DTC P0480, P0481, P0691, P0692, P0693, or P0694 3.8L (L26)

Diagnostic Instructions

DTC Descriptors

DTC P0480: Cooling Fan Relay 1 Control Circuit

DTC P0481: Cooling Fan Relay 2 Control Circuit

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Low Speed Cooling Fan Relay Control Circuit for Fan 1 Relay	P0480	P0480	P0480	--
Fan 1 Relay Coil Voltage Supply Circuit	P0480	P0480	P0480	--
High Speed Cooling Fan Relay Control Circuit for Fan 3 Relay	P0481	--	P0481	--
Fan 3 Relay Coil Voltage Supply Circuit	P0481	P0481	P0481	--
High Speed Cooling Fan Relay Control Circuit for Fan 2 Relay	P0481	--	P0481	--
Fan 2 Relay Coil Voltage Supply Circuit	P0481	P0481	P0481	--

Circuit/System Description

The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans receive positive voltage from the cooling fan relays which receive battery positive voltage from the underhood fuse block.

During low speed operation, the PCM supplies the ground path for the low speed fan relay, which is fan 1 relay, through the low speed cooling fan relay control circuit. This energizes the fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage from the fan 1 fuse through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the series/parallel relay, which is fan 2 relay, and the right cooling fan. The result is a series circuit with both fans running at low speed.

During high speed operation the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. The PCM grounds the high speed fan relay, which is fan 3 relay, and the series/parallel relay through the high speed cooling fan relay control circuit. This energizes the series/parallel relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the high speed fan relay coil is energized closing the relay contacts and provides battery positive voltage from the fan 2 fuse on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have their own ground path. The result is a parallel circuit with both fans running at high speed.

Conditions for Running the DTC

Conditions for Setting the DTC

Action Taken When the DTC Sets

DTCs P0480 and P0481 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0480 and P0481 are Type B 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. Verify with a scan tool that the PCM is not commanding fan relay activation.
2. Ignition ON, command each relay ON and OFF with a scan tool. Feel or listen to verify that each relay turns ON and OFF with each command.
3. Operate the vehicle within the Conditions for Running the DTC. 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 the series/parallel relay, which is fan 2 relay.
2. Connect a 30A fused jumper between the normally-open switch contact terminals at the series/parallel relay connector in order to complete the fan ground circuit. Leave this jumper in place for the remainder of this procedure.
3. Ignition OFF, disconnect the affected relay.
4. Ignition ON, connect a test lamp between the positive terminal at the battery and the affected relay control circuit terminal.
5. Command the affected 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 ON, test the relay control circuit for a short to ground. If the circuit tests normal, replace the PCM.

⇒	If the test lamp is always OFF, test the relay control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the PCM.

6. Connect a 30A fused jumper between the positive voltage terminal at the battery and the fan voltage supply circuit terminal at the affected relay connector and verify fan activation.

⇒	If the fan does not activate, test the fan voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the fan.

7. Ignition ON, connect a 30A fused jumper between the relay switch voltage supply circuit terminal and the fan voltage supply circuit terminal at the affected relay connector and verify fan activation.

⇒	If the fan does not activate, test the affected relay switch voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and its fuse is open, test all connected components and replace as necessary.

8. Ignition ON, verify that a test lamp illuminates between the affected relay coil voltage supply circuit and ground.

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

9. If all circuits and the PCM test normal, replace the affected relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

DTC P0480, P0481, P0691, P0692, P0693, or P0694 3.6L LY7

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 Circuit	P0691, P0693	P0480, P0481	--	--
Relay Switch Ignition Circuit	*	*	--	--
Fan Relay 1 Control Circuit	P0691	P0480	P0692	--
Fan Relay 2 and Fan Relay 3 Control Circuit	P0693	P0481	P0694	--
Relay Controlled Output Circuit	*	*	**	--
*Fans inoperative without a DTC. **Fans always ON without a DTC.

Typical Scan Tool Data

Cooling Fan Relays

Circuit	Short to Ground	Open	Short to Voltage
Operating Conditions: The engine is operating in closed loop Parameter Normal Operation: FC Relay Circuit Status: Indeterminate
FC Relay 1 Circuit Status	Fault	Fault	Fault
FC Relay 2 and 3 Circuit Status	Fault	Fault	Fault

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 low speed fan 1 relay. This energizes the coil and applies voltage directly to the left cooling fan through the switch side of the low relay. The left fan is connected in series to the right cooling fan through the de-energized series/parallel fan 2 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 low speed fan 1 relay, the series/parallel fan 2 relay, and the high speed fan 3 relay. When energized, the high speed fan 3 relay applies voltage directly to the right cooling fan through the switch side of the relay. Simultaneously, the low speed fan 1 relay and the series/parallel fan 2 relay provide ignition voltage and a direct path to ground for the left 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 low speed cooling fan 1 relay control circuit for more than 1 second.

P0481

The ECM detects an open circuit on the high speed cooling fan 2 relay control circuit for more than 1 second.

P0691

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

P0692

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

P0693

The ECM detects a short to ground on the high speed cooling fan 2 relay control circuit for more than 1 second.

P0694

The ECM detects a short to voltage on the high speed cooling fan 2 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 DTCs.

Conditions for Clearing the MIL/DTC

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

Reference Information

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Cooling System 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 three cooling fan relays.

Important:  The following test must be performed on all three fan relay circuits.

2. Ignition ON, verify that a test lamp illuminates between ground and the relay coil B+ circuit terminal listed below:

•	Low speed fan 1 relay terminal A19

•	High speed fan 3 relay terminal K19

•	Series/parallel fan 2 relay terminal K15

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

Important:  The following test must be performed on all three fan relay circuits.

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

•	Low speed fan 1 relay terminal C18

•	High speed fan 3 relay terminal M18

•	Series/parallel fan 2 relay terminal M14

⇒	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.

Important:  The following test must be performed on all three fan relay circuits.

4. Connect a test lamp between the relay coil control circuit and the relay coil ignition circuit terminals listed below:

•	Low speed fan 1 relay terminal C18 and terminal A19

•	High speed fan 3 relay terminal M18 and terminal K19

•	Series/parallel fan 2 relay terminal M14 and terminal K15

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.