Circuit Description
The A/C clutch relay is PCM controlled to delay A/C clutch engagement after the A/C is turned ON. This allows the PCM to adjust engine RPM before the A/C clutch engages. The PCM will engage the A/C clutch any time A/C has been requested unless any of the following conditions exist:
| • | High coolant temperature. |
| • | Low A/C system pressure. |
| • | High A/C system pressure. |
| • | Wide open throttle. |
| • | High engine RPM. |
When the heater and A/C control is placed in the A/C mode, a 12 volt signal is sent to the PCM. When the PCM receives this signal the PCM will ground the A/C clutch relay control circuit to energize the A/C relay. This is shown on the scan tool as A/C request YES.
When a request for A/C has been detected by the PCM, the PCM will ground the A/C clutch relay control circuit, the relay contacts will close, and current will flow through the relay to the A/C compressor clutch.
When A/C request has been detected by the PCM, the cooling fan(s) will be turned ON when A/C pressure is above a predetermined pressure.
Diagnostic Aids
Ensure no PCM DTC(s) are stored before using this table. The PCM will not activate the A/C clutch with a stored DTC.
Test Description
The numbers below refer to numbers on the diagnostic table.
-
A/C DTCs will disable the A/C system. Repair A/C DTCs before proceeding.
-
The request circuit is shorted to a voltage if the scan tool displays A/C request as YES.
-
A condition exists with the request circuit between the PCM and the HVAC Controller or the HVAC Controller is malfunctioning if the test lamp did not illuminate.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Are any A/C DTCs set? | -- | Go to applicable DTC table. | ||
Does the scan tool indicate A/C request as YES? | -- | |||
4 | Turn ON the A/C. Does the scan tool indicate A/C request as YES? | -- | System OK | |
5 |
Does the DMM display near the specified value when the A/C is enabled? | B+ | ||
6 |
Does the DMM indicate continuity? | -- | ||
7 | Probe the A/C request circuit at the PCM harness connector using the test lamp J 35616-200 connected to B+. Does the test lamp illuminate? | -- | ||
8 | Inspect the A/C request circuit for a short to voltage. Repair the circuit as necessary if a short to voltage is found. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | System OK | |
9 |
Important: Before replacing the HVAC Controller, refer to Functional Check in HVAC Manual. Replace the HVAC Controller. Refer to Control Assembly Replacement in HVAC Manual. Is the action complete? | -- | System OK | -- |
10 |
Did you find and correct the condition? | -- | System OK | |
11 | Repair the open A/C request circuit between the HVAC Controller and the PCM. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | System OK | -- |
12 | Repair the grounded A/C request circuit between the HVAC Controller and the PCM. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | System OK | -- |
13 |
Important:: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | System OK | -- |
