Cooling Fan Always On

Cooling Fan Always On (2.4L RPO-LAX)

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

Circuit/System Description

The powertrain control module (PCM) controls cooling fan operation in either high speed or low speed mode, depending on cooling requirements. To activate a fan, the PCM applies ground to the coil side of the applicable fan relays. This energizes the coil and applies voltage directly to the cooling fan through the switch side of the relay.

Diagnostic Aids

* The fan relay electrical contacts may be pitted or sticking. Replace the relay, if tapping gently on the relay, or wiggling the relay causes a change in the relays operation.
* The performance of the cooling relay may be affected by temperature. Check the relay after sitting outside overnight and after running the engine 30 minutes.

Use the following relay cavity table in order to locate the correct cavities to probe during diagnosis. The table layout corresponds to the cavity layout of the relay block.














Reference Information
Schematic Reference

Engine Cooling Schematics (Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Cooling Fan Description and Operation (Cooling Fan Description and Operation)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

1. Verify the HVAC system operates correctly.

• If an HVAC system condition is found, repair the HVAC condition first. Refer to Symptoms - HVAC Systems - Manual (Symptoms - HVAC Systems - Manual).

2. Ignition ON, observe that the fan is not activated.

Circuit/System Testing

Important: The following tests must be performed on each cooling fan relay.


1. Ignition OFF, disconnect each cooling fan relay one at a time.
2. Ignition ON, observe that the cooling fans are not activated.

• If the fan is activated, test for a short to voltage in the relay controlled output circuit.
• If the fan is not activated, test for a short to ground in the relay coil control circuits.

3. If all circuits test normal, test or replace the cooling fan relay.

Component Testing

1. Ignition OFF, disconnect the relay.
2. Test for 85-120 ohms at 20°C (68°F) between terminals 1 and 2.

• If the resistance is not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

* 5 and 1
* 5 and 2
* 5 and 3
* 1 and 3
* 2 and 3

• If not the specified range, replace the relay.

4. Test for less than 2 ohms between terminals 3 and 4.

• If greater than the specified range, replace the relay.

5. Install a 20A fused jumper wire between relay terminal 1 and 12 volts. Install a jumper wire between relay terminal 2 and ground. Test for less than 2 ohms between terminals 3 and 5.

• If greater than the specified range, replace the relay.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.