P1539

Diagnostic Chart:

CIRCUIT DESCRIPTION

When the PCM detects that A/C has been requested, the PCM will activate the A/C clutch relay. When the relay is activated, voltage should be present at both the A/C compressor clutch and the A/C clutch status terminal at the PCM.

If the PCM detects voltage on the A/C clutch status terminal when the A/C has not been requested a DTC P1539 will set.

A short to voltage at any point in the A/C status circuit, or the A/C relay contacts are stuck, will set a DTC P1539. For the A/C system schematic refer to A/C Controls - C60 or A/C Controls - C67 and C6a


CONDITIONS FOR SETTING THE DTC

Voltage is detected on the A/C status circuit for more than 5.0 seconds after the PCM has disengaged the A/C clutch relay.


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.

DIAGNOSTIC AIDS

^ The A/C status circuit goes to the A/C compressor clutch and to the A/C clutch relay. Inspect all circuits going to these components.

^ 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 malfunction is present. If the scan tool displays A/C status ON, indicates the PCM has detected a voltage on the A/C status circuit with the A/C OFF.

3. If the scan tool displayed YES in the RAN column and INT in the FAIL column, indicates an intermittent condition is present. Inspect A/C status circuit for an intermittent short to B+. refer to Symptoms. Testing and Inspection Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If the DTC cannot be duplicated, the information included in the Freeze Frame and/or Failure Records data can be useful in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also be used to determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that were noted. This will isolate when the DTC failed.

4. If the scan tool displays that the test passed, indicates that the relay is shored internally.