Schematic Reference: HVAC Schematics

Did you review the Air Delivery Description and Operation and the Air Temperature Description and Operation and perform the necessary inspections?

Go to Step 2

Go to Symptoms - HVAC Systems - Manual

1. Connect a scan tool.
2. Turn the blower switch to any position except OFF.
3. Press the A/C switch to the ON position.
4. Use the scan tool to command the A/C compressor clutch (MG) relay ON. When the MG relay is energized the cooling fans will also run at low speed.

Does the A/C compressor clutch engage?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

1. Exchange the A/C MG relay with a known good relay (the fan 1, the fan 3 or the horn relay).
2. Turn the blower switch to any position except OFF.
3. Press the A/C switch to the ON position.
4. Use the scan tool to command the A/C compressor clutch (MG) relay ON.

Does the A/C compressor clutch engage?

Go to Step 15

Go to Step 4

1. Disconnect the A/C compressor clutch connector.
2. Connect a test lamp across the connector.
3. Press the A/C switch to the ON position.
4. Turn the blower switch to any position except OFF.
5. Use the scan tool to command the A/C compressor clutch (MG) relay ON.

Does the test lamp illuminate?

Go to Step 16

Go to Step 5

Test the A/C compressor clutch ground circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 6

Test the A/C compressor clutch supply voltage circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 7

1. Remove the A/C MG relay from fuse and relay block 2.
2. Start the engine and turn the blower switch to any position except OFF.
3. Test for supply voltage to the A/C MG relay at cavities 1 and 5. Refer to Power and Grounding Component Views , Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 8

Test the A/C MG relay control circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 9

Test the A/C compressor control module supply voltage circuit (including the A/C switch) for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Refer to Heater and Air Conditioning Control Replacement for A/C switch replacement.

Did you find and correct the condition?

Go to Step 21

Go to Step 10

Test the A/C compressor control module ground circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 11

Test the A/C refrigerant pressure switch circuit and the switch for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems and Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement .

Did you find and correct the condition?

Go to Step 21

Go to Step 12

Test for a short to ground in the BLU/WHT wire between the underhood data link connector terminal 8 (TE 1) and the PCM connector 2 terminal 15. Grounding this circuit puts the vehicle in diagnostic request mode and will prevent the A/C from operating when the engine speed is below 1200 RPM.

Did you find and correct the condition?

Go to Step 21

Go to Step 13

Test the A/C output control circuit for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 14

Test the A/C cutout signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 17

Inspect for a poor connection at the fuse and relay block 2 connector of the A/C MG relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 18

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

Did you find and correct the condition?

Go to Step 21

Go to Step 19

Inspect for a poor connection at the harness connector of the A/C compressor control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 20

Replace the MG relay. Refer to Compressor Relay Replacement .

Did you complete the replacement?

Go to Step 21

--

Replace the A/C compressor clutch. Refer to Compressor Clutch Plate and Hub Assembly Removal , Air Conditioning Clutch Coil Removal , Air Conditioning Clutch Coil Installation and Compressor Clutch Plate/Hub Assembly Install .

Did you complete the replacement?

Go to Step 21

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Replace the A/C compressor control module. Refer to Air Conditioning (A/C) Compressor Control Module Replacement .

Did you complete the replacement?

Go to Step 21

--

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3

1-YEL/BLU

Refrigerant Pressure Switch

B+

Ignition switch ON

2

Not Used

3-RED/BLU

A/C Cutout Signal (WOT)

0-1 Volts

Ignition Switch ON, A/C Switch OFF

10-14 Volts

Engine Running, A/C Operating

4-WHT/BLU

Ground

0-1 Volts

Ignition switch ON

5-YEL

Ignition Positive Voltage

B+

Ignition Switch ON, A/C Switch ON or Defrost Switch ON

6-7

Not Used

8-YEL/RED

A/C ON Output Control

10-14 Volts

Ignition Switch ON, A/C Switch OFF

0-1 Volts

Engine Running, A/C Operating

9-BLU/BLK

A/C MG Relay Control

B+

Ignition Switch ON, A/C Switch OFF

0-1.5 Volts

Engine Running, A/C Operating

10

Not Used