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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1377 (Engine Cooling System) >> Diagnostic Information and Procedures >> Cooling Fan Inoperative (Inoperative in High Speed)

Cooling Fan Inoperative (Inoperative in High Speed)

WARNING: This page is about a different car, the 2004 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
Reference Table

Symptom Causes
Fan motor inoperative in both speeds
  • Open or short to ground in the fan 1 relay supply voltage circuits.
  • Open or short to B+ in the fan 1 relay coil control circuit.
  • Open or short to ground in the fan motor supply voltage circuit.
  • Short to ground in the fan 2 coil supply voltage circuit.
  • Open or short to B+ in the fan motor ground circuit.
  • Short to B+ in the fan 2 coil control circuit.
Fan motor inoperative in high speed only
  • Open in the fan 2 relay supply voltage circuit.
  • Open in the fan 2 relay coil control circuit.
  • Open in the fan 2 relay high speed ground circuit.
Fan motor low speed operates at high speed
  • Short to ground in the fan motor ground circuit.
  • Short to ground in the fan resistor circuit.
Fan motor inoperative in low speed only Open or short to B+ in the fan resistor circuit.
Cooling Fan Inoperative (Inoperative in High Speed)

Step Action Yes No
Schematic Reference: Engine Cooling Schematics 
Connector End View Reference: Cooling System Connector End Views 
DEFINITION: The engine cooling fan motor is inoperative in high speed.
1 Did you review the Cooling System Description and Operation  and perform the necessary inspections? Go to Step 2  Go to Symptoms - Engine Cooling 
2 Run the engine until operating temperature is reached and the thermostat opens.
Does the cooling fan operate at high speed?
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems Go to Step 3 
3 Test the fan 2 relay coil 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 11  Go to Step 4 
4 Test the fan 2 relay coil control circuits for an open or for a short to B+. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 11  Go to Step 5 
5
  1. Remove the fan 2 relay.
  2. Install a 30 amp fused jumper between the fan motor control circuit and the high speed fan circuit (between cavities 3 and 5) of the fan 2 relay connector.
Does the cooling fan operate at high speed?
Go to Step 7  Go to Step 6 
6 Test for an open in the fan 2 relay high speed ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 11  Go to Step 8 
7 Inspect for a poor connection at the harness connector of the fan 2 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 11  Go to Step 9 
8 Inspect for a poor connection at the harness connector of the Powertrain Control Module (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 11  Go to Step 10 
9 Replace the fan 2 relay. Refer to Cooling Fan Relay Replacement .
Did you complete the replacement?
Go to Step 11  -
10 Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement in Engine Controls LNK or Powertrain Control Module (PCM) Replacement in Engine Controls LV6.
Did you complete the replacement?
Go to Step 11  -
11 Operate the system in order to verify the repair.
Did you correct the condition?
System OK Go to Step 3