| Table 1: | Fan Relay Operation Matrix |
| Table 2: | Cooling Fan Functional Check |
| Table 3: | Cooling Fan Symptom Table 1 |
| Table 4: | Cooling Fan Symptom Table 2 |
| Table 5: | Cooling Fan Symptom Table 3 |
| Table 6: | Cooling Fan Symptom Table 4 |
| Table 7: | Cooling Fan Symptom Table 5 |
Refer to Engine Controls Schematics
Cooling Fans
.
Circuit Description
The engine cooling fan system consists of two electric cooling fans and three fan relays that are controlled by the PCM. The cooling fans receive power from two seperate 30A Maxifuses located in the Underhood Fuse Block Assembly. The relays are wired in a series/parallel arrangement that allows the PCM to operate both fans together at low or high speed.
During low speed operation, the PCM supplies a ground path for the low speed fans relay through the low speed fans control circuit. This energizes the relay coil, closes the relay contacts, and supplies current to the engine cooling fans. The ground path for the right engine cooling fan is through the series/parallel cooling fan relay and the left engine cooling fan. The result is a series circuit with both fans running at low speed.
To command high speed cooling fan operation the PCM first supplies the ground path for the low speed cooling fans relay through the low speed fans control circuit. After a 3 second delay, the PCM supplies the ground path for the high speed cooling fan relay and the series/parallel cooling fan relay through the high speed fans control circuit. During high speed operation, both engine cooling fans are suppoies current through their respective maxifuse and each fan has its own ground path.
To determine if a non-DTC fault is present, perform the Cooling Fan Functional Check. If DTC P0480 or P0481 is set, or either DTC sets during the functional check, the DTCs must be diagnosed before proceeding with any of the symptom tables.
Important: When certain diagnostic trouble codes (DTCs) are present, the PCM may command the cooling fans to run all the time. It is important to perform the Powertrain On-Board Diagnostic System Check prior to diagnosing the engine cooling fans.
The PCM commands low speed fans operation under the following conditions:
| • | Engine coolant temperature exceeds approximately 106°C (229°F). The fans will switch from low to off when the coolant drops below 102°C (216°F). |
| • | A/C operation is requested. |
| • | After the vehicle is shut off if the coolant temperature at key-off is more than 151°C (304°F) and system voltage is more than 12 volts. The fans will stay on for approximately 3 minutes. |
The PCM commands high speed operation under the following conditions:
| • | The engine coolant temperature reaches 112°C (234°F). |
| • | A/C refrigerant pressure exceeds 240 psi. The fans will will return to low speed operation if the refrigerant pressure drops below 190 psi. |
| • | When certain DTCs set. |
If the cooling fans operate when commanded off and no DTCs are set, either a cooling fan relay is stuck on or a cooling fan circuit is shorted to power.
Whenever a repair is completed repeat the Cooling Fan Functional Check. The functional check will confirm proper system operation as well as help diagnose possible multiple failures, for example: two water contaminated relays.
Operational Mode | Fans Off | Low Speed Fans | High Speed Fans |
Fan Relay #1 | De-Energized | Energized | Energized |
Fan Relay #2 | De-Energized | De-Energized | Energized |
Fan Relay #3 | De-Energized | De-Energized | Energized |
Diagnostic Aids
If the cooling fans operate when commanded off and no DTCs are set, either a cooling fan relay is stuck on or a cooling fan circuit is shorted to power.
Several circuits (or a portion of a circuit) are part of the Underhood Fuse Block Assembly. Typically if a problem is narrowed down to a circuit that is found within the Underhood Fuse Block Assembly, the entire assembly must be replaced.
If the problem is intermittent, refer to Intermittent Conditions
Relay Terminal Identification
Use the Underhood Fuse Block details located in Engine Controls Component Views , to locate the correct cavities to probe during diagnosis. Four blade relays can be inserted two ways. The number designation on the relays displayed in the Underhood Fuse Block detail correspond directly to the cavity and NOT the numbering on the relay.
