Electric Cooling Fan Diagnosis Functional Check
Refer to Engine Controls Schematic
Coolant Fans
Circuit Description:
The engine cooling fans receive power from two separate 30 amp maxifuses located in the Underhood Electrical Center.
During low speed operation, the PCM supplies a ground path for the Cool Fan 1 relay through the Low Speed Fans Control circuit. This energizes the relay coil, closes the Fan 1 relay contacts, and supplies current to engine cooling fan #1 motor. The ground path for engine cooling fan #1 motor is through the cool fan s/p relay 3 (Cool Fan 2 relay) and engine cooling fan #2 motor. The result is a series circuit with both fans running at low speed.
To command high speed cooling fan operation the PCM first supplies a ground path for the Cool Fan 1 relay through the Low Speed Fans control circuit. After a 3 second delay, the PCM supplies a ground path for the Cool Fan 2 (series/parallel) and Cool Fan 3 relays through the High Speed Fans Control circuit. During high speed operation, both engine cooling fan motors are supplied current through their respective maxifuse and each fan has its own ground path.
The PCM will command Low Speed Cooling Fans operation under any of the following conditions:
VIN K
| • | When A/C is requested and ambient temperature is greater than 50°C (122°F). |
| • | When engine coolant temperature exceeds 106°C (223°F). |
| • | When A/C refrigerant pressure is greater than 190 psi (2 volts). |
| • | When the ignition is off and engine coolant temperature is greater than 140°C (284°F). |
VIN 1
| • | When A/C is requested and ambient temperature is more than 40°C (104°F). |
| • | When engine coolant temperature exceeds 100°C (212°F). |
| • | When A/C refrigerant pressure is more than 190 psi (2 volts). |
| • | When the ignition is off and engine coolant temperature is more than 140°C (284°F). |
The PCM will command High Speed Cooling Fans operation under any of the following conditions:
VIN K
| • | When engine coolant temperature exceeds 110°C (230°F). |
| • | When A/C refrigerant pressure is more than 240 psi (2.5 volts). |
VIN 1
| • | When engine coolant temperature exceeds 108°C (226°F). |
| • | When A/C refrigerant pressure is more than 240 psi (2.5 volts). |
Diagnostic Aids
Inspect for the following conditions:
| • | Poor connection at the PCM, cooling fan relays, or cooling fan motors. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. |
| • | Damaged harness - Inspect the wiring harness for damage. |
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 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 other 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? | -- | ||
9 |
Important: Program the replacement PCM. Replace the PCM. Refer to Powertrain Control Module Replacement/ProgrammingDid you complete the replacement? | -- | System OK | -- |
Electric Cooling Fan Diagnosis Table #1
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Cooling Fan Functional Check? | -- | ||
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 Systems. Did you find and correct a condition? | -- | Go to the 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 Systems. Did you complete the repair? | -- | Go to the 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 Systems. Did you complete the repair? | -- | Go to the Functional Check in Electric Cooling Fan Diagnosis | -- |
14 | Replace the low speed cooling fan relay. Did you complete the replacement? | -- | Go to the 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 Systems. Did you complete the repair? | -- | Go to the Functional Check in Electric Cooling Fan Diagnosis | -- |
16 | Replace the high speed cooling fan relay. Did you complete the replacement? | -- | Go to the Functional Check in Electric Cooling Fan Diagnosis | -- |
17 | Replace the cool fan s/p relay. Did you complete the replacement? | -- | Go to the Functional Check in Electric Cooling Fan Diagnosis | -- |
18 |
Important:: Program the replacement PCM. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | Go to the Functional Check in Electric Cooling Fan Diagnosis | -- |
Electric Cooling Fan Diagnosis Table #2
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Cooling Fan Functional Check? | -- | Go to the 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 the 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 the Functional Check in Electric Cooling Fan Diagnosis | -- |
16 |
Did you find and correct the condition? | -- | Go to the 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 the Functional Check in Electric Cooling Fan Diagnosis | |
18 | Replace the fan motor. Refer to Fan Replacement in Engine Cooling. Did you complete the replacement? | -- | Go to the 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 Systems. Did you complete the repair? | -- | Go to the 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 Systems. Did you find and correct a condition? | -- | Go to the Functional Check in Electric Cooling Fan Diagnosis | |
21 | Replace the fan which was not operating. Refer to Fan Replacement in Engine Cooling. Did you complete the replacement? | -- | Go to the Functional Check in Electric Cooling Fan Diagnosis | -- |
22 | Replace the high speed cooling fan relay. Did you complete the replacement? | -- | Go to the 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 Systems. Did you find and correct the condition? | -- | Go to the 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 Systems. Did you complete the repair? | -- | Go to the 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 Systems. Did you find and correct a condition? | -- | Go to the Functional Check in Electric Cooling Fan Diagnosis | |
26 | Replace the low speed cooling fan relay. Did you complete the replacement? | -- | Go to the 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 Systems. Did you complete the repair? | -- | Go to the 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 Systems. Did you complete the repair? | -- | Go to the 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 Systems. Did you find and correct a condition? | -- | Go to the Functional Check in Electric Cooling Fan Diagnosis | |
30 | Replace the cool fan s/p relay. Did you complete the replacement? | -- | Go to the Functional Check in Electric Cooling Fan Diagnosis | -- |
31 |
Important: Program the replacement PCM. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | Go to the 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 the 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 cseries/parallel 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 Systems. Did you complete the repair? | -- | Go to the 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 Systems. Did you complete the repair? | -- | Go to the 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 Systems. Did you complete the repair? | -- | Go to the Functional Check in Electric Cooling Fan Diagnosis | -- |
15 | Replace the high speed cooling fan relay. Did you complete the replacement? | -- | Go to the 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 Systems. Did you complete the repair? | -- | Go to the 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 Systems. Did you complete the repair? | -- | Go to the 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 Systems. Did you complete the repair? | -- | Go to the Functional Check in Electric Cooling Fan Diagnosis | -- |
19 | Repair the open in the ground circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to the Functional Check in Electric Cooling Fan Diagnosis | -- |
20 | Replace the cool fan s/p relay. Did you complete the replacement? | -- | Go to the Functional Check in Electric Cooling Fan Diagnosis | -- |
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 Systems. Did you complete the repair? | -- | Go to the Functional Check in Electric Cooling Fan Diagnosis | -- |
22 |
Did you find and correct the condition? | -- | Go to the Functional Check in Electric Cooling Fan Diagnosis | |
23 |
Important:: Program the replacement PCM. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | Go to the Functional Check in Electric Cooling Fan Diagnosis | -- |
