GM Service Manual Online
For 1990-2009 cars only

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Action

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Schematic Reference: Engine Cooling Schematics , HVAC Schematics in HVAC Systems - Manual

Connector End View Reference: Cooling System Connector End Views

DEFINITION: One or both engine cooling fan motors run continuously in high or low speed.

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the Fans Low Speed ON and OFF.

Are one or both cooling fans ON?

Go to Step 3

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

3

Are both cooling fans running continuously?

Go to Step 4

Go to Step 6

4

Are both cooling fans running continuously in high speed?

Go to Step 5

Go to Step 7

5

Test the low reference circuit of the A/C refrigerant pressure sensor for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 18

Go to Step 14

6

Important: The S/P relay is located under the front bumper on the drivers side of the vehicle.

Remove the cool fan S/P relay.

Did the right cooling fan turn OFF?

Go to Step 10

Go to Step 8

7

Remove the cool fan LOW relay.

Did the cooling fans turn OFF?

Go to Step 12

Go to Step 9

8

Remove the cool fan HI relay.

Did the right cooling fan turn OFF?

Go to Step 13

Go to Step 11

9

Repair the short to voltage in the left cooling fan motor supply voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 18

--

10

Repair the short to voltage in the left cooling fan low reference circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 18

--

11

Repair the short to voltage in the right cooling fan motor supply voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 18

--

12

Inspect for poor connections at the cool fan LOW relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Repairs.

Did you find and correct the condition?

Go to Step 18

Go to Step 15

13

Inspect for poor connections at the cool fan HI relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Repairs.

Did you find and correct the condition?

Go to Step 18

Go to Step 16

14

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

Did you find and correct the condition?

Go to Step 18

Go to Step 17

15

Replace the cool fan LOW relay.

Did you complete the replacement?

Go to Step 18

--

16

Replace the cool fan HI relay.

Did you complete the replacement?

Go to Step 18

--

17

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 18

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18

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2