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Test Description

WARNING: This page is about a different car, the 2002 Oldsmobile Bravada, 2002 GMC Envoy XL, 2002 GMC Envoy, and 2002 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

  1. 2:  Tests that the PCM receives a cooling fan speed signal through the cooling fan speed signal circuit. If answer to question is Yes, ensure to refer to all Diagnostic Aids.
  2. 3:  Tests for the proper operation of the clutch hall effect sensor.
  3. 4:  Tests for the proper operation of the 5-volt reference circuit and of the low reference circuit of the cooling fan.
DTC P1481

Step Action Values Yes No
Schematic Reference: Engine Cooling Schematics 
Connector End View Reference:  Cooling System Connector End Views  
1 Did you perform the Engine Cooling Diagnostic System Check? - Go to Step 2  Go to Diagnostic System Check - Engine Cooling 
2 
  1. Install a scan tool.
  2. Start the engine.
  3. With the scan tool, observe the Fan Speed parameter in the PCM ENG 3 data list.
Does the scan tool indicate that the Fan Speed parameter is within the specified range?		 550-800 RPM Go to Diagnostic Aids Go to Step 3 
3 
  1. Turn OFF the ignition.
  2. Disconnect the cooling fan clutch harness connector at the shroud.
  3. Connect a jumper wire between each of the following circuits:
    • The 5-volt reference circuit
    • The cooling fan speed signal circuit
    • The low reference circuit
  4. Connect a digital multimeter (DMM) to the cooling fan speed signal circuit and ground.
  5. Turn ON the ignition with the engine OFF.
  6. Manually rotate the cooling fan.
Does the DMM voltage change?		 0-5 V Go to Step 10  Go to Step 4 
4 
  1. Disconnect the jumper wires.
  2. Measure the voltage between the 5-volt reference circuit and the low reference circuit of the cooling fan.
Is the voltage measurement near than the specified value?		 5 V Go to Step 5  Go to Step 7 
5
  1. Turn OFF the ignition.
  2. Probe the low reference circuit of the cooling fan clutch with a test lamp connected to battery positive voltage.
Does the test lamp illuminate?		 - Go to Step 6  Go to Step 9 
6 Test the 5-volt reference circuit of the cooling fan clutch for a high resistance, or for an open. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 15  Go to Step 7 
7 Test the cooling fan speed signal circuit of the cooling fan clutch for a short to ground, for a high resistance, or for an open. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 15  Go to Step 8 
8 Test the cooling fan speed signal circuit of the cooling fan clutch for a short to voltage. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 15  Go to Step 11 
9
  1. Disconnect the PCM.
  2. Test the low reference circuit of the cooling fan for a high resistance or for an open. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 15  Go to Step 12 
10
  1. Disconnect the jumper wires.
  2. Test the cooling fan speed signal circuit of the cooling fan clutch for an open. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 15  Go to Step 12 
11 Inspect for a poor connection at the harness connector of the cooling fan 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 15  Go to Step 13 
12 Inspect for poor connections at the harness connector of the PCM. 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 15  Go to Step 14 
13 Replace the cooling fan clutch. Refer to Fan Clutch Replacement .
Did you complete the replacement?		 - Go to Step 15  -
14
IMPORTANT: Program the PCM.
Replace the PCM. Refer to POWERTRAIN CONTROL MODULE .Did you complete the replacement?		 - Go to Step 15  -
15
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running in the DTC.
Does the DTC reset?		 - Go to Step 2  System OK
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