P0531

Diagnostic Chart:

CIRCUIT DESCRIPTION

The PCM can determine if the A/C clutch is engaged or not engaged through the A/C clutch status line. If the PCM has grounded the A/C relay control circuit, current can flow through the A/C relay to the A/C compressor clutch and back to the PCM on the A/C status circuit.

The PCM monitors the A/C clutch status circuit and can determine when the clutch has cycle from ON to OFF. As the A/C compressor cycles OFF, the PCM will record A/C refrigerant pressure from the A/C refrigerant pressure sensor. It the PCM does not detect an increase from the A/C refrigerant pressure sensor when the A/C clutch cycles back ON, a DTC P0531 will set. This condition can occur if the A/C refrigerant pressure sensor is fixed at one value.

CONDITIONS FOR SETTING THE DTC

The PCM does not detect an A/C refrigerant pressure change of more than 4.0 psi when the A/C clutch has been cycled OFF for 10.0 seconds, then ON for 10.0 seconds.

ACTION TAKEN WHEN THE DTC SETS

^ The DTC will be stored in the PCM memory when the diagnostic runs and fails.

^ The Malfunction Indicator Lamp (MIL) will not illuminate.

^ The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC

^ A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.

^ A last test failed (Current DTC) will clear when the diagnostic runs and does not fail.

^ PCM battery voltage is interrupted.

^ Using a scan tool.

DIAGNOSTIC AIDS

Inspect the harness going to the A/C clutch and going to the PCM for intermittent connections. While the engine is operating with the A/C enabled, move related electrical connectors and harnesses. This may aid in locating an intermittent fault. The scan tool failure records buffer feature my also help locate a fault. Drive the vehicle in the conditions that were noted from failure record data.

For intermittents, refer to Symptoms. Testing and Inspection

TEST DESCRIPTION

Number(s) below refer to step numbers on the diagnostic table.

2. Checks if the PCM is able to turn the A/C compressor ON.

3. Checks for an A/C refrigerant pressure sensor that is at a fixed value (stuck).

4. An intermittent open A/C clutch status circuit, can cause the PCM to wrongly detect the A/C clutch cycling. When the PCM falsely detects the clutch cycling ON and OFF and the clutch is remaining ON, a DTC P0531 will set since no refrigerant pressure change was detected. So before replacing the A/C refrigerant pressure sensor, inspect the A/C clutch status circuit.

5. If the scan tool indicates that the A/C clutch is ON, check connections at the compressor first.

6. If the B+ supply circuit to the A/C relay is intermittent, the PCM A/C clutch status circuit may not detect voltage when A/C is commanded ON. So inspect relay connections and operation.