For 1990-2009 cars

## DTC P0480 or P0481 2.4

### 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: Low Speed Cooling Fan Relay Control Circuit
DTC P0481: High Speed Cooling Fan Relay Control Circuit

### Diagnostic Fault Information

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

### Circuit/System Description

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.

### Conditions for Running the DTC

• | The ignition is ON.

• | The system voltage is between 9-18 volts.

### Conditions for Setting the DTC

• | An improper voltage level has been detected on the cooling fan relay control circuit.

• | The condition must be present for a minimum of 30 seconds.

### Action Taken When the DTC Sets

• | DTC P0480 is a Type B DTC.

• | DTC P0481 is a Type B DTC.

### Conditions for Clearing the DTC

• | DTC P0480 is a Type B DTC.

• | DTC P0481 is a Type B DTC.

### 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

• | Circuit Testing

• | Connector Repairs

• | Electrical Center Identification Views

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

Verify cooling fan operation using the scan tool commands listed below:

• | Fan Relay 1 ON and Fan Relay 2 OFF--Fan runs at low speed.

• | Fan Relay 1 OFF and Fan Relay 2 ON--Fan runs at high speed.

### Circuit/System Testing

1. Ignition OFF, disconnect the affected relay.
2. Verify that a test lamp illuminates between the B+ circuit terminal listed below and ground:

• | Cool Fan Relay, terminal 85

• | Cool Fan 2 Relay, terminal 86

⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and its fuse is open, test the control circuit terminal listed below for a short to ground. If the circuit tests normal, replace the relay.

• | Cool Fan Relay, terminal 85

• | Cool Fan 2 Relay, terminal 86

3. Test for 70-110 ohms between terminal 85 and terminal 86 of the relay.

⇒ | If not within the specified range, replace the relay.

4. Test for 0.0A with a DMM connected in series with the relay coil between circuit terminal 85 and circuit terminal 86 at the relay connector.

⇒ | If more than the specified value, test the control circuit terminal listed below for a short to ground. If the circuit tests normal, replace the ECM.

• | Cool Fan Relay, terminal 85

• | Cool Fan 2 Relay, terminal 86

5. Command the relay ON with a scan tool. Verify that the DMM indicates more than 100 mA.

⇒ | If not the specified range, test the control circuit terminal listed below for an open/high resistance. If the circuit tests normal, replace the ECM.

• | Cool Fan Relay, terminal 85

• | Cool Fan 2 Relay, terminal 86

6. If all circuits and the ECM test normal, replace the affected relay.

### Repair Instructions

Cooling Fan and Shroud Replacement

### Repair Verification

Ignition ON, command the relay ON and OFF with a scan tool. Feel or listen to verify that the relay turns ON and OFF with each command.