For 1990-2009 cars
Engine Controls Component Views
A/C System
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### 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 and the engine is operating, 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.

### Diagnostic Aids

Important:

• | Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.

• | For any test that requires probing the PCM or component harness connectors, use the Connector Test Adapter Kit J 35616 . Using this kit prevents any damage to the harness connector terminals. Refer to Using Connector Test Adapters in Wiring Systems.

Ensure no PCM DTCs 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.

1. A/C DTCs will disable the A/C system. Repair A/C DTCs before proceeding.

2. The request circuit is shorted to a voltage if the scan tool displays A/C request as YES.

3. A condition exists with the request circuit between the PCM and the HVAC Programmer, or the HVAC Programmer 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? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Are any A/C DTCs set? | -- | Go to applicable DTC table. | Go to Step 3
3 |

1. Install the scan tool.
2. Idle the engine with the A/C OFF.
3. Monitor the A/C request status using the scan tool.

Does the scan tool indicate A/C request as YES?

--

Go to Step 8

Go to Step 4

4 | Turn ON the A/C. Does the scan tool indicate A/C request as YES? | -- | System OK | Go to Step 5
5 |

1. Turn OFF the ignition.
2. Disconnect the PCM connector C2 located on the opposite side of the manufacturer's logo. Refer to Powertrain Control Module Replacement/Programming .
3. Turn ON the ignition leaving the engine OFF.
4. Probe the A/C request circuit at the PCM electrical harness connector using the DMM J 39200 connected to ground.
5. Turn the A/C to the ON position.

Does the DMM display near the specified value when the A/C is enabled?

B+

Go to Step 10

Go to Step 6

6 |

1. Turn OFF the ignition.
2. Disconnect the HVAC Programmer. Refer to Control Assembly Replacement in HVAC Systems-Manual.
3. Test the A/C request circuit for continuity between the HVAC Programmer and the PCM using the DMM J 39200 . Refer to Testing for Continuity in Wiring Systems.

Does the DMM indicate continuity?

--

Go to Step 7

Go to Step 11

7 | Probe the A/C request circuit at the PCM harness connector using the test lamp J 35616-200 connected to B+. Refer to Probing Electrical Connectors in Wiring Systems. Does the test lamp illuminate? | -- | Go to Step 12 | Go to Step 9
8 |

1. Inspect the A/C request circuit for a short to voltage.
2. If you find the A/C request circuit shorted repair the condition as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

System OK

Go to Step 9

9 | Important: Before replacing the HVAC Programmer, refer to Functional Check in HVAC Systems-Manual. Replace the HVAC Programmer. Refer to Control Assembly Replacement in HVAC Systems-Manual. Is the action complete? | -- | System OK | --
10 |

1. Inspect for a poor connection at the PCM. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
2. If you find a poor connection repair the terminal as necessary. Refer to Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

System OK

Go to Step 13

11 | Repair the open A/C request circuit between the HVAC Programmer 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 Programmer 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 | --