P0480
DTC P0480 or P0481
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.
DTC Descriptors
DTC P0480
- Cooling Fan Relay 1 Control Circuit
DTC P0481
- Cooling Fan Relay 2 and 3 Control Circuit
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The engine cooling fan system consists of 2 electric cooling fans and 3 fan relays. The cooling fan relays are arranged in a series/parallel (S/P) configuration. This allows the engine control module (ECM) to operate both fans together at low or high speeds using 2 fan control circuits. The cooling fans receive positive voltage from the cooling fan relays, which receive battery positive voltage from the underhood fuse block. The cooling fans are supplied a ground at G100 and G101.
Conditions for Running the DTC
* The system voltage is between 9-18 volts.
* The engine speed is greater than 400 RPM.
* DTCs P0480 and P0481 run continuously when the conditions above are met.
Conditions for Setting the DTC
* The commanded state of the ECM driver and the actual state of the control circuit do not match.
* The condition exists 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 ECM has the capability of providing command to the fan relays even when 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.
* The scan tool cooling fan output control operates as follows:
- Fan Relay 1 operates both fans at a low speed
- Fan Relay 2 and 3 operates one fan at high speed
- Fan Relays 1, 2, and 3 operates both fans at high speed
Reference Information
Schematic Reference
Engine Cooling Schematics [1][2]Cooling System
Connector End View Reference
* Component Connector End Views Connector End Views By Name
* Powertrain Component Views Top of Engine Components (except LZ1)
* Electrical Center Identification Views Application and ID
Description and Operation
Cooling Fan Description and Operation Cooling Fan
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 Programming and Relearning
Circuit/System Verification
1. Engine operating, observe the DTC information with a scan tool. DTC P0480 or P0481 should not be 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 the 3 cooling fan relays listed below.
* FAN LO relay
* FAN CNTRL relay
* FAN HI relay
2. Ignition ON, verify that a test lamp illuminates between ground and the ignition circuit terminal 85 of each relay.
• If the test lamp does not illuminate, test the ignition circuit for an open/high resistance.
3. Set the DMM on the diode setting. Connect the black lead to ground. Connect the red lead of the DMM to a control circuit terminal listed below:
* FAN LO Relay terminal 86
* FAN CNTRL Relay terminal 86
* FAN HI Relay terminal 86
The DMM should display OL.
• 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.
4. Command the appropriate 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:
* 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 KR20 cooling fan relay.
4. Test the KR20 Fan Control Relay for less than 2 ohm between terminals 30 and 87A.
• If greater than the specified range, replace the fan control 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
* Underhood Electrical Center or Junction Block Replacement Underhood Electrical Center or Junction Block Replacement
* Engine Coolant Fan Replacement
* Control Module References Programming and Relearningfor ECM replacement, setup, and programming