Electric Cooling Fan Diagnosis Functional Check
Refer to Engine Cooling Schematics
Engine Cooling Fan Motor Controls
.
Circuit Description
Power for the fan motors is supplied through the cooling fan fuse in the left Maxi-fuse fuse block. The cooling fan relays are energized when current flows from the cooling fan fuse in the instrument panel (IP) fuse block through the relay coils to ground through the PCM. The cooling fan 1 control circuit is grounded for low speed fan operation. The cooling fan 1 and cooling fan 2 control circuits are grounded for high speed operation.
During low speed fan operation the PCM supplies a ground path for the low speed cooling fan relay 1. This closes the low speed relay contacts, allowing current to flow from the battery junction block through the relay contacts to the primary cooling fan. During low speed operation, the ground path for the primary cooling fan is through the series/parallel cooling fan relay and secondary cooling fan motor. The result is a series circuit with both fans running at low speed.
During high speed cooling fan operation the PCM supplies a ground path for the low speed cooling fan relay through the cooling fan 1 control circuit. The PCM also supplies a ground path for the high speed cooling fan relay 3 and the series/parallel cooling fan relay 2 through the cooling fan 2 control circuit. This closes all 3 fan relays. During high speed operation, both the left and the right cooling fans are supplied current from the battery junction block and each fan has a ground path. The PCM will also enable the cooling fans on low speed for 3 minutes after the ignition is turned off when the coolant temperature exceeds 140°C (284°F).
Diagnostic Aids
Check for the following conditions:
| • | A faulty connection at the PCM, the cooling fan relays, or the cooling fan motors |
| Inspect the harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connections. Use a corresponding mating terminal to test for the correct terminal tension. |
| • | Inspect the wiring harness for damage. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
If the owner noted an overheating problem, determine if the complaint was due to an actual boil-over, the warning indicator light illuminating, or the engine coolant temperature gauge indicating overheating. The gauge accuracy can also be checked by comparing the engine coolant temperature (ECT) sensor reading using a scan tool and comparing its reading with the gauge reading. If the engine is actually overheating, and the gauge indicated overheating but the cooling fan is not coming on, the ECT sensor has probably shifted out of calibration and should be replaced.
If the engine is overheating and the cooling fans are ON, the cooling system should be checked. Refer to Engine Overheating in Engine Cooling.
The PCM commands the fans ON or OFF at the following temperatures:
| • | Commands the low-speed fans ON at 106°C (223°F) and OFF at 102°C (216°F) |
| • | Commands the high-speed fans ON at 112°C (234°F) and OFF at 105°C (221°F) |
| • | With low coolant--Commands the low-speed fans ON at 80°C (176°F) and OFF at 76°C (169°F) |
| • | With low coolant--Commands the high-speed fans ON at 100°C (212°F) and OFF at 98°C (208°F) |
| • | When the A/C is requested--Commands the fans ON or OFF when the A/C refrigerant pressure is at the following levels: |
| - | Commands the low-speed fans ON when the pressure is more than 1372 kPa (190 psi) |
| - | Commands the low-speed fans OFF when the pressure is at 1218 kPa (177 psi) |
| - | Commands the high-speed fans ON when the pressure is at 1632 kPa (237 psi) |
| - | Commands the high-speed fans OFF when the pressure is at 1428 kPa (207 psi) |
The DIM will command the low-speed fans ON at key-off for 3 minutes if the engine coolant temperature exceeds 118°C (244°F).
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The PCM will enable the engine cooling fans when certain DTCs are set. Refer to the applicable DTC table before proceeding with this table.
