Diagnostic Instructions
DTC Descriptors
DTC P1546: Air Conditioning Compressor Feedback Circuit Low
DTC P1539: Air Conditioning Compressor Feedback Circuit High
Diagnostic Fault Information
Circuit
| Short to Ground
| Open/High Resistance
| Short to Voltage
| Signal Performance
|
A/C Compressor Clutch Feedback
| P1546
| P1546
| P1539
| --
|
Circuit/System Description
The A/C compressor clutch relay is monitored by the ECM/PCM through the A/C compressor clutch relay feedback circuit.
Conditions for Running the DTC
• | Any of the conditions for setting the DTC are met for 15 seconds. |
• | Battery voltage is between 11-18 volts. |
Conditions for Setting the DTC
The ECM/PCM detects that the A/C compressor clutch is not on after an A/C request has been made.
Action Taken When the DTC Sets
• | The ECM will not illuminate the malfunction indicator lamp (MIL) |
• | The ECM stores the Failure Records. |
• | The A/C compressor clutch is disabled. |
Conditions for Clearing the DTC
• | The history DTC will clear after 40 consecutive ignition cycles have occurred without a malfunction. |
• | The DTC will become history if the ECM no longer detects a failure. |
Reference Information
Schematic Reference
HVAC Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References
for scan tool information
Circuit/System Verification
- Ignition ON, observe the scan tool A/C Request Signal parameter while changing the mode switch from OFF to Defrost, the reading should change from No to Yes.
⇒ | If the reading does not change while switching between the commanded states, refer to A/C Request Malfunction. |
- Observe the scan tool A/C Compressor Cycling Switch parameter. The reading should be normal.
⇒ | If not the specified value, refer to Low Pressure Switch Malfunction. |
- Command the A/C relay ON and OFF with a scan tool. Observe the A/C compressor operation, the A/C compressor clutch should engage and disengage when changing between the commanded states.
⇒ | If the A/C compressor does not engage or does not disengage, refer to A/C Compressor Malfunction. |
Circuit/System Testing
A/C Request Malfunction
- Ignition OFF, disconnect the harness connector at the A/C high pressure switch.
- Ignition ON, mode set to Defrost, verify that a test lamp illuminates between the control circuit terminal B and ground.
⇒ | If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal refer to
Blower Motor Malfunction
. |
- Verify the scan tool A/C Request Signal parameter is No.
⇒ | If not the specified value, test the signal circuit terminal A for a short to voltage. If the circuit tests normal, replace the ECM/PCM. |
- Install a 3A fused jumper wire between the signal circuit terminal A and the control circuit terminal B. Verify the scan tool A/C Request Signal parameter is Yes.
⇒ | If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM/PCM. |
- If all circuits test normal, test or replace the A/C high pressure switch.
Low Pressure Switch Malfunction
- Ignition OFF, disconnect the harness connector at the A/C low pressure switch.
- Test for less than 1 ohm between the ground circuit terminal A and ground.
⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
- Verify the scan tool A/C Compressor Cycling Switch parameter is Normal.
⇒ | If not the specified value, test the signal circuit terminal B for short to ground. If the circuit tests normal, replace the ECM/PCM. |
- Install 3A fuse jumper between the signal circuit terminal B and the ground circuit terminal A. Verify the scan tool A/C Compressor Cycling Switch parameter is Low Pressure.
⇒ | If not the specified value, test the signal circuit for short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM/PCM. |
- If all circuits test normal, test or replace the A/C low pressure switch.
A/C Compressor Malfunction
- Ignition OFF, disconnect the A/C compressor clutch relay.
- Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
⇒ | If the test lamp illuminates, test the control circuit for a short to voltage. |
- Verify that a test lamp illuminates between the ignition circuit terminal 86 and ground.
⇒ | If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit breaker/fuse is open, test or replace the A/C compressor clutch relay. |
- Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.
⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
- Disconnect the harness connector at the A/C compressor clutch.
- Test for less than 1.0 ohm between the A/C compressor clutch ground circuit terminal A and ground.
⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
- Connect the harness connector at the A/C compressor clutch.
- Connect a 10A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the A/C compressor clutch is activated.
⇒ | If the A/C compressor clutch does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, replace the A/C compressor. |
- Connect a test lamp between the ignition circuit terminal 86 and the control circuit terminal 85.
- Command the A/C relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM/PCM. |
⇒ | If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM/PCM. |
- If all circuits test normal, test or replace the A/C compressor clutch relay.
Component Testing
Relay Test
- Ignition OFF, disconnect the A/C compressor clutch relay.
- Test for 60-180 ohms between terminals 85 and 86.
⇒ | If the resistance is not within the specified range, replace the relay. |
- Test for infinite resistance between the following terminals:
⇒ | If not the specified value, replace the relay. |
- Install a 30-amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87.
⇒ | If greater than the specified range, replace the relay. |
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.