Air Conditioning (A/C) Compressor Control Circuit Diagnosis. Pontiac Grand Prix 2000

For 1990-2009 cars only

Makes 🢒 Pontiac 🢒 2000 🢒 Grand Prix 🢒 Engine 🢒 Engine Controls - 3.1L (LG8) 🢒 Air Conditioning (A/C) Compressor Control Circuit Diagnosis

Refer to Engine Controls Schematic

Heater A/C Control and A/C Compressor Clutch Coil

DIC/HVAC and HVAC CTRL Fuse
DIC/HVAC and HVAC CTRL Fuse
Handling ESD Sensitive Parts Notice
Underhood Accessory Wiring Junction Block, ICM, Automatic Transaxle, Stop Lamp Switch and EBCM
G117
G117
Engine Controls Components
Powertrain Control Module Description
Coolant Fan Motor #1 and Coolant Fan Motor #2
Automatic Transaxle and Stop Lamp Switch
OBD II Symbol Description Notice
.

Circuit Description

When A/C is selected through the A/C control head a 12.0 volt signal is supplied to the A/C request input of the PCM. The A/C compressor clutch relay is controlled through the PCM. The PCM monitors the A/C refrigerant pressure. If the A/C refrigerant pressure, and engine operating conditions are within a specific calibrated acceptable ranges the PCM will enable the A/C compressor relay. This is accomplished by providing a ground path for the A/C relay coil within the PCM. When the A/C compressor relay is enabled battery voltage is supplied to the compressor clutch coil.

The PCM will enable the A/C compressor clutch whenever the engine is running and the A/C has been requested, unless any of the following conditions are met:

•	Throttle greater than 96%.

•	A/C head pressure greater than 440 psi (4.27 volts) or less than 36 psi (0.35 volt) (as determined by the A/C refrigerant pressure sensor).

•	Ignition voltage below 10.0 volts.

•	Engine speed greater than 4700 RPM for 5 seconds or 5400 RPM.

•	ECT greater than 124°C (255°F).

•	IAT less than 5°C (41°F)

Diagnostic Aids

Inspect for the following conditions:

Important: : Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.

•	Poor terminal connection.

Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Use a corresponding mating terminal to test for proper tension. Refer to Wiring Systems for diagnosis and repair.

•	Damaged harness.

Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault. Refer to Wiring Systems for diagnosis and repair.

•	Inspect the PCM and the engine grounds for clean and secure connections.

If the DTC is determined to be intermittent, reviewing the Failure Records can be useful in determining when the DTC was last set.

Test Description

The numbers below refer to numbers on the Diagnostic Table:

Important: : The A/C compressor clutch should not be engaged with the engine running if an A/C mode is not selected at the control head.

Stored Diagnostic Trouble Codes (That may not illuminate the Malfunction indicator Lamp) may disable the A/C compressor. This Diagnostic Table may lead to improper diagnosis and replacement of good parts if Diagnostic Trouble Codes are present.

The A/C compressor clutch should apply if the conditions under the Notice have been met.

Tests for an A/C request signal from the control head to the PCM.

Tests the ignition feed circuit to the A/C relay.

Determines whether the A/C relay or the circuitry is at fault.

Determines whether or not the PCM is turning the A/C relay on due to a false A/C request.

Isolates problem to the A/C control head or the PCM.

Step

Action

Values

Yes

Did you perform the Powertrain On Board Diagnostic (OBD) System Check?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Are any PCM DTCs stored?

Go to applicable DTCs

Go to Step 3

Important: : The following conditions must be met before continuing with this step:

•	Ambient air temperature must be above 5°C (41°F).

•	A/C Pressure must be above 36°C (96°F).

•	Coolant temperature must be below 121°C (250°F).

A/C selector switch off.
Turn the ignition on, engine off.
Listen for engagement of the A/C clutch.

Is the A/C Clutch engaged?

Go to Step 18

Go to Step 4

Start the engine.
Select Defrost or MAX mode on HVAC control.
Observe A/C compressor.

Is the A/C compressor clutch engaged?

Go to Diagnostic Aids

Go to Step 5

With Defrost or Max mode selected, monitor A/C Request display on the scan tool Engine data list.

Does A/C Request display Yes?

