Refer to Engine Controls Schematics
Cooling Fans and Relays
.
Circuit Description
The engine cooling fan system consists of two electric cooling fans and three fan relays that are controlled by the PCM. The cooling fans receive power from a 50A MaxiFuses located in the Underhood Fuse Block Assembly. The relays are wired in a series/parallel arrangement that allows the PCM to operate both fans together at low and/or high speed.
During low speed operation, the PCM supplies a ground path for the low speed fans relay through the low speed fans control circuit. This energizes the relay coil, closes the relay contacts, and supplies current to the engine cooling fans. The ground path for the right engine cooling fan is through the series/parallel cooling fan relay and the left engine cooling fan. The result is a series circuit with both fans running at low speed.
To command high speed cooling fan operation the PCM first supplies the ground path for the low speed cooling fans relay through the low speed fans control circuit. After a few seconds delay, the PCM supplies the ground path for the high speed cooling fan relay and the series/parallel cooling fan relay through the high speed fans control circuit. During high speed operation, both engine cooling fans are supplying current through their respective MaxiFuse and each fan has its own ground path.
To determine if a non-DTC fault is present, perform the Cooling Fan Functional Check. If DTC P0480 or P0481 is set, or either DTC sets during the functional check, the DTCs must be diagnosed before proceeding with any of the symptom tables.
Important: When certain diagnostic trouble codes (DTCs) are present, the PCM may command the cooling fans to run all the time. It is important to perform the Powertrain On-Board Diagnostic (OBD) System Check prior to diagnosing the engine cooling fans.
The PCM commands low speed fans operation under the following conditions:
If the cooling fans operate when commanded off and no DTCs are set, either a cooling fan relay is stuck on or a cooling fan circuit is shorted to power.
Whenever a repair is completed repeat the Cooling Fan Functional Check. The functional check will confirm proper system operation as well as help diagnose possible multiple failures, for example: two water contaminated relays.
Operational Mode | Fans Off | Low Speed Fans | High Speed Fans |
Fan Relay #1 | De-Energized | Energized | Energized |
Fan Relay #2 | De-Energized | De-Energized | Energized |
Fan Relay #3 | De-Energized | De-Energized | Energized |
Diagnostic Aids
If the cooling fans operate when commanded off and no DTCs are set, either a cooling fan relay is stuck on or a cooling fan circuit is shorted to power.
Several circuits, or a portion of a circuit, are part of the Underhood Fuse Block Assembly. Typically if a problem is narrowed down to a circuit that is found within the Underhood Fuse Block Assembly, the entire assembly must be replaced.
If the problem is intermittent refer to Intermittent Conditions
Test Description
The numbers below refer to numbers on the diagnostic table.
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The PCM will enable the engine cooling fans when certain Diagnostic Trouble Codes are set. Refer to applicable DTC Table first before proceeding with this table.
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The engine coolant temperature must be below 100°C (212°F) before proceeding with diagnosis.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Are any DTCs set? | -- | |||
|
Important: Engine coolant temperature must remain below the specified value for all cooling fan diagnoses.
Does the scan tool display the A/C request as YES? | 100°C (212°F) | Go to Powertrain Control Module Controlled Air Conditioning (A/C) Circuit Diagnosis | ||
4 |
Are the cooling fans ON? | -- | Go to Electric Cooling Fans On At All Times in Electric Cooling Fan Diagnosis | |
5 | Command the low speed cooling fans ON with a scan tool. Are both cooling fans ON? | -- | Go to Electric Cooling Fans Inoperative Low Speed Commanded in Electric Cooling Fan Diagnosis | |
6 | Command the high speed cooling fans ON with a scan tool. Do both cooling fans switch to high speed? | -- | Go to Electric Cooling Fans Inoperative High Speed Commanded in Electric Cooling Fan Diagnosis | |
7 |
Are the cooling fans ON? | -- | Go to Electric Cooling Fans On At All Times in Electric Cooling Fan Diagnosis | |
8 | Turn ON the A/C . Are the cooling fans ON? | -- | System OK | |
9 | Does the scan tool display A/C request as YES? | -- | Go to Diagnostic System Check | Go to Powertrain Control Module Controlled Air Conditioning (A/C) Circuit Diagnosis |
Test Description
The numbers below refer to the step numbers in the diagnostic table.
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This step determines if the cooling fan relay contacts are stuck closed.
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This step determines if there is a short to voltage on circuit 504.
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Any test that requires probing a component or a component harness connector, use the Connector Test Adaptor Kit J 35616-A . Using this kit prevents damage to the harness connector terminals.
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This step determines if the cooling fan relay contacts are stuck closed.
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Cooling Fan Functional Check? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | |
Are both of the cooling fans OFF? | |||
Disconnect the cooling fan relay 2. Are both of the cooling fans OFF? | |||
Does the test lamp illuminate? | |||
Disconnect the cooling fan relay 3. Are both of the cooling fans OFF? | |||
6 | Replace the cooling fan relay 1. Is the action complete | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
7 | Repair circuit 532 for a short to B+. Refer to Wiring Repairs in Wiring Systems. Is the action complete | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
8 | Repair circuit 504 for a short to B+. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
9 | Repair circuit 409 for a short to B+. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
10 | Replace the cooling fan relay 3. Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
Test Description
The numbers below refer to the step numbers in the diagnostic table.
