Cooling Fan Always On

Cooling Fan Always On (with HP2)

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 Instructionsprovides an overview of each diagnostic category.

Circuit/System Description

The hybrid engine cooling fan system consists of two electrical cooling fans, two resistors, three engine control module (ECM) fan output control drivers, and five fan relays. The relays are arranged in a series/parallel configuration that allows the ECM to operate the fans at low, medium, or high speed depending on engine cooling requirements. The ECM controls the five relays by grounding the relay control circuits.

Diagnostic Aids

The ECM has the capability of providing command to the fan relays even while 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.

Reference Information
Schematic Reference

Engine Cooling Schematics Engine Cooling Schematics
Connector End View Reference

Component Connector End Views Connector Views
Description and Operation

Cooling Fan Description and Operation (Gas) Cooling Fan (Gas)
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

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference

Control Module References Control Module Referencesfor scan tool information

Circuit/System Verification

1. Verify that the following DTCs are not set: P0480, P0481, P0482.

• If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.

2. Verify with a scan tool that the ECM is not commanding fan relay activation.
3. Ignition ON, observe that the fans are not activated.

Circuit/System Testing

1. Ignition OFF, open the hood to disable the Auto-Stop function. Refer to Hybrid Modes of Operation Description Hybrid Modes of Operation Description.
2. Ignition ON, verify the scan tool hood position parameter displays Open.

• If the hood position does not display Open, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle for DTC P254F.

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

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

• If the fans are activated, test for a short to voltage in the relay controlled output circuit.
• If the fans are not activated, test or replace the appropriate cooling fan relay.

Component Testing

1. Ignition OFF, disconnect the cooling fan relay.
2. Test for 50-90 ohm between terminals 85 and 86.

• If not within the specified range, replace the cooling fan relay.

3. Measure the resistance between the terminals listed below:

* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87
The DMM should display OL.

• If less than the specified range, replace the cooling fan relay.

4. Test the Fan Control Relay for less than 2 ohm between terminals 30 and 87A.

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

5. Connect a 20 A fused jumper wire between relay terminal 85 and B+. Connect a jumper wire between relay terminal 86 and ground. Test for less than 2 ohm between terminals 30 and 87.

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

Repair Instructions

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

* Relay Replacement (Attached to Wire Harness) Relay Replacement (Attached to Wire Harness)Relay Replacement (Within an Electrical Center) Relay Replacement (Within an Electrical Center)
* Underhood Electrical Center or Junction Block Replacement Underhood Electrical Center or Junction Block Replacement