DTC P0480 or P0481 (LDK or LHU)
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DTC P0480 or P0481 (LDK or LHU)
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DTC P0480
Cooling Fan Relay 1 Control Circuit
DTC P0481
Cooling Fan Relays 2 and 3 Control Circuit
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Diagnostic Fault Information
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KR20C Cooling Fan Low Speed Relay
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Circuit
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Short to Ground
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Open/High Resistance
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Short to Voltage
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Signal Performance
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Relay Coil Ignition
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-
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P0481
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-
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-
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Relay Switch B+
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1
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1
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-
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-
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Relay Coil Control
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P0481
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P0481
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P0481
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-
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Relay Controlled Output
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1
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1
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2
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-
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1.
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Left fan inoperative without a DTC.
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2.
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Low speed fan always ON without a DTC.
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KR20D Cooling Fan High Speed Relay
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Circuit
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Short to Ground
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Open/High Resistance
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Short to Voltage
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Signal Performance
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Relay Coil Ignition
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P0481
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3
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1
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-
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Relay Switch B+
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2
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3
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-
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-
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Relay Coil Control
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P0481
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P0481
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P0481
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-
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Relay Controlled Output
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2
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3
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4
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-
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1.
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Left fan Low speed replaced by high speed without a DTC.
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2.
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Left fan inoperative at Medium and High speed, without a DTC.
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3.
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Left fan High speed inoperative without a DTC.
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4.
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Left fan always ON at High speed, without a DTC.
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KR20E Cooling Fan Speed Control Relay
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Circuit
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Short to Ground
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Open/High Resistance
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Short to Voltage
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Signal Performance
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Relay Coil Ignition
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P0480
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1
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-
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-
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Relay Switch Ignition
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P0480
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1
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-
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-
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Relay Coil Control
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2
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1
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-
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-
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Relay Controlled Output
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P0480
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1
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2
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-
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1.
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Right fan inoperative at High speed, without a DTC.
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2.
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Right fan operates at High speed only, without a DTC.
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KR20F Cooling Fan Relay
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Circuit
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Short to Ground
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Open/High Resistance
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Short to Voltage
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Signal Performance
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Relay Coil Ignition
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P0480
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P0480
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-
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-
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Relay Switch B+
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1
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2
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-
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-
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Relay Coil Control
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P0480
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P0480
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P0480
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-
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Relay Controlled Output
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-
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2
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-
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-
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1.
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Low speed fan inoperative without a DTC.
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2.
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Medium and High speed fans inoperative without a DTC.
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Cooling Fan Relay 1, and Cooling Fan Relays 2 and 3 Control Circuit Open, Low Voltage, and High Voltage Test Status
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Circuit
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Short to Ground
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Open
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Short to Voltage
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Operating Conditions:
Component Commanded OFF
Parameter Normal Range:
The following illustrates the normal parameter state with no circuit conditions:
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•
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Component OFF - OK for Open/Low Voltage test and Not Run for High Voltage test
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•
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Component ON - Not Run for Open/Low Voltage test and OK for High Voltage test
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Ignition Voltage
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-
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Malfunction
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-
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KR20C Cooling Fan Low Speed Relay Control
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Malfunction
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Not Run
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-
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KR20D Cooling Fan High Speed Relay Control
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Malfunction
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Not Run
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-
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KR20F Cooling Fan Relay Control
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Malfunction
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Malfunction
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Not Run
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Cooling Fan Relay 1, and Cooling Fan Relays 2 and 3 Control Circuit Open, Low Voltage, and High Voltage Test Status
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Circuit
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Short to Ground
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Open
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Short to Voltage
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Operating Conditions:
Component Commanded ON
Parameter Normal Range:
The following illustrates the normal parameter state with no circuit conditions:
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•
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Component OFF - OK for Open/Low Voltage test and Not Run for High Voltage test
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•
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Component ON - Not Run for Open/Low Voltage test and OK for High Voltage test
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Ignition Voltage
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Not Run
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Not Run
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-
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KR20C Cooling Fan Low Speed Relay
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Not Run
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Not Run
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Malfunction
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KR20D Cooling Fan High Speed Relay Control
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Not Run
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Not Run
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Malfunction
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KR20F Cooling Fan Relay Control
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Not Run
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Not Run
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Malfunction
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Circuit/System Description
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The engine cooling fan system is composed of two fans, 7 relays, the engine control module (ECM), and the associated wiring. Each fan assembly includes one resistor, which enables the ECM to operate the engine cooling fans at 3 speeds using two control circuits. The ECM activates the applicable relay by grounding the control circuit with a solid state device called a driver. Each driver is equipped with a feedback circuit that is pulled-up to a voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. 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 G106.
