For 1990-2009 cars

## DTC P0480, P0691, or P0692 2.0

### 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 Speed Output Circuit
DTC P0691: Cooling Fan Speed Output Circuit Low Voltage
DTC P0692: Cooling Fan Speed Output Circuit High Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Speed Control Circuit | P0691 | P0480 | P0692 | P0480

### Circuit/System Description

The engine cooling fan is a variable speed fan. The engine control module (ECM) controls the fan speed by sending a pulse width modulated (PWM) signal to the cooling fan control module. The cooling fan control module varies the voltage drop across the engine cooling fan motor in relation to the pulse width modulated signal. The cooling fan speed can be adjusted from 10 percent to 90 percent duty cycle. 90-94 percent is considered high speed fan.

The ECM monitors the voltage on the cooling fan speed control circuit driver output. Voltage is near B+ when the driver is OFF, and near ground when the driver is ON. If the difference between the actual and expected voltage exceeds a calibrated value, a DTC will set.

### Conditions for Running the DTC

• | The engine speed is more than 80 RPM.

• | The system voltage is between 10-18 volts.

### Conditions for Setting the DTC

#### P0480

The ECM detects 0 voltage on the output during commanded transitions.

#### P0691

The ECM detects low voltage on the output while commanded OFF.

#### P0692

The ECM detects high voltage on the output while commanded ON.

### Action Taken When the DTC Sets

DTC P0480, P0691, and P0692 are Type B DTCs.

### Conditions for Clearing the DTC

DTC P0480, P0691, and P0692 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

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

• | Electrical Center Identification Views

#### 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, verify with a scan tool that the ECM is not commanding fan activation.
2. Ignition ON, command the cooling fan speed from 10-90 percent with a scan tool. The fan speed should transition with the commanded states.

### Circuit/System Testing

1. Ignition OFF, disconnect the cooling fan speed control module.
2. Measure duty cycle with a DMM, set to trigger on the positive slope, between the cooling fan speed control circuit terminal 4 and ground.
3. Ignition ON, command the cooling fan speed from 10-100 percent with a scan tool while observing the DMM. The DMM should transition from 5-85 percent.

⇒ | If the DMM does not transition correctly, test the cooling fan speed control circuit for an open/high resistance, a short to voltage or a short to ground. If the circuit tests normal, replace the ECM.

4. If the ECM and the control circuit test normal, replace the cooling fan assembly.

### Repair Instructions

• | Cooling Fan and Shroud Replacement

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

### Repair Verification

1. Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
2. Ignition ON, command the cooling fan speed from 10-90 percent with a scan tool. The fan speed should transition with the commanded states.