GM Service Manual Online
For 1990-2009 cars only

Test Description

  1. These DTCs cover the Low Speed Buss Line of GM LAN. This is the circuit that carries the A/C request signal.

  1. The A/C compressor relay output is disabled if engine coolant temperature is above 128°C (262°F). The instrument panel engine coolant indicator will indicate overheating.

Step

Action

Value(s)

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

DEFINITION: The A/C compressor clutch will not engage when an A/C request has been made and a Powertrain DTC has not been set.

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Ignition ON, engine OFF.
  2. Observe the scan tool.

Do any of the following DTCs set U2100, U2103, U2105-U2199?

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Go to Data Link References

Go to Step 3

3

  1. Start the engine.
  2. Place the blower motor switch in the maximum speed position.
  3. Place the air temperature switch in the coldest position.

Does the A/C compressor operate?

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Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 4

4

  1. Start the engine.
  2. Observe the coolant temperature indicator.

Is the engine coolant temperature indicator illuminated?

 

Go to Engine Overheating

Go to Step 5

5

  1. Turn OFF the ignition.
  2. Install the J 43600 ACR 2000.
  3. Record the ambient temperature at the vehicle.
  4. Record readings of the low and high side STATIC pressures.
  5. Compare the low and the high side pressure values with the allowable limits for the recorded ambient air temperature.

Are the low and the high side pressure values within the allowable limits for the recorded ambient air temperature and are the pressure values within 103 kPa (15 psi) of each other?

Above 16°C (60°F) 345 kPa (50 psi)

Above 24°C (75°F) 483 kPa (70 psi)

Above 33°C (90°F) 690 kPa (100 psi)

Go to Step 6

Go to Leak Testing

6

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool observe the A/C refrigerant pressure sensor in the engine, engine cooling data list.
  4. Compare the A/C refrigerant pressure sensor parameter on the scan tool with the ACR 2000 high side pressure value.

Is the scan tool A/C refrigerant pressure sensor parameter and the ACR 2000 pressure value within 15 psi of each other?

 

Go to Step 7

Go to Step 14

7

With a scan tool, view the ambient air temperature in the HVAC system data.

Is the ambient air temperature below 3°C (38F°)?

 

Go to Step 17

Go to Step 8

8

  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the terminal B supply voltage circuit of the A/C compressor clutch with a test lamp that is connected to ground.
  5. With a scan tool, command the A/C compressor clutch relay ON.

Does the test lamp illuminate?

--

Go to Step 9

Go to Step 10

9

Test the ground circuit of the A/C compressor clutch for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 26

Go to Step 13

10

Test the voltage supply circuit of the A/C compressor clutch for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 26

Go to Step 11

11

  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the battery positive voltage circuit on the switch side of the A/C compressor clutch relay with a test lamp that is connected to ground.

Does the test lamp illuminate?

--

Go to Step 12

Go to Step 22

12

Inspect for poor connections at the A/C compressor clutch relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 26

Go to Step 23

13

Inspect for poor connections at the harness connector of the A/C compressor clutch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 26

Go to Step 24

14

  1. Disconnect the A/C pressure sensor.
  2. With a test lamp connected to battery voltage, probe the terminal 1 low reference circuit at the A/C refrigerant pressure sensor connector.

Does the test lamp illuminate?

--

Go to Step 18

Go to Step 15

15

Test the low reference circuit of the A/C refrigerant pressure sensor for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 26

Go to Step 16

16

Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 26

Go to Step 25

17

Inspect the ambient air temperature sensor circuits for high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 26

Go to Step 20

18

Inspect for poor connections at the harness connector of the A/C refrigerant pressure sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

 

Go to Step 26

Go to Step 19

19

Replace the A/C refrigerant pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement .

Did you complete the replacement?

 

Go to Step 26

--

20

Inspect for poor connections at the harness connector of the ambient air temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 26

Go to Step 21

21

Replace the ambient air temperature sensor. Refer to Ambient Air Temperature Gage Sensor Replacement .

Did you complete the replacement?

--

Go to Step 26

--

22

Repair the battery positive voltage circuit of the A/C compressor clutch relay. Refer to Wiring Repairs .

Did you complete the repair?

--

Go to Step 26

--

23

Replace the A/C compressor clutch relay.

Refer to Relay Replacement .

Did you complete the replacement?

--

Go to Step 26

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24

Replace the A/C compressor clutch. Refer to Compressor Clutch Assembly Replacement .

Did you complete the replacement?

--

Go to Step 26

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25

Replace the HVAC control module. Refer to HVAC Module Assembly Replacement .

Did you complete the replacement?

--

Go to Step 26

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26

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2