For 1990-2009 cars

## Cooling Fan Inoperative 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.

### 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.

### 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

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. If DTCs P0480, P0691, or P0692 are set, perform that diagnostic first.
2. Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
3. 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

Important: The Circuit/System Verification must be performed first or misdiagnosis may result.

1. Ignition OFF, disconnect the cooling fan.
2. Ignition OFF, measure between ground and the cooling fan ground circuit terminal 2 at the engine harness connector for less than 1 ohm of resistance.

⇒ | If more than 1 ohm, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the cooling fan voltage supply circuit terminal 1 and ground. The lamp should illuminate.

⇒ | If the lamp does not illuminate, test the voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and its fuse is open, replace the cooling fan assembly.

4. If all circuits 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.

## Cooling Fan Inoperative 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.

### 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.

### 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

### Circuit/System Verification

1. If DTCs P0480 or P0481 are set, then perform those diagnostics first.
2. Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
3. Ignition ON, observe that the fan is not activated.

### Circuit/System Testing

Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

1. Ignition OFF, disconnect the relays.
2. Ignition ON, observe that the fan is not activated.

⇒ | If the fan is not activated, replace the faulty relay.

⇒ | If the fan is activated, test the fan voltage supply circuits for a short to voltage.

### Repair Instructions

Cooling Fan and Shroud Replacement

### Repair Verification

1. Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
2. Ignition ON, observe that the fan is not activated.