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This step is testing for a short to ground between the right and left cooling fans. If the right cooling fan operates at high speed with cooling fan relay 1 commanded ON, this indicates a short to ground, or a stuck relay 2.
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This step tests for a bad relay. If the cooling fans operate, replace the relay.
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This step is testing for a short to ground on the B+ supply circuit to relays 1 and 3.
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This step is testing for a bad left fan motor. If the fuse opens when the relay 1 is commanded ON, replace the left fan motor.
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This step is testing for a bad right fan motor. If the fuse opens when the relay 3 is commanded ON, replace the right fan motor.
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Cooling Fan Functional Check? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | |
2 | Inspect the cooling fan MaxiFuse. Is the fuse open? | ||
Command the low speed cooling fans ON with a scan tool. Does the right cooling fan operate at high speed? | |||
4 |
Is the test lamp illuminated? | ||
5 |
Is the test lamp illuminated? | ||
6 |
Is the test lamp illuminated? | ||
Connect a fused jumper wire between the cooling fan relay 1 switch terminals at the relay harness connector. Refer to Using Fused Jumper Wires in Wiring Systems. Do both cooling fans turn ON? | |||
8 |
Does the left cooling fan turn ON? | ||
9 |
Does the test lamp illuminate? | ||
10 | Test the continuity of circuit 504 with a DMM. Refer to Testing for Continuity in Wiring Systems. Does the DMM display continuity? | ||
11 |
Does the test lamp illuminate when the relay is commanded ON? | ||
12 | Probe the right cooling fan harness connector terminal A with a test lamp connected to B+. Is the test lamp illuminated? | ||
13 | Test the continuity of circuit 409 with a DMM. Refer to Testing for Continuity in Wiring Systems. Does the DMM display continuity? | ||
Is the test lamp illuminated? | |||
15 | Probe the cooling fan relay 1 terminal 87A at the harness connector with a test lamp to B+. Is the test lamp illuminated? | ||
16 |
Is the test lamp illuminated? | ||
Is the fuse open? | |||
Is the fuse open? | Go to Intermittent Conditions | ||
19 | Repair the open circuit between the cooling fan relay #1 and the left cooling fan motor. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
20 | Repair the open cooling fan relay B+ supply circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
21 | Repair the open circuit between the cooling fan relay 2 and the right cooling fan motor. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
22 | Repair the open circuit between the left cooling fan harness connector terminal A and the cooling fan relay 2. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
23 | Repair the short to ground between the left cooling fan motor and relay 2. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
24 | Repair the short to ground between the right cooling fan motor and relay 2. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
25 | Repair the open ground circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
26 | Repair the short to ground on the affected circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
27 |
Important: Inspect for poor connections before replacing the relay. Replace the cooling fan relay 1. Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
28 |
Important: Inspect for poor connections before replacing the relay. Replace the cooling fan relay 2. Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
29 |
Important: Inspect for poor connections before replacing the cooling fan motor. Replace the LH fan motor. Refer to Engine Cooling Fan Replacement in Engine Cooling. Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
30 |
Important: Inspect for poor connections before replacing the cooling fan motor. Replace the RH fan motor. Refer to Engine Cooling Fan Replacement in Engine Cooling. Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
Test Description
The numbers below refer to the step numbers in the diagnostic table.
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This step tests the cooling fan relay #2 control circuit.
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This step tests the cooling fan relay #3 control circuit.
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Cooling Fan Functional Check? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | |
2 |
Is the right cooling fan operating at high speed? | ||
3 | Is the left cooling fan operating at high speed? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | |
4 |
Does the test lamp illuminate? | ||
Does the test lamp illuminate? | |||
6 | Connect a fused jumper wire between the cooling fan relay 2 terminals 30 and 87. Refer to Using Fused Jumper Wires in Wiring Systems. Does the left cooling fan turn ON? | ||
7 | Probe the cooling fan relay 2 terminal 87 with a test lamp connected to B+. Does the test lamp illuminate? | ||
8 |
Does the test lamp illuminate for both terminals? | ||
Does the test lamp illuminate? | |||
10 | Jumper the cooling fan relay 3 terminals 30 and 87 with a fused jumper wire. Refer to Using Fused Jumper Wires in Wiring Systems. Does the right cooling fan turn ON? | ||
11 | Repair the cooling fan relay B+ circuit for an open. Refer to Wiring Repairs in Wiring System. Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
12 |
Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
13 | Repair the cooling fan relay control circuit for an open. Refer to Wiring Repairs in Wiring System. Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
14 | Repair circuit 409 for an open. Refer to Wiring Repairs in Wiring System. Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
15 | Repair the open ground circuit between cooling fan relay 2 and the splice. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
16 | Replace the cooling fan relay 2. Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
17 | Replace the cooling fan relay 3. Is the action complete? | Go to Cooling Fan Functional Check in Electric Cooling Fan Diagnosis | -- |
