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DTC P0481 (w/LF1)

DTC P0481 (w/LF1)

Diagnostic Instructions


• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• Diagnostic Procedure Instructions provides an overview of each diagnostic category.


DTC Descriptors

DTC P0481

Cooling Fan Relays 2 and 3 Control Circuit

Diagnostic Fault Information

KR20P COOL FAN 2 Relay

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
Relay Coil Ignition Circuit P0480, P0481 P0481 - -
Relay Switch B+ Circuit 1 2 - -
Relay Control Circuit P0481 P0481 P0481 -
Relay Controlled Output Circuit 1 2 3 -

1. Low and medium speed fan inoperative without a DTC.

2. Medium speed fan inoperative without a DTC.

3. Medium speed fan always ON without a DTC.




KR20C COOL FAN 3 Relay

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
Relay Coil Ignition Circuit P0480 2 - -
Relay Switch B+ Circuit 1 2 - -
Relay Control Circuit 3 2 4 -
Relay Controlled Output Circuit 1 2 3 -

1. Low and medium speed fan inoperative without a DTC.

2. Low speed fan inoperative without a DTC.

3. Low speed fan always ON without a DTC.

4. Low and high speed fan inoperative without a DTC.




KR20D COOL FAN 1 Relay

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
Relay Coil Ignition Circuit P0480, P0481 P0481 1 -
Relay Switch B+ Circuit 2 2 - -
Relay Control Circuit P0481 P0481 P0481 -
Relay Controlled Output Circuit 2 2 3 -

1. Medium speed fan replaced by high speed fan without a DTC.

2. High speed fan inoperative without a DTC.

3. High speed fan always ON without a DTC.




KR20E COOL FAN 5 Relay

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
Relay Coil Ignition Circuit P0480 1 - -
Relay Switch Ignition Circuit P0480 1 - -
Relay Control Circuit 2 1 3 -
Relay Controlled Output Circuit P0480, P0481 1 4 -

1. High speed fan inoperative without a DTC.

2. Low speed fan always ON without a DTC.

3. Low and high speed fan inoperative without a DTC.

4. Medium speed fan inoperative without a DTC.




KR20F COOL FAN 4 Relay

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
Relay Coil Ignition Circuit P0480 P0480 - -
Relay Switch Ignition Circuit 1 2 - -
Relay Control Circuit P0480 P0480 P0480 -
Relay Controlled Output Circuit - 2 - -

1. Low speed fan always ON without a DTC.

2. Low speed fan and high speed fan inoperative.




Typical Scan Tool Data

Cooling Fan Relay 1 and Cooling Fan Relays 2 and 3 Control Circuit Open, Low, and High Voltage Test Status

Circuit Short to Ground Open Short to Voltage
Operating Conditions: Component Commanded OFF Parameter Normal Range: The following illustrates the normal parameter state with no circuit conditions:
• Component OFF - OK for Open/Low Voltage test and Not Run for High Voltage test

• Component ON - Not Run for Open/Low Voltage test and OK for High Voltage test


Ignition Voltage Circuit Malfunction Malfunction -
Cooling Fan Relays 1 and 2 Control Circuit Malfunction Malfunction Not Run
Cooling Fan Relay 4 Control Circuit Malfunction Malfunction Not Run



Cooling Fan Relays 1, 2 and 3 Control Circuit Open, Low, and High Voltage Test Status

Circuit Short to Ground Open Short to Voltage
Operating Conditions: Component Commanded ON Parameter Normal Range: The following illustrates the normal parameter state with no circuit conditions:
• Component OFF - OK for Open/Low Voltage test and Not Run for High Voltage test

• Component ON - Not Run for Open/Low Voltage test and OK for High Voltage test


Ignition Voltage Circuit Not Run Not Run -
Cooling Fan Relays 1 and 2 Control Circuit Not Run Not Run Malfunction
Cooling Fan Relay 4 Control Circuit Not Run Not Run Malfunction


Circuit/System Description

The engine cooling fan system is composed of one cooling fan, a series of 5 relays, the engine control module (ECM), and the associated wiring. The cooling fan assembly includes two individual resistors mounted to each side of the cooling fan shroud. This combination of components enables the ECM to operate the cooling fan at 3 speeds using two fan control circuits.

To operate the fan, the ECM activates the applicable relay by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage.

Conditions for Running the DTC


• The ignition voltage is between 11-32 volts.

• The engine speed is greater than 400 RPM.

• The ECM driver transitions from ON to OFF or from OFF to ON.

• DTC P0481 runs continuously when the conditions above are met.


Conditions for Setting the DTC

P0481

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

Action Taken When the DTC Sets

DTC P0481 is a Type B DTC.

Conditions for Clearing the MIL/DTC

DTC P0481 is a Type B DTC.

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 scan tool Cooling Fan Relay Command parameters to know which fans are being commanded ON by the ECM.

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

- Cooling Fan Relay 1 operates the fan at a low speed

- Cooling Fan Relay 2 and 3 operates the fan at a medium speed

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

• 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

Connector End View Reference

Component Connector End Views

Description and Operation

Cooling Fan Description and Operation (LF1) Cooling Fan Description and Operation (LAU)

Electrical Information Reference


• Circuit Testing

• Connector Repairs

• Testing for Intermittent Conditions and Poor Connections

• Wiring Repairs


DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification


1. Ignition ON, observe the scan tool parameters listed below. Command the cooling fan ON and OFF with a scan tool. The parameters should display OK or Not Run in each of the commanded states.

• Cooling Fan Relay 2 and 3 Open Circuit Test Status

• Cooling Fan Relay 2 and 3 Low Voltage Test Status

• Cooling Fan Relay 2 and 3 High Voltage Test Status

2. Engine on, check the DTC information with a scan tool. DTC U0481 should not be 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 the KR20 cooling fan relays listed below:

• KR20P COOL FAN 2 Relay 9

• KR20D COOL FAN 1 Relay 13

2. Ignition ON, verify that a test lamp illuminates between ground and the KR20P relay coil ignition circuit terminal 86.

3. If the test lamp does not illuminate, test the relay coil ignition circuit for an open/high resistance.

4.
Note

The following tests must be performed on each relay control circuit.


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.

• KR20P COOL FAN 2 relay terminal 85

• KR20D COOL FAN 1 relay terminal 86

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

6.
Note

The following test must be performed on each relay control circuit.


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

• KR20P COOL FAN 2 relay terminal 85

• KR20D COOL FAN 1 relay terminal 86

7. 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.

8. 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 60-100 Ω between terminals 85 and 86.

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

4. 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.

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 Ω between terminals 30 and 87.

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


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


• Relay Replacement (Attached to Wire Harness) Relay Replacement (Within an Electrical Center)

• Control Module References for ECM replacement, setup, and programming