P0481
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 Control Circuit
Diagnostic Fault Information
Circuit/System Description
The engine cooling fan system consists of one cooling fan and two relays. The cooling fan has 2 windings in the motor, one winding is for low speed and the other winding is for high speed. The engine control module (ECM) grounds the low speed relay 1, and the high speed 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.
Conditions for Running the DTC
* The system 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.
* The DTCs run continuously once the conditions above have been met.
Conditions for Setting the DTC
* The ECM detects that the commanded state of the driver and the actual state of the control circuit do not match.
* The condition exists for greater than 30 seconds.
Action Taken When the DTC Sets
DTCs P0480 and P0481 are Type B DTCs.
Conditions for Clearing the 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.
* 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 (Diagrams)
Connector End View Reference
* Master Electrical Component List (A - Z Index)
* 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)
* Electrical Center Identification Views (Application and ID)
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) for scan tool information
Circuit/System Verification
1. Ignition ON, command each KR20 cooling fan relay ON and OFF with a scan tool. Listen or feel the relay click.
2. Engine operating, observe the DTC information with a scan tool. DTC P0480 and P0481 should not set.
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 both KR20 Cooling Fan Relays.
Note: The following tests must be performed on each fan relay.
2. Ignition ON, verify that a test lamp illuminates between ground and the relay coil B+ circuit terminal listed below:
* KR20C low speed COOL FAN 1 relay terminal 85
* KR20D high speed COOL FAN 2 relay terminal 85
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the output control circuit terminal 87 for a short to ground. If the circuit tests normal, test or replace the G10 engine cooling fan.
Note: The following tests must be performed on each fan relay.
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 low speed COOL FAN 1 relay terminal 86
* KR20D high speed COOL FAN 2 relay terminal 86
• 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 each fan relay.
4. Command the KR20 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 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 cooling fan relay.
Component Testing
1. Ignition OFF, disconnect the KR20 cooling fan relay.
2. Test for 70-110 ohm between terminals 85 and 86.
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. 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))
* Cooling Fan and Shroud Replacement (Service and Repair)
* Control Module References (Programming and Relearning)