| Table 1: | Electric Cooling Fan Functional Check |
| Table 2: | Electric Cooling Fan Table #1 |
| Table 3: | Electric Cooling Fan Table #2 |
| Table 4: | Electric Cooling Fan Table #3 |
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 Diagnostic Trouble Codes 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.
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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.
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Allow engine coolant temperature to cool below 100°C (212°F) before proceeding with diagnosis.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Are any DTCs set? | -- | Go to applicable DTC Table | ||
Are the cooling fans OFF? | 100°C (212°F) | Go to Electric Cooling Fan Table #1 | ||
4 | With a scan tool, command the low speed cooling fan relay ON. Are both cooling fans ON? | -- | Go to Electric Cooling Fan Table #2 | |
5 | With a scan tool, command the high speed cooling fan relay ON. Do both cooling fans switch to high speed? | -- | Go to Electric Cooling Fan Table #3 | |
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 A Diagnostic System Check in HVAC for further diagnosis of the A/C system | |
9 | Does the scan tool display A/C request as YES? | -- | Go to A Diagnostic System Check in HVAC for further diagnosis of the A/C Refrigerant Pressure Sensor | Go to A Diagnostic System Check in HVAC for further diagnosis of the A/C system |
10 |
Important: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM.Is the action complete? | -- | System OK | -- |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Cooling Fan Functional Check? | -- | Go to Cooling Fan Functional Check | |
2 | Disconnect the low speed fan relay. Are both fans OFF? | -- | ||
3 | Disconnect series/parallel fan relay. Are both fans OFF? | -- | ||
4 |
Does the test light illuminate? | -- | ||
5 | 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 light illuminate? | -- | ||
6 | 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? | -- | ||
7 |
Is the test lamp still illuminated? | -- | ||
8 | Probe the low speed cooling fan relay control circuit at the low speed cooling fan relay connector using the test lamp that is connected to B+. Does the test lamp illuminate? | -- | ||
9 |
Is the test lamp still illuminated? | -- | ||
10 | Repair the RH fan feed circuit for a short to voltage. Refer to Wiring Repairs . Did you find and correct the condition? | -- | Go to Cooling Fan Functional Check | |
11 | Repair the LH fan feed circuit for a short to voltage. Refer to Wiring Repairs . Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
12 | Repair the short to voltage in the series/parallel relay switch feed circuit. Refer to Wiring Repairs . Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
13 | Replace the low speed cooling fan relay. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
14 | 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 . Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
15 | Replace the high speed cooling fan relay. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
16 |
Important:: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Cooling Fan Functional Check? | -- | Go to Cooling Fan Functional Check | |
2 | Did either fan turn ON when the low speed cooling fan relay was commanded ON? | -- | ||
3 |
Did the other fan turn OFF? | -- | ||
4 | Disconnect the high speed cooling fan relay. Did the fan 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 ground. Does test lamp illuminate for both circuits? | -- | ||
7 |
Important: Leave jumper in place for remainder of this table. Connect a fused jumper wire between the switch feed circuit and the LH 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. Is the right fan ON? | -- | ||
10 |
Does the test lamp illuminate? | -- | ||
11 | Using the second jumper wire, jumper the switch ignition feed circuit and the RH fan feed circuit together at the series/parallel relay connector. Do the fans come ON? | -- | ||
12 |
Is the left fan ON? | -- | ||
13 |
Is the test lamp ON? | -- | ||
14 | Inspect the PCM connections. Repair faulty connections as necessary. Refer to Testing for Electrical Intermittents and Connector Repairs . Did you find a problem and correct it? | -- | Go to Cooling Fan Functional Check | |
15 | Repair the low speed fan relay control circuit for an open or short to B+. Refer to Wiring Repairs . Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
16 | Inspect the fan motor ground circuit for an open or the fan motor connections and repair as necessary. Refer to Testing for Electrical Intermittents and Connector Repairs or Wiring Repairs . Did you find and correct the condition? | -- | Go to Cooling Fan Functional Check | |
17 | Replace the fan motor. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
18 | Repair the RH fan feed circuit for an open. Refer to Wiring Repairs . Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
19 | Replace the fan which was not operating. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
20 | Replace the high speed fan relay. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
21 | Repair the series/parallel fan relay switch feed circuit for a short to ground. Refer to Wiring Repairs . Did you find and correct the condition? | -- | Go to Cooling Fan Functional Check | |
22 | Repair the open or the grounded circuit for the circuit that did not light. Refer to Wiring Repairs . Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
23 | Replace the low speed fan relay. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
24 | Repair the LH fan feed circuit for an open. Refer to Wiring Repairs . Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
25 | Repair the series/parallel relay switch feed circuit for an open. Refer to Wiring Repairs . Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
26 | Replace the series/parallel fan relay. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
27 |
Important: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Cooling Fan Functional Check? | -- | Go to Cooling Fan Functional Check | |
2 |
Did both fans operate with no change? | -- | ||
3 | Did the left fan stop operating? | -- | ||
4 |
Does the test lamp illuminate after several seconds? | -- | ||
5 | Probe the coil feed circuit at the high speed fan relay connector location 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 fan relay connector using a test lamp that is connected to a good ground. Does the test lamp illuminate? | -- | ||
7 | Jumper the switch ignition feed circuit and the RH fan feed circuit together at the high speed fan relay connector. Is the right fan ON? | -- | ||
8 |
Do the fans switch from low to high speed? | -- | ||
9 |
Does the test lamp illuminate? | -- | ||
10 | Probe the ground circuit at the series/parallel fan relay connector using a test lamp that is connected to B+. Does the test lamp illuminate? | -- | ||
11 | Probe the coil feed circuit at the series /parallel relay connector using a test lamp that is connected to a good ground. Does the test lamp illuminate? | -- | ||
12 | Repair the high speed fan relay control circuit for an open between the high speed fan relay and the splice. Refer to Wiring Repairs . Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
13 | Repair the open in the high speed fan relay coil feed circuit . Refer to Wiring Repairs . Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
14 | Repair the open in the high speed fan relay switch feed circuit . Refer to Wiring Repairs . Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
15 | Replace the high speed fan relay. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
16 | Repair the open in the RH fan feed circuit between the high speed fan relay and the splice. Refer to Wiring Repairs . Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
17 | Repair the high speed fan relay control circuit for an open or for a short to B+. Refer to Wiring Repairs . Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
18 | Repair the open in the high speed fan relay control circuit between the series/parallel fan relay and the splice. Refer to Wiring Repairs . Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
19 | Repair the open in the ground circuit. Refer to Wiring Repairs . Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
20 | Replace the series/parallel fan relay. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
21 | Repair the open in series/parallel fan relay coil feed circuit . Refer to Wiring Repairs . Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
22 |
Did you find and correct the condition? | -- | Go to Cooling Fan Functional Check | |
23 |
Important:: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
