Electric Cooling Fan Diagnosis Functional Check
Refer to
Cooling Fans and Relays
for a wiring diagram.
Circuit Description
The cooling fans are controlled by the PCM based on various inputs. Ignition voltage is supplied to all 3 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 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 poor 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 poor terminal to wire connection. Use a corresponding mating terminal to test for proper terminal tension. |
| • | A damaged harness. |
| Inspect the wiring harness for damage. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
If the owner complained of an overheating problem, determine if the complaint was due to an actual boil over, 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 the 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 .
The PCM will command the low speed fans ON at 106°C (223°F) and OFF at 102°C (216°F), and the high speed fans ON at 112°C (234°F) and OFF at 105°C (221°F). With low coolant, the PCM will command the low speed fans ON at 80°C (176°F) and OFF at 76°C (169°F) , and the high speed fans ON at 100°C (212°F) and OFF at 98°C (208°F). With low coolant, the PCM will command the low speed fans ON at 80°C (176°F) and OFF at 76°C (169°F), and the high speed fans ON at 100°C (212°F) and OFF at 98°C (208°F). When the A/C is requested, the PCM will command low speed fans ON when the A/C refrigerant pressure is more than 1372 Kpa (190 psi) and OFF at 1218 Kpa (177 psi), and the high speed fans ON at 1632 Kpa (237 psi) and OFF at 1428 Kpa (207 psi). Further, the DIM will command the low speed fans ON at key-off for 3 minutes if the coolant temperature exceeds 118°C (244°F).
Test Description
The numbers below refer to numbers on the diagnostic table.
-
The PCM will enable the engine cooling fans when certain diagnostic trouble codes are set. Go to applicable DTC Table first before proceeding with this table.
-
Allow the engine coolant temperature to cool to less than 100°C (212°F) before proceeding with the diagnosis.
Step | Action | Value(s) | 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 low speed? | -- | System OK | |
8 | Does the scan tool display the A/C request as YES? | -- | Go to Diagnostic System Check or to Diagnostic System Check for further diagnosis of the A/C system | |
9 |
Important: The replacement PCM must be programmed. 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 |
Important: The cooling fan 1 relay and cooling fan 2 relay are improperly identified in the underhood fuse block. Refer to Cooling Fan Schematics for proper identification.
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 Electric Cooling Fan Diagnosis Functional Check | |
12 | Repair the right 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 cool fan s/p relay switch feed circuit. Refer to Wiring Repairs in Wiring System. 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 System. 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 cool fan s/p relay. Did you complete the replacement? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
18 |
Important:: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
Electric Cooling Fan Diagnosis Table # 2
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Cooling Fan Functional Check? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | |
2 |
Important: The cooling fan 1 relay and cooling fan 2 relay are improperly identified in the underhood fuse block. Refer to Cooling Fan Schematics for proper identification. 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 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 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 Electric Cooling Fan Diagnosis Functional Check | |
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 Electric Cooling Fan Diagnosis Functional Check | -- |
16 |
Did you find and correct the condition? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | |
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 Electric Cooling Fan Diagnosis Functional Check | |
18 | Replace the fan motor. Refer to Engine Cooling Fan Replacement in Engine Cooling. Did you complete the replacement? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
19 | Repair the left fan feed circuit for an open. Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
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 Electric Cooling Fan Diagnosis Functional Check | |
21 | Replace the fan which was not operating. Refer to Engine Cooling Fan Replacement in Engine Cooling. Did you complete the replacement? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
22 | Replace the high speed cooling fan relay. Did you complete the replacement? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
23 | Repair the cool fan s/p relay switch feed circuit for a short to ground. Refer to Wiring Repairs in Wiring System. Did you find and correct the condition? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | |
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 Electric Cooling Fan Diagnosis Functional Check | -- |
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 Electric Cooling Fan Diagnosis Functional Check | |
26 | Replace the low speed cooling fan relay. Did you complete the replacement? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
27 | Repair the right fan feed circuit for an open. Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
28 | Repair the cool fan s/p relay switch feed circuit for an open. Refer to Wiring Repairs in Wiring System. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
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 Electric Cooling Fan Diagnosis Functional Check | |
30 | Replace the cool fan s/p relay. Did you complete the replacement? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
31 |
Important: Program the replacement PCM. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming Did you complete the replacement? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
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 |
Important: The cooling fan 1 relay and cooling fan 2 relay are improperly identified in the underhood fuse block. Refer to Cooling Fan Schematics for proper identification.
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 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 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 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 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 cool fan 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 cool fan 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 cool fan 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:: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