Go to Step 9

Go to Step 6

Turn the ignition off.
Disconnect the PCM.
Turn the ignition on.
With Defrost or Max mode selected, measure voltage on the A/C request circuit at the PCM harness connector.

Does the voltage measure near the specified value?

B+

Go to Step 8

Go to Step 7

Test the A/C request circuit for the following conditions:

Open.
Shorted to ground.
Poor connection at the A/C control head or A/C programmer (as applicable).

Did you find and correct the condition?

Go to Step 29

Go to Diagnostic System Check Manual

Diagnostic System Check Automatic

Inspect the A/C request circuit for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Did you find and correct the condition?

Go to Step 29

Go to Step 27

Observe A/C refrigerant pressure display on the scan tool.

Is A/C pressure indicated between the specified values?

36 - 440 psi

Go to Step 12

Go to Step 10

Connect J 39183-C R-134a Manifold gauge set.
Observe high side refrigerant pressure on the gauge.

Is high side refrigerant pressure within the specified values?

36 - 440 psi

Go to Step 11

Go to Diagnostic System Check Manual

Diagnostic System Check Automatic

Turn the ignition off.
Disconnect the A/C Pressure sensor.
Turn the ignition on.
View A/C Highside display on the scan tool Engine data list.

Does the scan tool display an A/C Highside pressure at the specified value?

0 psi

Go to Step 28

Go to Step 27

Disconnect the A/C relay electrical connector.
Probe the ignition feed circuits at the A/C relay harness connector with a test lamp to ground.

Did the test lamp illuminate?

Go to Step 13

Go to Step 23

Connect a fused jumper between the ignition feed circuit and A/C compressor clutch control circuit at the A/C relay connector.

Does the A/C compressor clutch engage?

Go to Step 14

Go to Step 15

Test for poor connections at A/C refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Did you find and correct the condition?

Go to Step 29

Go to Step 24

Disconnect the A/C compressor clutch electrical connector (leave the ignition control circuit and A/C compressor clutch control circuit jumpered at the A/C relay connector).
Connect a test lamp between A/C compressor clutch feed circuit and the compressor ground circuit.

Did the testlamp illuminate?

Go to Step 16

Go to Step 17

Test for poor connections at the A/C compressor clutch.
If a problem is found, replace faulty terminals as necessary. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Did you find and correct the condition?

Go to Step 29

Go to Step 25

Test for an open or short to ground in the A/C compressor clutch control circuit. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 29

Go to Step 26

Turn the ignition on.
Turn the A/C off.
Observe A/C Request display on the scan tool.

Does A/C Request display Yes?

Go to Step 19

Go to Step 21

Turn the ignition off.
Disconnect the PCM.
Turn the ignition on, turn the A/C off.
Using a DMM, measure voltage between the A/C request circuit at the PCM harness connector and ground.

Does the voltage measure near the specified value?

B+

Go to Step 20

Go to Step 27

Turn OFF the ignition.
Disconnect the A/C control head.
Turn the ignition on.
Test the A/C Request circuit for a short to battery positive voltage. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 29

Go to Diagnostic System Check Manual

Diagnostic System Check Automatic

Disconnect the A/C relay.
Start the vehicle and observe the A/C compressor.

Is the A/C compressor clutch engaged?

Go to Step 22

Go to Step 24

Locate and repair short to voltage in the A/C compressor clutch control circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 29

Repair open or short to ground in ignition feed circuit to the A/C compressor relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 29

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

Did you complete the repair?

Go to Step 29

Repair A/C compressor clutch. Refer to Air Conditioning Compressor Replacement .

Did you complete the repair?

Go to Step 29

Locate and repair open in A/C compressor clutch ground circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 29

Important: : The replacement PCM must be programmed.

Replace the PCM. Refer to Powertrain Control Module Replacement/Programming .

Did you complete the replacement?

Go to Step 29

Replace A/C refrigerant pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

Go to Step 29

Important: : The following conditions must be met before continuing with this step:

•	Ambient air temperature must be above 5°C (41°F).

•	A/C Pressure must be above 36°C (96°F).

•	Coolant temperature must be below 121°C (250°F).

Ignition on, engine running.
Turn A/C selector switch on.
Listen for engagement of the A/C clutch.

Is the A/C Clutch engaged?

System OK

Go to Step 3