Diagnostic Instructions

DTC Descriptors

DTC P0480: Cooling Fan Relay 1 Control Circuit

DTC P0481: Cooling Fan Relay 2 Control Circuit

DTC P0691: Cooling Fan Relay 1 Control Circuit Low Voltage

DTC P0692: Cooling Fan Relay 1 Control Circuit High Voltage

DTC P0693: Cooling Fan Relay 2 Control Circuit Low Voltage

DTC P0694: Cooling Fan Relay 2 Control Circuit High Voltage

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Relay Coil Ignition Voltage	P0480, P0481, P0691, P0693	P0480, P0481, P0691, P0693	--	--
Relay Switch B+	*	*	--	--
Auxiliary Fan Relay Coil Control	P0481, P0691	P0481, P0691	P0481, P0692	--
Main Fan Relay and Fan Control Relay Coil Control	P0480, P0693	P0480, P0693	P0480, P0694	--
Relay Switch Controlled Output	*	*	**	--
* Fans inoperative without a DTC. ** Fans always ON without a DTC.

Circuit/System Description

The engine control module (ECM) 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. High speed has both fans turned ON at full speed.

In low speed operation, the ECM applies ground to the coil side of the auxiliary fan relay. This energizes the coil and applies voltage directly to the auxiliary cooling fan through the switch side of the relay. The auxiliary fan is connected in series to the main cooling fan through the de-energized series/parallel control fan relay. The series circuit operates both fans at low speed.

In high speed operation, the ECM applies a ground to the coil side of the auxiliary fan relay, the control fan relay, and the main fan relay. When energized, the main fan relay applies voltage directly to the main cooling fan through the switch side of the relay. Simultaneously, the auxiliary fan relay and the control fan relay provide ignition voltage and a direct path to ground for the auxiliary cooling fan. With both fans connected in a parallel circuit, each fan receives full voltage and operates at high speed.

Conditions for Running the DTC

Conditions for Setting the DTC

P0480

The ECM detects an open on the main cooling fan relay control circuit for more than 1 second.

P0481

The ECM detects an open circuit on the auxiliary cooling fan relay control circuit for more than 1 second.

P0691

The ECM detects a short to ground on the main cooling fan relay control circuit for more than 1 second.

P0692

The ECM detects a short to voltage on the main cooling fan relay control circuit for more than 1 second.

P0693

The ECM detects a short to ground on the auxiliary cooling fan relay control circuit for more than 1 second.

P0694

The ECM detects a short to voltage on the auxiliary cooling fan relay control circuit for more than 1 second.

Action Taken When the DTC Sets

DTCs P0480, P0481, P0691, P0692, P0693, and P0694 are Type B or Type C DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0480, P0481, P0691, P0692, P0693, and P0694 are Type B or Type C DTCs.

Reference Information

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Cooling Fan Description and Operation

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Ignition ON, command the appropriate fan relay ON and OFF with a scan tool. Listen or feel the relay click.
2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

1. Ignition OFF, disconnect all the cooling fan relays.

Important: The following tests must be performed on each cooling fan relay.

2. Ignition ON, verify that a test lamp illuminates between the relay coil ignition voltage circuit terminal 85 and ground.

⇒

If the test lamp does not illuminate, test the relay coil ignition voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal and the relay coil ignition voltage circuit fuse is open, test all components connected to the ignition voltage circuit and replace as necessary.

3. Test for 2.6-4.6 volts between the relay coil control circuit terminal 86 and ground.

⇒	If less than the specified range, test the relay coil control circuit for an open/high resistance or for a short to ground. If the circuit tests normal, replace the ECM.

⇒	If greater than the specified range, test the relay coil control circuit for a short to voltage. If the circuit tests normal, replace the ECM.

4. Connect a test lamp between the relay coil control circuit terminal 86 and the relay coil ignition voltage circuit terminal 85.
5. Command the fan relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always OFF, replace the ECM.

6. If all circuits test normal, test or replace the relay.

Component Testing

1. Ignition OFF, disconnect the cooling fan relay.
2. Test for 70-110 ohms 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 range, replace the relay.

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

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

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.