For 1990-2009 cars

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Engine Cooling Schematics . Connector End View Reference: Component 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 .
2 |

1. Install the can tool.
2. Ignition ON, 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 engine control module (ECM) 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 . | 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 fused 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 fan relay.
2. With a test lamp connected to a good ground, probe the cooling fan low reference circuit at the low speed 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 15 | Go to Step 7
7 | Inspect the ground circuit of the Low Speed fan relay for an open or high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | System OK | Go to Step 15
8 |

1. Install the Low Speed 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 low speed 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 . Did you find and correct the condition? | System OK | 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 . Did you find and correct the condition? | System OK | Go to Step 17
12 | Inspect the cooling fan low reference circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | System OK | Go to Step 16
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 . Did you find and correct the condition? | System OK | Inspect the battery positive voltage circuit for an open or high resistance. Refer to Wiring Repairs .
14 | Inspect for poor connections at the low speed fan relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | System OK | Replace the low speed fan relay.
15 | Inspect for poor connections at the high speed fan relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . | System OK | Replace the high speed fan relay.
16 | 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 . Did you find and correct the condition? | System OK | Replace the right cooling fan. Refer to Cooling Fan and Shroud Replacement .
17 | 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 . Did you find and correct the condition? | System OK | Replace the left cooling fan. Refer to Cooling Fan and Shroud Replacement .