DTC P0645, P0646, or P0647
Diagnostic Instructions
DTC Descriptors
DTC P0645 00: Air Conditioning (A/C)
Compressor Clutch Relay Control Circuit Malfunction
DTC P0646 00: Air Conditioning (A/C)
Compressor Clutch Relay Control Circuit Low Voltage
DTC P0647 00: Air Conditioning (A/C)
Compressor Clutch Relay Control Circuit High Voltage
Diagnostic Fault Information
Circuit
|
Short to Ground
|
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 00
|
P0645 00, P0646 00
|
--
|
--
|
A/C Compressor Clutch Relay Coil Control
|
P0646 00
|
P0645 00, P0646 00
|
P0647 00
|
1
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1. A/C Compressor Malfunction
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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
• |
The HVAC control module is ON. |
• |
The A/C switch is active. |
Conditions for Setting the DTC
P0645 00 or P0646 00
The ECM detects a short to ground or an open at the A/C
compressor clutch relay control circuit.
P0647 00
The ECM detects a short to voltage at the A/C compressor clutch
relay control circuit.
Action Taken When the DTC Sets
P0645 00 or P0646 00
The A/C compressor is inoperative or always active.
P0647 00
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
Connector End View Reference
Component Connector End Views
Description and Operation
Manual HVAC Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, remove the KR29 A/C Compressor
Clutch Relay.
- 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 the specified value, test the
ignition circuit for a short to ground or an open/high
resistance. |
- Ignition OFF, disconnect the X2 harness connector at
the K20 Engine Control Module.
- 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 the specified value, test the
control circuit for a short to voltage. |
- 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 the specified value, test the control
circuit for a short to ground. |
- 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 70 X1 with LBS |
• |
Terminal 70 X1 with LSF |
⇒ |
If greater than the specified value, test the
control circuit for an open/high resistance. |
- If all circuits test normal, test or replace the
KR29 A/C Compressor Clutch Relay and verify the DTC does not
reset.
⇒ |
If the DTC resets, replace the K20 Engine
Control Module. |
Component Testing
Relay 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.
⇒ |
If not within the specified range, replace the
KR29 A/C Compressor Clutch Relay. |
- Test for the resistance between the following
terminals:
⇒ |
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 ECM replacement, setup, and
programming
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