Electric Cooling Fan Diagnosis Description
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 cooling fan relay # 1 by providing the ground path. The PCM controls cooling fan relays # 2 and # 3 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 fan #1 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 .
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).
Electric Cooling Fan Diagnosis Functional Check
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? | -- | |||
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 Fans ON. Are both cooling fans ON? | -- | Go to Table #2 in Electric Cooling Fan Diagnosis | |
5 | With a scan tool, command the High Speed Fans 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 indicate A/C request as YES? | -- | Go to Diagnostic System Check in HVAC. | |
9 |
Important: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM.Did you complete the repair? | -- | 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 | Disconnect fan relay #1 Are both fans OFF? | -- | ||
3 | Disconnect fan relay #3 Are both fans OFF? | -- | ||
4 |
Does the test lamp illuminate? | -- | ||
5 | Probe terminal A of the left fan connector using a test lamp that is connected to a good ground. Does the test lamp illuminate? | -- | ||
6 | Probe the cooling fan relay 2 and 3 control circuit (473) at the cooling fan relay #3 connector location (C10) using a test lamp that is connected to B+. Does the test lamp illuminate? | -- | ||
7 |
Is the test lamp still illuminated? | -- | ||
8 | Probe the cooling fan relay 1 control circuit (335) at the cooling fan relay #1 connector location (B1) 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 (504) for a short to voltage. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | |
11 | Repair the LH fan feed circuit (409) for a short to voltage. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
12 | Repair the short to voltage in the relay #3 switch feed circuit (532). Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
13 | Replace the cooling fan relay #1. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
14 | Repair the relay 2 and 3 control circuit (473) or the relay 1 control circuit (335) 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 | -- |
15 | Replace the cooling fan relay #2. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
16 |
Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the repair? | -- | 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 | Did either fan turn ON when the Low Speed Fans were commanded ON? | -- | ||||||||
3 |
Did the Left fan turn OFF? | -- | ||||||||
4 |
Does the test lamp illuminate? | -- | ||||||||
5 | Probe both feed circuits (1640 and 402) at the relay #1 connector locations (B3 and C3) using a test lamp that is connected to a good ground. Does test lamp illuminate for both circuits? | -- | ||||||||
6 |
Important: Leave jumper in place for remainder of this table. Connect a fused jumper wire between the switch feed circuit (402) and the LH fan feed circuit (409) at the relay #1 connector locations (B3 and C1). Do both fans turn ON? | -- | ||||||||
7 |
Does the test lamp illuminate? | -- | ||||||||
8 | Connect a second fused jumper wire between the fan harness connector terminals. Is the right fan ON? | -- | ||||||||
9 |
Does the test lamp illuminate? | -- | ||||||||
10 | Using the second jumper wire, jumper the switch feed circuit (532) and the RH fan feed circuit (504) together at relay #3 connector locations (B9 and C8). Do the fans come ON? | -- | ||||||||
11 |
Is the test lamp illuminated? | -- | ||||||||
12 |
Is the test lamp illuminated? | -- | ||||||||
13 | Inspect the PCM connections. Repair faulty connections as necessary. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | |||||||
14 | Repair the relay 1 control circuit (335) for an open or shorted to B+. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- | ||||||
15 | Inspect the fan motor ground circuit for a open or the fan motor connections and repair as necessary. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs or Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | |||||||
16 | Replace the fan motor. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- | ||||||
17 | Repair the RH fan feed circuit (504) for an open. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- | ||||||
18 | Replace the fan which was not operating. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- | ||||||
19 | Replace fan relay #2. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- | ||||||
20 | Repair the relay #3 switch feed circuit (532) for a short to ground. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | |||||||
21 |
Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- | ||||||
22 | Replace fan relay #1. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- | ||||||
23 | Repair the LH fan feed circuit (409) for a open. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- | ||||||
24 | Repair the relay #3 switch feed circuit (532) for a open. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- | ||||||
25 | Replace fan relay #3. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- | ||||||
26 |
Important: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the repair? | -- | 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 |
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 (1640) at relay #2 connector location (C6) using a test lamp that is connected to a good ground. Does the test lamp illuminate? | -- | ||
6 | Probe the switch feed circuit (402) at the relay #2 connector location (C4) using a test lamp that is connected to a good ground. Does the test lamp illuminate? | -- | ||
7 | Jumper the switch ignition feed circuit (402) and the RH fan feed circuit (504) together at the relay #2 connector locations (C4 and B6). 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 (150) at the relay #3 connector location (B10) using a test lamp that is connected to B+. Does the test lamp illuminate? | -- | ||
11 | Probe the coil feed circuit (1640) at the relay #3 connector location (B8) using a test lamp that is connected to a good ground. Does the test lamp illuminate? | -- | ||
12 | Repair the relay 2 and 3 control circuit (473) for an open between fan relay #2 and the splice. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
13 | Repair the open in the relay #2 coil feed circuit (1640). Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
14 | Repair the open in the relay #2 switch feed circuit (402). Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
15 | Replace the fan relay #2. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
16 | Repair the open in the RH fan feed circuit (504) between fan relay #2 and the splice. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
17 | Repair the fan 2 and 3 relay control circuit (473) for an open or for a short to B+. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
18 | Repair the open in the fan 2 and 3 relay control circuit (473) between fan relay #3 and the splice. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
19 | Repair the open in the ground circuit (150). Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
20 | Replace the fan relay #3. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
21 | Repair the open in relay #3 coil feed circuit (1640). Refer to Wiring Repairs in Wiring Systems. 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. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the repair? | -- | Go to Electric Cooling Fan Diagnosis Functional Check | -- |
