| Table 1: | Fan Relay Operation Matrix |
| Table 2: | Cooling Fan Relay 1 |
| Table 3: | Cooling Fan Relay 2 |
| Table 4: | Cooling Fan Relay 3 |
| Table 5: | Cooling Fan System Check |
| Table 6: | Cooling Fan Symptom Table 1 |
| Table 7: | Cooling Fan Symptom Table 2 |
| Table 8: | Cooling Fan Symptom Table 3 |
| Table 9: | Cooling Fan Symptom Table 4 |
| Table 10: | Cooling Fan Symptom Table 5 |
Refer to Engine Controls Schematic
Engine Cooling Fans
.
Circuit Description
The electric cooling fan system consists of 2 electric cooling fans and 3 fan relays which are controlled by the powertrain control module (PCM). 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 grounds the control circuit for fan relay 1. The relay supplies current to the fan 1 motor. The ground path for fan 1 is through fan relay 2, through the fan 2 motor to ground. The result is a series circuit with both fans running at low speed.
To command high speed cooling fan operation the PCM first grounds the control circuit for fan relay 1. After a 3 second delay, the PCM grounds the control circuit for fan relay 2 and fan relay 3. With fan relay 2 energized, both the primary and the secondary fan have a ground path, creating a parallel circuit. This causes both fans to operate at high speed.
To determine if a fault is present perform the Cooling Fan System Check. If DTC P0480 or DTC P0481 are set, or either DTC sets during the system check, the DTCs must be diagnosed before proceeding with any of the symptom tables. Due to the complex nature of the fan circuit, various symptoms result depending upon where a fault occurs within the system.
The PCM commands the low speed fans on under the following conditions:
| • | The engine coolant temperature (ECT) exceeds approximately 106°C (229°F). The fans will switch from low to off when the coolant temperature decreases to less than 102°C (216°F). |
| • | The 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 the system voltage is more than 12 volts. The fans will stay on for approximately 3 minutes. |
The PCM switches the fans to high speed under the following conditions:
| • | The engine coolant temperature reaches 112°C (234°F). |
| • | The A/C refrigerant pressure exceeds 240 psi. The fans will return to low speed operation if the refrigerant pressure decreases to less than 190 psi. |
| • | When certain DTCs are 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 System Check. The system check will confirm the correct system operation as well as help to diagnose possible multiple failures, for example, 2 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 accessory junction block. Typically if a problem is narrowed down to a circuit that is found within the junction block, the entire junction block must be replaced.
If the problem is intermittent refer to Intermittent Conditions .
Relay Terminal Identification
Use the following relay cavity tables in order to locate the correct cavities to probe during the diagnosis. The table layout corresponds to the cavity layout in the underhood accessory junction block. Four blade relays can be inserted in 2 ways. Use the table and NOT the numbering on the relay to avoid incorrect probing.
Important: The relay 2 is different (5 blade) from relay 1 and relay 3 (4 blade). If relay 2 is incorrectly replaced by a 4 blade style relay, the system will not function properly.
Top of Junction Block | |
|---|---|
Switch Load (fan 1) | Coil Ground (PCM) |
Coil Power (fuse) | Switch Power (fuse) |
Top of Junction Block | |
|---|---|
Switch Power (from fan 1) | Coil Ground (PCM) |
-- | Switch Load (fan 2) |
Coil Power (fuse) | Switch Ground |
Top of Junction Block | |
|---|---|
Switch Power (fuse) | Coil Power (fuse) |
Coil Ground (PCM) | Switch Load (fan 2) |
Test Description
The numbers below refer to the step numbers on the Cooling Fan System Check Table.
-
The Powertrain OBD System Check must be performed first so that misdiagnosis is avoided. The PCM may be commanding the fans on due to a DTC being set, etc.
-
This verifies whether or not there is a fault on the relay control circuits of the cooling fans .
-
This step is checking to see if any A/C DTCs are set. The PCM will turn on the cooling fans when certain DTCs are set. These must be diagnosed before proceeding with the Cooling Fan System Check.