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Conditions for Running the DTC
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The ignition voltage is between 11-32 V.
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The engine speed is greater than 400 RPM.
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The ECM driver transitions from ON to OFF or from OFF to ON.
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DTC P0480 and P0481 run continuously when the conditions above are met.
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Conditions for Setting the DTC
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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.
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Action Taken When the DTC Sets
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DTCs P0480 and P0481 are Type B DTCs.
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Conditions for Clearing the MIL/DTC
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DTCs P0480 and P0481 are Type B DTCs.
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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.
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•
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The scan tool cooling fan output control operates as follows:
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-
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Cooling Fan Relay 1 operates both fans at a medium speed
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-
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Cooling Fan Relays 2 and 3 operates both fans at a low speed
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-
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Cooling Fan Relays 1, 2 and 3 operates both fans at a high speed
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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.
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A condition with the powertrain relay may set DTC P0481 or P0693.
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Schematic Reference
Engine Cooling Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Cooling Fan Description and Operation (LHU/A20NFT, LAU/A28NER)
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References
for scan tool information
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Circuit/System Verification
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1.
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With the engine running, check the DTC Info with a scan tool. DTC P0480 or P0481 are not set.
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2.
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Command the cooling fans ON and OFF at low, medium, and high speed while observing the scan tool circuit test status parameters listed below:
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Cooling Fan Relay 1 Control Circuit Open, Low Voltage, and High Voltage Test Status
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•
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Cooling Fan Relays 2 and 3 Control Circuit Open, Low Voltage, and High Voltage Test Status
The parameters should display OK or Not Run in each of the commanded states.
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3.
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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.
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1.
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Ignition OFF, disconnect the KR20 cooling fan relays listed below:
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KR20F cooling fan relay
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•
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KR20C cooling fan low speed relay
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•
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KR20D cooling fan high speed relay
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2.
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Ignition ON, connect a test lamp between ground and the relay coil ignition voltage circuit terminal listed below. The test lamp should turn ON.
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•
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KR20F cooling fan relay terminal 85
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KR20C cooling fan low speed relay terminal 86
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3.
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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.
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4.
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Note
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The following tests must be performed on all three fan relay control circuits.
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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.
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•
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KR20F cooling fan relay terminal 86
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•
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KR20C cooling fan low speed relay terminal 85
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•
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KR20D cooling fan high speed relay terminal 85
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5.
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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.
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6.
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Note
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The following test must be performed on all three fan relay circuits.
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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.
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7.
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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.
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8.
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If all circuits test normal, test or replace the appropriate KR20 relay.
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1.
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Ignition OFF, disconnect the cooling fan relay.
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2.
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Test for 70-110 Ω between terminals 85 and 86.
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3.
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If not within the specified range, replace the KR20 cooling fan relay.
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4.
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Measure the resistance between the terminals listed below. The DMM should display OL.
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•
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If less than the specified range, replace the KR20 cooling fan relay.
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5.
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Install a 20 A fused jumper wire between relay terminal 85 and B+. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 Ω between terminals 30 and 87.
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6.
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If greater than the specified range, replace the KR20 cooling fan relay.
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Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
