For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### 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

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

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 Relay

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: The engine is operating in closed loop Parameter Normal Operation: FC Relay xx 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

• | The ignition voltage is between 8-18 volts.

• | The engine speed is more than 40 RPM.

• | The ECM driver transitions from ON to OFF or from OFF to ON.

### 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.

### Diagnostic Aids

• | The ECM has the capability of providing command to the fan relays even when a scan tool output control is being used. Always refer to the fan control command parameters on the scan tool to know which fans are being commanded ON by the ECM.

• | The following tables illustrate the FAN 1 relay, FAN 2 relay and the FAN 3 relay terminal locations in the underhood fuse block:

#### Cooling FAN 1 Relay

Terminal Identification
Relay Switch B+ | Relay Coil Control
Relay Coil B+ | Relay Controlled Output
Front of Vehicle

#### Cooling FAN 2 Relay

Terminal Identification
Relay Switch B+ | Relay Coil Control
-- | Relay Controlled Output
Relay Coil B+ | Ground
Front of Vehicle

#### Cooling FAN 3 Relay

Terminal Identification
Relay Coil Control | Relay Controlled Output
Relay Switch B+ | Relay Coil B+
Front of Vehicle

### Reference Information

#### Schematic Reference

Engine Cooling Schematics

#### Connector End View Reference

Cooling System Connector End Views

#### Description and Operation

Cooling System Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

### 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 tests must be performed on all three fan relay circuits.

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

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

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

3. Test for 2.6-4.6 volts between the relay coil control circuit 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.

Important: The following tests 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.
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 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 range, 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.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Relay Replacement

• | Control Module References for ECM replacement, setup, and programming