Electric Cooling Fan Diagnosis Functional Check
Refer to Engine Controls Schematics
Engine Cooling Fan Motor Controls
Circuit Description:
The cooling fans are controlled by the PCM based on various inputs. Ignition voltage is supplied to all three cooling fan relay coils. The PCM controls the low speed cooling fan relay by providing the ground path. The PCM controls the series/parallel and the high speed cooling fan relays together by providing a ground path. The left and right cooling fans are connected in series. This will enable both fans on low speed when the low speed relay is energized. When all three fan relays are energized, both fans will operate at high speed. The high speed is possible because the fan relays are wired in a parallel circuit. When the PCM detects that certain DTCs are set, the PCM will enable the cooling fans.
The PCM will enable the engine cooling fans when certain DTCs are set. The PCM will also enable the cooling fans after the ignition is turned OFF. When engine coolant temperature exceeds 140°C (284°F) and the ignition is turned OFF, the cooling fans will be enabled on low speed.
Diagnostic Aids
If the owner complained of an overheating problem, determine if the complaint was due to an actual boil over, or the warning indicator light illuminated, or the engine coolant temperature gauge indicated 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 engine coolant temperature (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 will command low speed fans ON at 108°C (226°F) and OFF at 103°C (217°F) and high speed fans ON at 113°C (235°F) and OFF at 108°C (226°F).
Test Description
The numbers below refer to numbers on the diagnostic table:
-
The PCM will enable the engine cooling fans when certain DTCs are set. Go to applicable DTC able first before proceeding with this table.
-
Allow engine coolant temperature to cool 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? | -- | |||
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. Do both cooling fans turn 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? | -- | System OK | |
8 | Does the scan tool display A/C request as YES? | -- | Go to Diagnostic System Check in HVAC for further diagnosis of the A/C system. | |
9 |
Important: Program the replacement PCM. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | System OK | -- |
Electric Cooling Fan Diagnosis TABLE 1
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Cooling Fan Functional Check? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | |
2 |
Are both fans OFF? | -- | ||
3 | Disconnect the series/parallel fan relay. Are both fans OFF? | -- | ||
4 | Remove the high speed fan relay. Are both fans OFF? | -- | ||
5 |
Does the test lamp illuminate? | -- | ||
6 | Probe the series/parallel relay switch feed terminal at the left fan connector using a test lamp that is connected to a good ground. Does the test lamp illuminate? | -- | ||
7 | Probe the series/parallel cooling fan relay control circuit at the series/parallel cooling fan 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 right fan feed circuit for a short to voltage and repair as necessary. Refer to Wiring Repairs in Wiring Systems. Did you find and correct a condition? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | |
12 | Repair the left fan feed circuit for a short to voltage. Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
13 | Repair the short to voltage in the series/parallel relay switch feed circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
14 | Replace the low speed cooling fan relay. Did you complete the replacement? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
15 | Repair the high speed cooling fan relay control circuit or the low speed cooling fan relay control circuit for a short to ground. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
16 | Replace the high speed cooling fan relay. Did you complete the replacement? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
17 | Replace the series/parallel cooling fan relay. Did you complete the replacement? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
18 |
Important:: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the replacement? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
Electric Cooling Fan Diagnosis TABLE 2
Refer to
Engine Controls Schematics
Engine Cooling Fan Motor Controls
.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Cooling Fan Functional Check? | -- | ||
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 the test lamp illuminate for both circuits? | -- | ||
7 |
Important: Leave the jumper in place for the remainder of this table. Connect a fused jumper wire between the switch feed circuit and the left 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 fused jumper wire between the left fan harness connector terminals. Does the right fan turn ON? | -- | ||
10 |
Does the test lamp illuminate? | -- | ||
11 | Using the second jumper wire, jumper the switch feed circuit and the right fan feed circuit together at the coolfan s/p relay connector. Do the fans turn ON? | -- | ||
12 |
Does the test lamp illuminate? | -- | ||
13 |
Does the test lamp illuminate? | -- | ||
14 |
Did you find a problem and correct the condition? | -- | ||
15 |
Did you find a problem and correct condition? | -- | -- | |
16 |
Did you find and correct the condition? | -- | ||
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? | -- | ||
18 | Replace the fan motor. Refer to Engine Cooling Fan Replacement in Engine Cooling. Did you complete the replacement? | -- | -- | |
19 | Inspect the right fan feed circuit for an open and repair as necessary. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |
20 | Test the supply circuit to the inoperative fan for a short to ground and repair as necessary. Refer to Wiring Repairs in Wiring Systems. Did you find and correct a condition? | -- | ||
21 | Replace the fan which was not operating. Refer to Engine Cooling Fan Replacement in Engine Cooling. Did you complete the replacement? | -- | -- | |
22 | Replace the high speed cooling fan relay. Did you complete the replacement? | -- | -- | |
23 | Repair the coolfan s/p relay switch feed circuit for a short to ground. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||
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 Systems. Did you complete the repair? | -- | -- | |
25 | Inspect the low speed cooling fan relay and connector for faulty terminals and replace as necessary. Refer to Wiring Repairs in Wiring Systems. Did you find and correct a condition? | -- | ||
26 | Replace the low speed cooling fan relay. Did you complete the replacement? | -- | -- | |
27 | Repair the left fan feed circuit for an open. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |
28 | Repair the coolfan s/p relay switch feed circuit for an open. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |
29 | Inspect the coolfan s/p relay and connector for faulty terminals and replace as necessary. Refer to Wiring Repairs in Wiring Systems. Did you find and correct a condition? | -- | ||
30 | Replace the coolfan s/p relay. Did you complete the replacement? | -- | -- | |
31 |
Important: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the replacement? | -- | -- |
Electric Cooling Fan Diagnosis TABLE 3
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Cooling Fan Functional Check? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | |
2 |
Did both fans operate with no change? | -- | ||
3 | Did the left 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 fused jumper between the high speed cooling fan relay switch feed circuit and the right fan feed circuit at the high speed fan relay connector. Does the right 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 coolfan 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 coolfan 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 Electric Cooling Fan Diagnosis Functional Check | -- |
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 Electric Cooling Fan Diagnosis Functional Check | -- |
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 Electric Cooling Fan Diagnosis Functional Check | -- |
15 | Replace the high speed cooling fan relay. Did you complete the replacement? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
16 | Repair the open in the right 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 Electric Cooling Fan Diagnosis Functional Check | -- |
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 Electric Cooling Fan Diagnosis Functional Check | -- |
18 | Repair the open in the high speed cooling fan relay control circuit between the coolfan s/p relay and the splice. Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
19 | Repair the open in the ground circuit. Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
20 | Replace the coolfan s/p relay. Did you complete the replacement? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
21 |
Improtant: 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 coolfan s/p relay coil feed circuit . Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
22 |
Did you find and correct the condition? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | |
23 |
Important:: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the replacement? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