-
This step is a functional test of the system in order to determine the symptom, if any, present.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||||||||
Did either fan relay driver DTC set? | 5°C - 100°C (41°F - 212°F) | Go to the appropriate DTC tables | ||||||||
With the engine idling, turn the A/C on to maximum cooling. Have any other DTCs failed this ignition? | -- | Go to the appropriate DTC tables | ||||||||
Do both cooling fans operate as commanded? | 100°C (212°F) | System OK | ||||||||
5 | Does either cooling fan operate when all fans are commanded Off? | -- | Go to Diagnostic Aids | |||||||
6 | Does only cooling fan 1 (right) operate with Fans Low Speed commanded On, then both fans operate when Fans High Speed is commanded On? | -- | ||||||||
7 | Repair a short to ground in CKT 532. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |||||||
8 | Does neither cooling fan operate with Fans Low Speed commanded On, and then only cooling fan 2 (left) operate with Fans High Speed commanded On? | -- | ||||||||
9 | Does neither cooling fan operate with Fans Low Speed commanded On, and then only cooling fan 1 (right) operate with Fans High Speed commanded On? | -- | ||||||||
10 | Do both cooling fans operate with Fans Low Speed commanded On, and then only cooling fan 2 (left) operate with Fans High Speed commanded On? | -- | ||||||||
11 | Do both cooling fans operate with Fans Low Speed commanded On, and then only cooling fan 1 (right) operate with Fans High Speed commanded On? | -- | ||||||||
12 | Does neither cooling fan operate with Fans Low Speed commanded On, then both fans operate when Fans High Speed is commanded On? | -- | ||||||||
13 | Does neither cooling fan operate when Fans Low Speed or Fans High Speed is commanded On? | -- | Go to Diagnostic Aids | |||||||
14 | Repair the open ground circuit between G117 and the splice. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
DEFINITION: No low speed operation of either cooling fan. High speed operation of cooling fan 2 (left) only. No DTCs are set. | ||||
1 | Did you perform the Cooling Fan System Check? | -- | ||
2 |
Is the voltage near the specified value? | B+ | ||
3 | Jumper terminals A and B of the cooling fan 1 connector together. Does cooling fan 2 operate? | -- | ||
4 |
Is the voltage near the specified value? | B+ | ||
5 |
Is the voltage near the specified value? | B+ | ||
6 |
Is the voltage near the specified value? | B+ | ||
7 | Replace cooling fan 1 (right). Is the action complete? | -- | -- | |
8 | Repair the open in CKT 504 between cooling fan 1 and the fan relay 1. Is the action complete? | -- | -- | |
9 | Replace fan relay 2. Is the action complete? | -- | -- | |
10 | Repair the open in CKT 342 between fan relay 1 and the splice. Is the action complete? | -- | -- | |
11 | Replace fan relay 1. Is the action complete? | -- | -- | |
12 | Repair the open in CKT 532 between fan relay 2 and cooling fan 1. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
DEFINITION: No low speed operation of either cooling fan. High speed operation of cooling fan 1 (right) only. No DTCs are set. | ||||
1 | Did you perform the Cooling Fan System Check? | -- | ||
2 |
Does cooling fan 1 (right) operate? | -- | ||
3 |
Is the voltage near the specified value? | B+ | ||
4 | Replace cooling fan 2 (left). Is the action complete? | -- | -- | |
5 | Repair the open in the ground circuit of cooling fan 2 (left). Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
6 | Repair the open in CKT 409 between cooling fan 2 (left) and fan relay 2. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
DEFINITION: Low speed operation of both fans. High speed operation of cooling fan 2 (left) only. No DTCs are set. | ||||
1 | Did you perform the Cooling Fan System Check? | -- | ||
2 |
Is the voltage near the specified value? | B+ | ||
3 |
Is the resistance less than or equal to the specified value? | 5 ohms | ||
4 |
Do both cooling fans operate? | -- | ||
5 | Repair the open in CKT 1442 between fan relay 2 and the splice. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
6 | Repair the open in CKT 473 between fan relay 2 and the splice. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
7 | Repair the open in the ground circuit between fan relay 2 and the splice. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
8 | Replace fan relay 2. Is the action complete? | -- | -- | |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
DEFINITION: Low speed operation of both fans. High speed operation of cooling fan 1 (right) only. No DTCs are set. | ||||
1 | Did you perform the Cooling Fan System Check? | -- | ||
2 |
Is the voltage near the specified value on both circuits? | B+ | ||
3 |
Is the resistance less than or equal to the specified value? | 5 ohms | ||
4 | Jumper CKT 1442 and CKT 409 of fan relay 3 together. Does cooling fan 2 (left) operate? | -- | ||
5 | Repair the affected leg of CKT 1442 between fan relay 3 and the splice. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
6 | Repair the open in CKT 473 between fan relay 3 and the splice. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
7 | Repair the open in CKT 409 between fan relay 3 and the splice. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
8 | Replace fan relay 3. Is the action complete? | -- | -- | |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
DEFINITION: No low speed operation of either cooling fan. High speed operation of both fans. No DTCs are set. | ||||
1 | Did you perform the Cooling Fan System Check? | -- | ||
2 | Verify that fan relay 2 is the correct part. Fan relay 2 is a 5 pin relay. Four pin relays like fan relay 1 and relay 3 will plug in to the connector. However, the system will have this symptom. Was a problem found? | -- | ||
3 |
Do both fans now operate at low speed? | -- | ||
4 | Replace fan relay 2 with the correct relay. Is the action complete? | -- | -- | |
5 | Replace fan relay 2. Is the action complete? | -- | -- | |
6 | Repair CKT 409 between fan relay 2 and the splice. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
