Part 2 of 2

Chart C-10 - A/C Clutch Control Circuit Diagnosis:

A/C Clutch Control Wiring Circuit:

Circuit Description:
The A/C clutch control relay is energized when the Powertrain Control Module (PCM) provides a ground path through CKT 459 and A/C is requested. A/C clutch is delayed about .3 second after A/C is requested. This will allow the IAC valve to adjust engine RPM for the additional load.

The PCM will temporarily disengage the A/C clutch relay for calibrated times for one or more of the following:
^ Hot engine restart.
^ Wide Open Throttle (WOT) (TP sensor over 90%).
^ Engine RPM greater than about 6000 RPM.
^ During IAC valve reset.

The A/C clutch relay will remain disengaged when DTC 66 is present, if A/C refrigerant pressure is out of range as described previously in this section, or there is no A/C request signal due to an open A/C select switch or circuit.

Chart Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. Determines if the A/C refrigerant pressure sensor is out of range causing the compressor clutch to be disengaged.
2. With the engine stopped and field service mode activated, the PCM should be grounding CKT 459, which should cause the test light to be "ON."

Diagnostic Aids: If complaint is insufficient cooling, the problem may be caused by an inoperative cooling fan. See CHART C-12 for cooling fan diagnosis. Chart C-12 Coolant Fan Control Circuit If fans operate correctly, see "A/C Diagnosis" in A/C section. A/C refrigerant pressure outside of a range of 43 to 428 psi will cause the compressor to be disabled by the PCM. Observe Tech 1 scan tool A/C refrigerant pressure for 2 minutes with engine idling and A/C "ON." If pressure goes out of range, refer to A/C section to measure and diagnose. Scan pressure should be within 20 psi of actual. If not, check for a circuit problem using DTC 66 chart or replace sensor. Powertrain Controls - ECM/PCM