Test Description
The numbers below refer to the step numbers on the diagnostic table:
-
Checks for a short to battery voltage. A short to battery voltage will result in a drained battery. When a charger is connected to the vehicle battery, the fans should be ON.
-
Checks for a short to ingition positive voltage. The fans will run continuously with the ignition in the run position.
-
If any DTCs are present, diagnose the DTCs first.
-
Checks for proper operation of the fans. Both fans should run when low and high speed operation is commanded.
-
Checks for proper fan operation with the A/C requested. Both fans should operate.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
|
Important: Ensure that the engine coolant temperature is below the specified value.
Is either or both cooling fans operating? | 100°C (212°F) | Go to Cooling Fan Symptom Table 1 | ||
|
Important: Ensure that the engine coolant temperature is below the specified value.
Is either or both cooling fans operating? | 100°C (212°F) | Go to Cooling Fan Symptom Table 1 | ||
|
Important: Ensure that the engine coolant temperature is below the specified value.
Are any DTCs set? | 100°C (212°F) | Go to the applicable DTC | ||
Do both fans operate when low speed and high speed operation is commanded? | -- | |||
|
Important: Ensure that the ambient air temperature is more than 5°C (41°F).
Are both cooling fans operating? | -- | Go to Diagnostic Aids | ||
7 | Observe the A/C Relay display on the scan tool. Does the A/C Relay display on the scan tool indicate ON? | -- | Go to Heating, Ventilation, and Air Conditioning | |
8 | Is one or both cooling fans inoperative with low speed commanded and both fans operate normally with high speed commanded? | -- | Go to Cooling Fan Symptom Table 2 | |
9 | Are both cooling fan inoperative with low speed commanded and either cooling fan inoperative with high speed commanded? | -- | Go to Cooling Fan Symptom Table 3 | |
10 | Do both cooling fans operate normally with low speed commanded and the left cooling fan inoperative with high speed commanded? | -- | Go to Cooling Fan Symptom table 4 | |
11 | Do both cooling fans operate normally with low speed commanded and the right cooling fan inoperative with high speed commanded? | -- | Go to Cooling Fan Symptom table 5 | Go to Diagnostic Aids |
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
DEFINITION: One or both cooling fans operate continuously. | ||||||||
1 | Did you perform the Cooling Fan Functional Check? | -- | Go to Cooling Fan Functional Check | |||||
2 | Are any DTCs set? | |||||||
3 |
Important: Ensure that the engine coolant temperature is below the specified value?
Are both cooling fans operating? | 100°C (212°F) | ||||||
4 | Is the left cooling fan operating? | -- | ||||||
5 |
Important: Ensure that the engine coolant temperature is below the specified value?
Are both cooling fans operating? | 100°C (212°F) | ||||||
6 | Is the left cooling fan operating? | -- | Go to Cooling Fan Functional Check | |||||
7 |
Are both cooling fans operating? | -- | ||||||
8 |
Is the left cooling fan operating? | -- | ||||||
9 | Observe the A/C Relay display on the scan tool. Does the A/C Relay on the scan tool indicate ON? | -- | Go to A Diagnostic System Check in HVAC Systems - Automatic | |||||
10 | Locate and repair the short between ignition positive voltage and CKT 532. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- | ||||
11 |
Is the action complete? | -- | Go to Cooling Fan Functional Check | -- | ||||
12 | Locate and repair the short between battery positive voltage and CKT 532. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- | ||||
13 | Replace the engine cooling fan relay 2. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- | ||||
14 |
Is the action complete? | -- | Go to Cooling Fan Functional Check | -- | ||||
15 | Replace the engine cooling fan relay 1. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- | ||||
Step | Action | Values | Yes | No |
|---|---|---|---|---|
DEFINITION: No low speed operation of one or both fans. Normal high speed operation of both fans. | ||||
