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Home >> GMC >> 2006 >> Sierra 1500 HD, 4WD >> Repair and Diagnosis >> Engine Mechanical >> Cooling System (Mechanical) >> Engine Cooling System (1 Of 2) >> Diagnostic Information and Procedures >> Cooling Fan Inoperative

Cooling Fan Inoperative

Cooling Fan Inoperative

Step Action Yes No
Schematic Reference: Engine Cooling Schematics 
Connector End View Reference: Cooling System Connector End Views 
DEFINITION: One or both cooling fan motors are inoperative in either high, low, or both speeds.
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.
Do the low speed engine cooling fans turn ON and OFF with each command?
Go to Step 3  Go to Step 4 
3
IMPORTANT: A 3-second delay occurs before the powertrain control module (PCM) changes the cooling fan speed.
With a scan tool, command the Fans High Speed ON and OFF.Do the high speed engine cooling fans turn ON and OFF with each command?
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems Go to Step 6 
4
    IMPORTANT: Do NOT remove the jumper wire that you will be connecting until your testing is completed. If the low speed fan fuse opens when you connect the jumper wire, repair the cooling fan motor supply voltage circuit of the right cooling fan motor for a short to ground.
  1. Disconnect the low speed fan relay.
  2. Connect a jumper wire between the battery positive voltage circuit and the cooling fan motor supply voltage circuit of the low speed fan relay.
Do both cooling fans operate in low speed?
Go to Step 14  Go to Step 5 
5
  1. Disconnect the S/P fan relay.
  2. With a test lamp connected to a good ground, probe the cooling fan low reference circuit at the S/P fan relay.
Does the test lamp illuminate?
Go to Step 9  Go to Step 8 
6 Does the right cooling fan operate at high speed? Go to Step 16  Go to Step 7 
7 Inspect the ground circuit of the S/P fan relay for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Go to Step 25  Go to Step 15 
8
  1. Install the S/P fan relay.
  2. Disconnect the right cooling fan electrical connector.
  3. With a test lamp connected to a good ground, probe the cooling fan motor supply voltage circuit at the right cooling fan motor connector.
Does the test lamp illuminate?
Go to Step 12  Go to Step 13 
9
  1. Install the S/P fan relay.
  2. Disconnect the left cooling fan motor connector.
  3. With a test lamp connected to a good ground, probe the cooling fan motor supply voltage circuit at the left cooling fan connector.
Does the test lamp illuminate?
Go to Step 11  Go to Step 10 
10 Inspect the cooling fan motor supply voltage circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 25  Go to Step 15 
11 Inspect the ground circuit of the left cooling fan for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
 
Did you find and correct the condition?
Go to Step 25  Go to Step 18 
12 Inspect the cooling fan low reference circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 25  Go to Step 17 
13 Inspect the cooling fan motor supply voltage circuit of the right cooling fan for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 25  Go to Step 19 
14 Inspect for poor connections at the low speed fan 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 25  Go to Step 20 
15 Inspect for poor connections at the S/P fan 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 25  Go to Step 21 
16 Inspect for poor connections at the high speed fan 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 25  Go to Step 22 
17 Inspect for poor connections at the harness connector of the right cooling fan. 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 25  Go to Step 23 
18 Inspect for poor connections at the harness connector of the left cooling fan. 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 25  Go to Step 24 
19 Repair the battery positive voltage circuit for an open or high resistance. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?
Go to Step 25  -
20 Replace the low speed fan relay.
Did you complete the replacement?
Go to Step 25  -
21 Replace the S/P fan relay.
Did you complete the replacement?
Go to Step 25  -
22 Replace the high speed fan relay.
Did you complete the replacement?
Go to Step 25  -
23 Replace the right cooling fan. Refer to Cooling Fan Motor Replacement - Electric .
Did you complete the replacement?
Go to Step 25  -
24 Replace the left cooling fan. Refer to Cooling Fan Motor Replacement - Electric .
Did you complete the replacement?
Go to Step 25  -
25 Operate the system in order to verify the repair.
Did you correct the condition?
System OK Go to Step 3