A/C Refrigerant Pressure Sensor Circuit Performance

Electrical Diagram:

CIRCUIT DESCRIPTION

The PCM cycles the A/C compressor clutch in order to optimize the performance of the A/C system. The PCM determines when to cycle the A/C compressor clutch by monitoring the A/C Refrigerant Pressure sensor.

The A/C Refrigerant Pressure sensor is also used by the PCM in order to enable the cooling fans when the A/C compressor head pressure reaches a predetermine value.

The PCM energizes the A/C compressor clutch when the engine speed is less than 5000 rpm and the A/C system is requested. If you request the A/C at engine speeds greater than 5000 RPM, the PCM will not energize the A/C compressor clutch until the engine speed decreases to less than 4895 RPM. Any one of the following conditions disables the A/C compressor clutch.

^ The throttle is commanded to Wide Open Throttle (WOT).

^ The A/C head pressure is greater than 2827 kPa (410 psi).

^ The A/C head pressure is less than 0 kPa (0 psi).

^ The ignition voltage is less than 10 volts.

^ The engine speed is greater than 5594 rpm.

^ The engine coolant temperature is greater than 125°C (257°F).

The PCM also disables the A/C compressor when curtain DTCs set.

DIAGNOSTIC AIDS

A/C Clutch Relay Underhood Electrical Center Terminal

Identification

Front of Vehicle

Left Side of Ignition Load flight Side of

Vehicle Ignition Control Vehicle

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.

For an intermittent, refer to Symptoms.

TEST DESCRIPTION

The numbers below refer to the step numbers on the diagnostic table.

2. This step checks if the PCM can turn the A/C compressor ON.

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

4. Inspect the A/C clutch status circuit before replacing the A/C refrigerant pressure sensor. Also, a low refrigerant charge in the A/C system can cause a A/C system performance condition. Refer to HVAC for recharging procedure.

5. Check the connections at the compressor first if the scan tool indicates that the A/C clutch is ON.

6. The PCM's A/C clutch status circuit may not detect voltage when the A/C is commanded ON if the B+ supply circuit to the A/C relay is intermittent. Inspect the relay connections and operation.