Operation CHARM: Car repair manuals for everyone.

Dual Fan




DTC P0480 or P0481 (Dual Fan)

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.

DTC Descriptors
DTC P0480
- Cooling Fan Relay 1 Control Circuit

DTC P0481
- Cooling Fan Relays 2 and 3 Control Circuit

Diagnostic Fault Information






Typical Scan Tool Data











Circuit/System Description

The engine cooling fan system consists of one electrical cooling fan, a serviceable resistor module mounted in the cooling fan shroud, and three fan relays. The relays are arranged in a series parallel (S/P) configuration that allows the engine control module (ECM) to operate the fan at low, medium, or high speeds, depending on cooling requirements. The resistor module is a self-contained unit providing a specific resistance through three individual circuits. To activate the fan, the ECM applies ground to the coil side of the applicable fan relays. The cooling fan and fan relays receive battery voltage from the underhood fuse block. The ground path for the operation of the cooling fan is provided at G104.

Conditions for Running the DTC

* The ignition voltage is between 11-18 volts.
* The engine speed is greater than 400 RPM.
* The ECM driver transitions from ON to OFF or from OFF to ON.
* DTC P0480 and P0481 run continuously when the conditions above are met.

Conditions for Setting the DTC

P0480

The commanded state of the ECM driver and the actual state of the control circuit do not match for greater than 5 seconds.

P0481

The commanded state of the ECM driver and the actual state of the control circuit do not match for greater than 5 seconds.

Action Taken When the DTC Sets

DTCs P0480 and P0481 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0480 and P0481 are Type B DTCs.

Diagnostic Aids

* The scan tool cooling fan output control operates as follows:

- Fan Relay 1 operates the fan at a low speed
- Fan Relay 2 and 3 operates the fan at a medium speed
- Fan Relay 1, 2 and 3 operates the fan at a high speed

* KR20 cooling fan relay identification:

- KR20C cooling fan low speed FAN 1 Relay
- KR20D cooling fan high speed FAN 2 Relay
- KR20E cooling fan speed control FAN 3 or S/P Relay

* When disconnecting or removing fuses and relays from a fuse block, always inspect the component electrical terminals for corrosion and the correct orientation in the fuse block. Test the mating electrical terminals for tightness.

Reference Information
Schematic Reference

Engine Cooling Schematics [1][2]Cooling System
Connector End View Reference

* Component Connector End Views Connector Views
* Electrical Center Identification Views Fuse Block - Underhood Label (North America)

Description and Operation

Cooling Fan Description and Operation 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

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. Engine operating, observe the DTC information with a scan tool. DTC P0480 and P0481 should not set.
2. Command the cooling fans ON and OFF at high speed while observing the scan tool circuit test status parameters listed below:

* FC Relay 1 Ckt Open, Short Gnd, and Short Volts Test Status
* FC Relay 2 and 3 Ckt Open, Short Gnd, and Short Volts Test Status
The parameters should display OK or Not Run in each of the commanded states.

3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

1. Ignition OFF, disconnect all of the KR20 cooling fan relays.

Note: The following tests must be performed on all three fan relay circuits.

2. Ignition ON, verify that a test lamp illuminates between ground and the relay coil ignition circuit terminal listed below:

* KR20C cooling fan low speed relay terminal 85
* KR20D cooling fan high speed relay terminal 85
* KR20E cooling fan speed control relay terminal 86

If the test lamp does not illuminate, test the relay coil ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the relay coil ignition circuit fuse is open, test all components connected to the ignition circuit and replace as necessary.

Note: The following test must be performed on all three fan relay control circuit terminals.

3. Connect the red lead of the DMM to a control circuit terminal listed below. Connect the black lead to ground. Set the DMM on the diode setting. The DMM should display OL.

* KR20C cooling fan low speed relay terminal 86
* KR20D cooling fan high speed relay terminal 86
* KR20E cooling fan speed control relay terminal 85

If less than the specified range, test the appropriate relay coil control circuit for a short to ground. If the circuit tests normal, replace the K20 ECM.

Note: The following tests must be performed on all three fan relay circuits.

4. Command the cooling fan relay ON and OFF with a scan tool. The DMM should transition from OL when commanded OFF to less than 1 V when commanded ON.

If the circuit voltage does not correspond to the specified values, test the control circuit for an open/high resistance or for a short to voltage. If the circuit tests normal, replace the K20 ECM.

5. If all circuits test normal, test or replace the appropriate KR20 relay.

Component Testing

1. Ignition OFF, disconnect the KR20 cooling fan relay.
2. Test for 70-110 ohm between terminals 85 and 86.

If not within the specified range, replace the KR20 cooling fan relay.

3. Measure the resistance between the terminals listed below. The DMM should display OL.

* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87

If less than the specified range, replace the KR20 cooling fan relay.

4. Test for less than 2 ohm between terminals 30 and 87A.

If greater than the specified range, replace the KR20E 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 KR20 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)
* Control Module References Control Module Referencesfor ECM replacement, setup, and programming