Cooling Fan Always On 2.2L and 2.4L

The engine control module (ECM) grounds the low speed relay, which is relay 1, and the high speed relay, which is relay 2, control circuits through an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line that is monitored by the ECM. When the ECM is commanding a component ON, the voltage potential of the control circuit should be low, near 0 volts. When the ECM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be high, near battery voltage. If the ECM detects that the actual state of the control circuit does not match the expected state, a DTC will set.

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

Description and Operation

Cooling Fan Description and Operation

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

1. If DTCs P0480 or P0481 are set, then perform those diagnostics first.
2. Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
3. Ignition ON, observe that the fan is not activated.

Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

1. Ignition OFF, disconnect the relays.
2. Ignition ON, observe that the fan is not activated.

⇒	If the fan is not activated, replace the faulty relay.

⇒	If the fan is activated, test the fan voltage supply circuits for a short to voltage.

1. Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
2. Ignition ON, observe that the fan is not activated.

Cooling Fan Always On 3.5L

The powertrain control module (PCM) commands the fans ON in either high speed or low speed, depending on cooling requirements. In low speed, both fans are turned ON at a reduced speed. In high speed, both fans are turned ON at full speed.

In low speed operation, the PCM applies a ground to the coil side of the cooling fan 1 or low speed relay. This energizes the coil and applies voltage directly to the left or low speed cooling fan through the switch side of the relay. The left or low speed cooling fan is connected in series to the right or high speed cooling fan through the normally closed contacts of the cooling fan 3 or the cooling fan control relay. The series circuit operates both fans at low speed.

In high speed operation, the PCM applies a ground to the coil side of all three cooling fan relays. This action applies voltage directly to the right or high speed cooling fan through the switch side of the cooling fan 2 or high speed relay. Simultaneously, the cooling fan 1 or low speed relay provides voltage to the left or low speed cooling fan, while the cooling fan 3 or control relay provides a direct path to ground for the left or low speed cooling fan. With both fans connected in a parallel circuit, each fan receives full voltage and operates at high speed.

The following two tables illustrate the COOLING FAN 1 relay and the COOLING FAN 2 relay terminal locations in the underhood fuse block. The third table illustrates the COOLING FAN 3 relay terminal locations in the relay electrical connector.

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

Description and Operation

Cooling Fan Description and Operation

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

1. Verify that the following DTCs are not set: P0480, P0481, P0691, P0692, P0693 or P0694.

⇒	If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

2. Ignition ON, verify with a scan tool that the PCM is not commanding fans ON.
3. Ignition ON, observe that the fans are not activated.
4. If the vehicle passes the Circuit/System Verification test, then operate the vehicle within the conditions that the concern was detected.

1. Ignition OFF, disconnect each cooling fan relay one at a time.
2. Ignition ON, observe that the cooling fans are OFF.

⇒	If the fans are ON, test for a short to voltage in the relay switch supply circuit.

⇒	If the fans are OFF, test or replace the applicable cooling fan relay.

1. Ignition OFF, disconnect the cooling fan relay.
2. Test for 70-110 ohms of resistance between terminals 85 and 86.

⇒	If the resistance is not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

•

30 and 86

•

30 and 87

•

30 and 85

•

85 and 87

⇒	If not the specified value, replace the relay.

4. Test for less than 2 ohms of resistance between terminals  30 and 87A.

⇒	If greater than the specified range, replace the relay.

5. Install a 20A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms of resistance between terminals 30 and 87.

⇒	If greater than the specified range, replace the relay.

Ignition ON, command the fan relays ON and OFF with a scan tool. Verify the appropriate fan turns ON and OFF with each command.

1. Ignition ON, observe that the fans are not activated.
2. Ignition ON, command the fan relays ON and OFF with a scan tool. Verify the appropriate fan turns ON and OFF with each command.