1 | Did you perform the Cooling Fan Functional Check? | -- | Go to Cooling Fan Functional Check | |
2 |
Is the right cooling fan operating? | -- | ||
3 |
Are both cooling fans operating? | -- | ||
4 |
Did you find and correct the condition? | -- | Go to Cooling Fan Functional Check | |
5 | Locate and repair the short to ground in CKT 504. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
6 | Locate and repair the open in CKT 409 between cavity 87A and the splice. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
7 | Replace engine cooling fan S/P relay. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
Step | Action | Values | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
DEFINITION: No low speed operation of both fan. No high speed operation of one cooling fan. No DTCs set. | ||||||||||||
1 | Did you perform the Cooling Fan Functional Check? | -- | Go to Cooling Fan Functional Check | |||||||||
2 |
Does the left cooling fan operate when high speed operation is commanded? | -- | ||||||||||
3 |
Are both fans ON? | -- | ||||||||||
4 |
Is the test lamp ON? | -- | ||||||||||
5 |
Are both fans ON? | -- | ||||||||||
6 |
Did you find and correct the condition? | -- | Go to Electric Cooling Fan Diagnosis | |||||||||
7 |
Did you find and correct the condition? | -- | Go to Electric Cooling Fan Diagnosis | |||||||||
8 |
Did you find and correct the condition? | -- | Go to Electric Cooling Fan Diagnosis | |||||||||
9 | Locate and repair the open battery positive voltage feed to cavity 30 of engine cooling fan relay 2. Refer to Wiring Repairs in Wiring Systems. Is the action complete?? | -- | Go to Electric Cooling Fan Diagnosis | -- | ||||||||
10 |
Did you find and correct the condition? | -- | Go to Electric Cooling Fan Diagnosis | |||||||||
11 | Replace the right cooling fan. Is the action complete? | -- | Go to Electric Cooling Fan Diagnosis | -- | ||||||||
12 | Replace the left cooling fan. Is the action complete? | -- | Go to Electric Cooling Fan Diagnosis | -- | ||||||||
13 | Replace engine cooling fan S/P relay. Is the action complete? | -- | Go to Electric Cooling Fan Diagnosis | -- | ||||||||
14 | Replace the engine cooling fan relay 2. Is the action complete? | -- | Go to Electric Cooling Fan Diagnosis | -- | ||||||||
Step | Action | Values | Yes | No |
|---|---|---|---|---|
DEFINITION: Normal low speed fans operation. No high speed operation of the left cooling fan. No DTCs set. | ||||
1 | Did you perform the Cooling Fan Functional Check? | -- | Go to Cooling Fan Functional Check | |
2 |
Is the left cooling fan operating? | -- | ||
3 |
Is the test lamp ON? | -- | ||
4 |
Did you find and correct the condition? | -- | Go to Cooling Fan Functional Check | |
5 |
Did you find and correct the condition? | -- | Go to Cooling Fan Functional Check | |
6 |
Did you find and correct the condition? | -- | Go to Cooling Fan Functional Check | |
7 | Locate and repair the open/faulty splice connection in CKT 409, between cavity 87 and the splice. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
8 | Locate and repair the open battery positive feed circuit to cavity 85 in the engine cooling fan relay 1 connector. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
9 | Replace engine cooling fan relay 1. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
DEFINITION: Normal low speed fans operation. No high speed operation of the right cooling fan. No DTCs set. | ||||
1 | Did you perform the Cooling Fan Functional Check? | -- | Go to Cooling Fan Functional Check | |
2 |
Are both fans operating? | -- | ||
3 |
Is the test lamp ON? | -- | ||
4 |
Did you find and correct the condition? | -- | Go to Cooling Fan Functional Check | |
5 |
Did you find and correct the condition? | -- | Go to Cooling Fan Functional Check | |
6 | Locate and repair the open or poor splice connection in CKT 250. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
7 | Locate and repair the open battery positive feed circuit to cavity 85 in the engine cooling fan S/P relay connector. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
8 | Replace engine cooling fan S/P relay. Is the action complete? | -- | Go to Cooling Fan Functional Check | -- |
