Part 1 of 2

Chart C-10 Part 1 Of 2:

A/C Refrigerant Pressure Sensor & Compressor Wiring Schematic:

Relay Center:

CIRCUIT DESCRIPTION
The A/C compressor clutch control relay is energized when the A/C is requested the Powertrain Control Module (PCM) provides a round path through CKT 459. A/C compressor clutch is delayed about 0.3 seconds after A/C is requested. This will allow the Idle Air Control (IAC) valve to adjust engine RPM for the additional load.

The PCM will disable the A/C compressor clutch control relay for any of the following reasons:

^ Engine not running.
^ A/C refrigerant pressure is about 457 psi or greater.
^ Diagnostic Trouble Code (DTC) P1530 is set, and fault is current.
^ A/C refrigerant pressure is about 17 psi or less.
^ Engine coolant temperature is about 124°C (255 °F) or greater.

If the PCM temporarily disabled the A/C compressor clutch, the clutch will be energized as follows:

^ Coolant temperature drops below 119°C (246°F).
^ A/C refrigerant pressure rises above 47 psi.
^ A/C refrigerant pressure drops below about 199 psi.
^ DTC(s) are cleared from current status.

CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. The PCM will only energize the A/C relay when the engine is running. This test will determine if the relay or CKT 459 is faulty.
2. Determines if the signal is reaching the PCM through CKT 66 from the A/C control panel. Signal should only be present when an A/C mode or defrost mode has been selected.

DIAGNOSTIC AIDS
Be sure to consider branch circuits and splices to other components. If complaint is insufficient cooling, the problem may be caused by an inoperative cooling fan. Refer to CHART C-12 for cooling fan diagnosis. Chart C-12 Coolant Fan Control Circuit

If fan operates correctly, refer to A/C diagnosis. A/C pressure outside of a range of 17 to 457 psi will cause the compressor clutch to be disabled by the PCM. Observe Tech 1 A/C refrigerant pressure for 2 minutes with engine idling and A/C "ON." If pressure goes out of range, measure pressures and diagnose. Tech 1 pressure should be within 20 psi of actual. If not, check for a circuit problem using Diagnostic Trouble Code (DTC) P1530 chart. P1530
If OK, replace the A/C refrigerant pressure sensor.