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Allow the engine coolant temperature to cool to less than 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? | -- | |||
Are the cooling fans OFF? | 100°C (212°F) | Go to Table #1 in Electric Cooling Fan Diagnosis | ||
4 | With a scan tool, command the low-speed cooling fan relay ON. Are both cooling fans ON? | -- | Go to Table #2 in Electric Cooling Fan Diagnosis | |
5 | With a scan tool, command the high-speed cooling fan relay ON. Do both cooling fans switch to high-speed? | -- | Go to Table #3 in Electric Cooling Fan Diagnosis | |
6 |
Are the cooling fans ON? | -- | ||
7 | Turn ON the A/C. Are the cooling fans ON low-speed? | -- | System OK | |
8 | Does the scan tool display an A/C request as YES? | -- | Go to Diagnostic System Check in HVAC Systems or to Diagnostic System Check HVAC Systems -- Automatic | |
9 |
Important: Program the replacement PCM. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming .Did you complete the repair? | -- | System OK | -- |
Electric Cooling Fan Diagnosis Table # 1
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Cooling Fan Functional Check? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | |
2 |
Are both fans OFF? | -- | ||
3 | Disconnect the cool fan s/p relay. Are both fans OFF? | -- | ||
4 | Remove the high speed cooling fan relay. Are both fans OFF? | -- | ||
5 |
Does the test lamp illuminate? | -- | ||
6 | Probe the cool fan s/p relay switch feed terminal at the right fan connector using a test lamp that is connected to a good ground. Does the test lamp illuminate? | -- | ||
7 | Probe the cool fan s/p relay control circuit at the cool fan s/p relay connector using a test lamp that is connected to B+. Does the test lamp illuminate? | -- | ||
8 |
Is the test lamp still illuminated? | -- | ||
9 | Probe the low speed cooling fan relay control circuit at the low speed cooling fan relay connector using a test lamp that is connected to B+. Does the test lamp illuminate? | -- | ||
10 |
Is the test lamp still illuminated? | -- | ||
11 | Test the left fan feed circuit for a short to voltage and repair as necessary. Refer to Wiring Repairs in Wiring System. Did you find and correct a condition? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | |
12 | Test the right fan feed circuit for a short to voltage and repair as necessary. Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
13 | Repair the short to voltage in the cool fan s/p relay switch feed circuit. Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
14 | Replace the low speed cooling fan relay. Did you complete the replacement? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
15 | Test the high speed cooling fan relay control circuit or the low speed cooling fan relay control circuit for a short to ground and repair as necessary. Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
16 | Replace the high speed cooling fan relay. Did you complete the replacement? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
17 | Replace the cool fan s/p relay. Did you complete the replacement? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
18 |
Important:: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the replacement? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
Electric Cooling Fan Diagnosis Table # 2
Refer to Engine Cooling Schematics
Cooling Fans and Relays
.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Cooling Fan Functional Check? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | |
2 | Did either fan turn ON when the low speed cooling fan relay was commanded ON? | -- | ||
3 | With a scan tool, command the high speed cooling fan relay ON. Did the inoperative fan from step 2 turn ON? | -- | ||
4 | Disconnect the high speed cooling fan relay. Did the inoperative fan from step 2 turn OFF? | |||
5 |
Does the test lamp illuminate? | -- | ||
6 | Probe both feed circuits at the low speed cooling fan relay connector using a test lamp that is connected to a good ground. Does test lamp illuminate for both circuits? | -- | ||
7 |
Important: Leave the jumper in place for the remainder of this table. Connect a 30 amp fused jumper wire between the switch feed circuit and the right fan feed circuit at the low speed cooling fan relay connector. Do both fans turn ON? | -- | ||
8 |
Does the test lamp illuminate? | -- | ||
9 | Connect a second 30 amp fused jumper wire between the right fan harness connector terminals. Does the left fan turn ON? | -- | ||
10 |
Does the test lamp illuminate? | -- | ||
11 | Using the second jumper wire, jumper the switch feed circuit and the left fan feed circuit together at the cool fan s/p relay connector. Do both fans turn ON? | -- | ||
12 |
Does the test lamp illuminate? | -- | ||
13 |
Does the test lamp illuminate? | -- | ||
14 | Inspect for faulty connections at the PCM and harness connectors and repair as necessary. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find a problem and correct the condition? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | |
15 | Inspect the low speed cooling fan relay control circuit for an open or short to B+ and repair as necessary. Refer to Wiring Repairs in Wiring Systems. Did you find and correct a condition? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
16 |
Did you find and correct the condition? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | |
17 | Inspect the fan motor and harness connectors for faulty terminals and replace as necessary. Refer to Wiring Repairs in Wiring Systems. Did you find and correct a condition? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | |
