Circuit Description
When the PCM detects an A/C request, the PCM activates 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 system has not requested the A/C, a DTC P1539 sets.
A short to voltage at any point in the A/C status circuit, or if the A/C relay contacts become stuck sets a DTC P1539.
Conditions for Running the DTC
The A/C clutch is not enabled
Conditions for Setting the DTC
A voltage is detected on the A/C status circuit for more than 15 seconds after the PCM has disengaged the A/C clutch relay.
Action Taken When the DTC Sets
| • | The PCM stores the DTC information into memory when the diagnostic runs and fails. |
| • | The Malfunction Indicator Lamp (MIL) will not illuminate. |
| • | The PCM disables the A/C. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | A last test failed, or the current DTC, clears when the diagnostic runs and does not fail. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if failures are not reported by this or any other emission related diagnostic. |
| • | Use a scan tool in order to clear the MIL/DTC. |
Diagnostic Aids
Important:
• Remove any debris from the PCM\TAC module connector surfaces before
servicing the PCM\TAC module. Inspect the PCM\TAC module connector gaskets
when diagnosing/replacing the modules. Ensure that the gaskets are installed
correctly. The gaskets prevent contaminate intrusion into the PCM\TAC
modules. • For any test that requires probing the PCM or a component
harness connector, use the Connector Test Adapter Kit J 35616
. Using this kit prevents damage
to the harness/component terminals. Refer to
Using Connector Test Adapters
in Wiring Systems. • 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 an intermittent condition, refer to
Symptoms
.
A/C Clutch Relay Underhood Electrical Center Terminal Identification | |||
|---|---|---|---|
Front of Vehicle | |||
Left Side of Vehicle | Ignition | Load | Right Side of Vehicle |
Ignition | Control | ||
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
If the PCM detects a voltage on the A/C status circuit with the A/C OFF the scan tool indicates the A/C status as ON.
-
If the scan tool displayed YES in the RAN column and INT in the FAIL column, this indicates an intermittent condition is present. Inspect the A/C status circuit for an intermittent short to B+. Refer to Symptoms . Using the Freeze Frame and/or the Failure Records data aids in locating an intermittent condition. If you can not duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data determines how many miles since the DTC set. The Fail Counter and the Pass Counter can also be used to determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that the PCM recorded. This isolates when the DTC failed.
-
The relay is shorted internally if the scan tool indicates that the test passed.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Important: Diagnose DTC P0645 first if it is set. Does the scan tool indicate the A/C Status is ON? | -- | |||
Does the scan tool indicate that this diagnostic failed this ignition? | -- | Go to Diagnostic Aids | ||
Does the scan tool indicate that DTC P1539 failed this ignition? | -- | |||
5 | Repair the short to B+ on the A/C clutch status circuit. Is the action complete? | -- | -- | |
6 | Replace the faulty A/C clutch relay. Is the action complete? | -- | -- | |
7 |
Does the scan tool indicate that this test failed? | -- | ||
8 | Select the Capture Info option and the Review Info option using the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK |
