A/C Refrigerant Pressure Sensor Circuit Diagnosis

Diagnostic Chart (Part 1 Of 2):

Diagnostic Chart (Part 2 Of 2):

Schematic:

CIRCUIT DESCRIPTION
The A/C system uses an A/C refrigerant pressure sensor mounted in the high side of the A/C system to monitor A/C refrigerant pressure. The PCM utilizes this information in order to disable the A/C compressor clutch when the A/C system pressure is out of range. The PCM also uses A/C refrigerant pressure sensor to enable the engine coolant fans when the A/C refrigerant pressure is high.

The PCM supplies a 5 volt reference, a signal circuit, and a ground circuit to the A/C refrigerant pressure sensor. As the A/C pressure increases or decreases, the resistance of the sensor changes and varies the amount of signal voltage detected by the PCM.

DIAGNOSTIC AIDS

IMPORTANT:
^ Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the modules. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM.
^ For any test that requires probing the PCM or a component harness connector, use the Connector Test Adapter Kit J 35616-A. Using this kit prevents damage to the harness/component terminals. Refer to Using Connector Test Adapters in Diagrams.
^ The following may cause an intermittent:
- Poor connections
Refer to Testing for Intermittent and Poor Connections in Diagrams.
- Mis-routed harness
- Rubbed through wire insulation
- Broken wire inside the insulation
^ If the test did not fail this ignition cycle, move the related electrical harnesses and the connectors while monitoring a scan tool.
^ Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can aid in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also aid determining 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 you observed. This isolates when the DTC failed.
^ For an intermittent, refer to Symptoms. Symptom Related Diagnostic Procedures

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
3. The normal A/C voltage is between 1.0 and 1.8 volts.
5. If the A/C pressure/voltage stays high after disconnecting the A/C refrigerant pressure sensor electrical connector, this indicates the signal circuit is shorted to a voltage.
7. This step tests for a good ground circuit.
8. This step verifies the integrity of the A/C refrigerant pressure sensor signal circuit.
11. If you have thoroughly inspected the 5.0 volt reference circuit (for opens, shorts to ground, PCM connections etc.) and is OK, then replace the PCM.
12. If you have thoroughly inspected the ground circuit for opens and the PCM connections are OK, then replace the PCM.