18 | Replace the fan motor. Refer to Engine Cooling Fan Replacement in Engine Cooling. Did you complete the replacement? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
19 | Test the left fan feed circuit for an open and repair as necessary. Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
20 | Test the supply circuit to the inoperative fan for a short to ground and repair as necessary. Refer to Wiring Repairs in Wiring System. Did you find and correct a condition? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | |
21 | Replace the fan which was not operating. Refer to Engine Cooling Fan Replacement in Engine Cooling. Did you complete the replacement? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
22 | Replace the high speed cooling fan relay. Did you complete the replacement? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
23 | Test the cool fan s/p relay switch feed circuit for a short to ground and repair as necessary. Refer to Wiring Repairs in Wiring System. Did you find and correct the condition? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | |
24 |
Important: If the fuse is blown, locate and repair a short to ground on the load circuit or a shorted component. Repair the open or the grounded circuit for the circuit that did not illuminate the test lamp. Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
25 | Inspect the low speed cooling fan relay and connector for faulty terminals and replace as necessary. Refer to Wiring Repairs in Wiring System. Did you find and correct a condition? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | |
26 | Replace the low speed cooling fan relay. Did you complete the replacement? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
27 | Test the right fan feed circuit for an open and repair as necessary. Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
28 | Test the cool fan s/p relay switch feed circuit for an open and repair as necessary. Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
29 | Inspect the cool fan s/p relay and connector for faulty terminals and replace as necessary. Refer to Wiring Repairs in Wiring System. Did you find and correct a condition? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | |
30 | Replace the cool fan s/p relay. Did you complete the replacement? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
31 |
Important: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the replacement? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
Electric Cooling Fan Diagnosis Table # 3
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Cooling Fan Functional Check? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | |
2 |
Did both fans operate with no change? | -- | ||
3 | Did the right fan stop operating? | -- | ||
4 |
Does the test lamp illuminate after a few seconds? | -- | ||
5 | Probe the coil feed circuit at the high speed cooling fan relay connector using a test lamp that is connected to a good ground. Does the test lamp illuminate? | -- | ||
6 | Probe the switch feed circuit at the high speed cooling fan relay connector using a test lamp that is connected to a good ground. Does the test lamp illuminate? | -- | ||
7 | Install a 30 amp fused jumper between the high speed cooling fan relay switch feed circuit and the left fan feed circuit at the high speed fan relay connector. Does the left fan turn ON? | -- | ||
8 |
Do the fans switch from low to high speed? | -- | ||
9 |
Does the test lamp illuminate after a few seconds? | -- | ||
10 | Probe the ground circuit at the cool fan s/p relay connector using a test lamp that is connected to B+. Does the test lamp illuminate? | -- | ||
11 | Probe the coil feed circuit at the cool fan s/p relay connector using a test lamp that is connected to a good ground. Does the test lamp illuminate? | -- | ||
12 | Repair the high speed cooling fan relay control circuit for an open between the high speed fan relay and the splice. Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
13 | Repair the open in the high speed cooling fan relay coil feed circuit . Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
14 |
Important: If the fuse is blown, locate and repair a short to ground on the load circuit or a shorted component. Repair the open in the high speed cooling fan relay switch feed circuit . Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
15 | Replace the high speed cooling fan relay. Did you complete the replacement? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
16 | Repair the open in the left fan feed circuit between the high speed cooling fan relay and the splice. Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
17 | Repair the high speed cooling fan relay control circuit for an open or for a short to B+. Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
18 | Repair the open in the high speed cooling fan relay control circuit between the cool fan s/p relay and the splice. Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
19 | Repair the open in the ground circuit. Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
20 | Replace the cool fan s/p relay. Did you complete the replacement? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
21 |
Important: If the fuse is blown, locate and repair a short to ground on the load circuit or a shorted component. Repair the open in the cool fan s/p relay coil feed circuit . Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
22 |
Did you find and correct the condition? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | |
23 |
Important:: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the replacement? | -- | Go to Functional Check in Electric Cooling Fan Diagnosis | -- |
