replace the KR29 A/C Compressor Clutch Relay.
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4.
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Test for the resistance between the following terminals:
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5.
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If not the specified value, replace the KR29 A/C Compressor Clutch Relay.
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Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
