Table 1

Cooling Fan Symptom Table 1:

Engine Controls Schematics: 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 tan 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 tans 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 tan circuit, various symptoms result depending upon where a fault occurs within the system. Component Tests and General Diagnostics

The PCM commands the low speed tans 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 tans 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.

Fan Relay Operation Matrix:

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. Intermittent Conditions

Cooling Fan Relay 1:

Cooling Fan Relay 2:

Cooling Fan Relay 3:

RELAY TERMINAL IDENTIFICATION
Use the 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.

TEST DESCRIPTION
The numbers below refer to the step numbers on the Cooling Fan System Check Table.
1. 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.
2. This verifies whether or not there is a fault on the relay control circuits of the cooling fans.
3. This step is checking to see it any A/C DTCs are set. The PCM will turn on the cooling tans when certain DTCs are set. These must be diagnosed before proceeding with the Cooling Fan System Check.
4. This step is a functional test of the system in order to determine the symptom, it any, present.