GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2000 🢒 Seville 🢒 Engine 🢒 Engine Controls - 4.6L 🢒 Powertrain Control Module Controlled Air Conditioning (A/C) Circuit Diagnosis

Circuit Description

The PCM uses the A/C relay to control the A/C compressor. With an A/C mode selected, the Instrument Panel Module (IPM) sends a class 2 message to the dash integration module (DIM). The DIM checks to ensure that the conditions are right to allow the operation of the compressor. If the conditions are right, the DIM sends the A/C Request to the PCM via class 2 serial data. When the PCM receives the message, the PCM turns ON the A/C relay coil by grounding the A/C relay control circuit. This closes the relay contacts, and applies a fused battery voltage to the A/C compressor clutch coil. The PCM enables the compressor clutch whenever following conditions are present:

    • Engine is running.
    • The PCM has received the A/C request from the DIM.
        The DIM monitors the following components to decide whether or not to send the A/C Request:
       - A/C pressure
       - Low side pressure
       - System voltage
       - Engine coolant
    • TP sensor indicates a throttle angle below 90 percent.
    • System voltage more than 8 volts.
    • Engine speed is more than 500 RPM.

Diagnostic Aids

Check for the following conditions:

    • Faulty connections at the PCM and A/C compressor.
        Inspect the harness connectors for the following conditions:
      • Backed out terminals
      • Improperly mated terminals
      • Broken locks
      • Improperly formed or damaged terminals
      • Faulty terminal to wire connections
      • Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
    • A damaged harness.
        Inspect the wiring harnesses for damage and repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Step

Action

Values

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 the following DTCs also set?

    • DTC P0532
    • DTC P0533
    • DTC P1545
    • DTC P1639
    • U1152

--

Go to the applicable DTC first

Go to Step 3

3
  1. With the A/C OFF, start and idle the engine.
  2. Observe the A/C compressor clutch.

Is the A/C compressor clutch engage?

--

Go to Step 11

Go to Step 4

4
  1. With the engine running, select an A/C mode.
  2. Observe the A/C compressor clutch.

Is the A/C compressor clutch engaged?

--

Go to Diagnostic Aids

Go to Step 5

5

Observe the A/C Request on the scan tool.

Does the A/C Request on the scan tool indicate YES?

--

Go to Step 6

Go to Diagnostic System Check in HVAC System

6

Check the A/C Clutch fuse.

Is the A/C Clutch fuse blown?

--

Go to Step 7

Go to Step 8

7
  1. Disconnect the A/C relay.

    2. Important: Be sure to replace the A/C clutch fuse.

  2. Remove the A/C clutch fuse.
  3. Check for the following circuit conditions:
    4. • Short to ground in the circuit between the A/C clutch fuse and the A/C relay
    • A/C compressor feed shorted to chassis or the compressor ground.
  4. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a problem found?

--

Go to Step 16

Go to Air Conditioning Compressor Replacement in HVAC System

8
  1. Disconnect the A/C relay.
  2. Connect the appropriate jumper between the battery positive feed and the A/C compressor clutch feed cavities in the relay connector.

Did the A/C compressor engage?

--

Go to Step 10

Go to Step 9

9
  1. Check for the following circuit conditions:
    2. • An open circuit between the A/C fuse and the A/C relay.
    • An open A/C compressor feed circuit.
    • An open A/C compressor ground circuit.
    • Poor terminal connections at the A/C compressor.
  2. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a problem found?

--

Go to Step 16

Go to Air Conditioning Compressor Replacement in HVAC System

10
  1. Check for poor terminal connections in relay connector.
  2. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a problem found?

--

Go to Step 16

Go to Step 14

11
  1. Turn ON the ignition with the engine OFF.
  2. Observe the A/C Request on the scan tool.

Does the A/C Request indicate YES?

--

Go to Diagnostic System Check in HVAC System

Go to Step 12

12
  1. Turn OFF the ignition.
  2. Disconnect the A/C relay.
  3. Turn ON the ignition with the engine OFF.

Is the A/C compressor engaged?

--

Go to Step 13

Go to Step 14

13
  1. Check the A/C compressor feed circuit for a short to voltage.
  2. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a problem found?

--

Go to Step 16

Go to Air Conditioning Compressor Replacement in HVAC System

14

Replace the A/C relay. Refer to A/C Compressor Relay Replacement.

Is the action complete?

--

Go to Step 16

--

15
  1. With the A/C OFF, start and idle the engine.
  2. Observe the A/C compressor clutch.

Is the A/C compressor clutch engaged?

--

Go to Step 11

Go to Step 16

16
  1. Select an A/C mode.
  2. Observe the A/C compressor.

Is the A/C compressor clutch engaged?

--

System OK

Go to Step 2