The engine control module (ECM) commands the fan ON in either high speed or low speed, depending on cooling requirements.

In low speed operation, the ECM supplies a ground to the coil side of the low speed fan relay. This energizes the coil and applies voltage directly to the cooling fan through the switch side of the low relay. The fan is connected in series to the cooling fan resistor causing the fan to operate at low speed.

In high speed operation, the ECM supplies a ground to the coil side of the fan high or fan control relay. When energized, the fan high or control relay applies voltage directly to the cooling fan through the switch side of the relay. The ECM commands the low speed fan relay OFF and the cooling fan receives full voltage and operates at high speed.

The ECM detects that the commanded state of the driver and the actual state of the control circuit do not match for greater than 2 s.

DTCs P0480 00 and P0481 00 are Type B DTCs.

DTCs P0480 00 and P0481 00 are Type C DTCs.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Cooling System Description and Operation

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for diagnostic tester information

1. Ignition ON, command the appropriate KR20C Cooling Fan Low Speed Relay, KR20D Cooling Fan High Speed Relay, or KR20A Cooling Fan Medium Speed Relay ON and OFF with a scan tool. You should hear the relay click when commanded ON and OFF.
2. 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.

1. Ignition OFF, disconnect the KR20F Cooling Fan Relay, KR20D Cooling Fan High Speed Relay, or KR20A Cooling Fan Medium Speed Relay.
2. Ignition ON, verify that a test lamp illuminates between the KR20F Cooling Fan Relay, KR20D Cooling Fan High Speed Relay, or KR20A Cooling Fan Medium Speed Relay coil ignition circuit terminal 85 and ground.

⇒

If the test lamp does not illuminate, test the KR20F Cooling Fan Relay, KR20D Cooling Fan High Speed Relay, or KR20A Cooling Fan Medium Speed Relay coil ignition circuit for a short to ground or an open / high resistance. If the circuit tests normal and the KR20F Cooling Fan Relay, KR20D Cooling Fan High Speed Relay, or KR20A Cooling Fan Medium Speed Relay coil ignition circuit fuses F42, F45, or F46 for an open, test all components connected to the ignition circuit and repair and replace as necessary.

3. Connect a test lamp between the KR20F Cooling Fan Relay, KR20D Cooling Fan High Speed Relay, or KR20A Cooling Fan Medium Speed Relay coil control circuit terminal 86 and B+.
4. Command the Cooling Fan Relay 1 Command, Cooling Fan Relay 2 Command, Cooling Fan Relay 3 Command ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states for the appropriate relay.

⇒	If the test lamp is always ON, test the KR20F Cooling Fan Relay, KR20D Cooling Fan High Speed Relay, or KR20A Cooling Fan Medium Speed Relay coil control circuit for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

⇒	If the test lamp is always OFF, test the relay coil control circuit for a short to voltage or an open / high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

5. If all circuits test normal, test or replace the KR20F Cooling Fan Relay, KR20D Cooling Fan High Speed Relay, or KR20A Cooling Fan Medium Speed Relay.

Static Test

1. Ignition OFF, disconnect the KR20F Cooling Fan Relay, KR20D Cooling Fan High Speed Relay, or KR20A Cooling Fan Medium Speed Relay.
2. Measure for 70 to 110 Ω between terminals 85 and 86 of the KR20F Cooling Fan Relay, KR20D Cooling Fan High Speed Relay, or KR20A Cooling Fan Medium Speed Relay

⇒	If the resistance is not within the specified range, replace the appropriate KR20F Cooling Fan Relay, KR20D Cooling Fan High Speed Relay, or KR20A Cooling Fan Medium Speed Relay.

3. Measure for infinite resistance between following terminals of the appropriate KR20F Cooling Fan Relay, KR20D Cooling Fan High Speed Relay, or KR20A Cooling Fan Medium Speed Relay:

•	Terminals 30 and 86

•	Terminals 30 and 87

•	Terminals 30 and 85

•	Terminals 85 and 87

⇒	If continuity is detected, replace the appropriate KR20F Cooling Fan Relay, KR20D Cooling Fan High Speed Relay, or KR20A Cooling Fan Medium Speed Relay.

4. Connect a 20 A fused jumper wire from the positive terminal of the battery to the appropriate KR20F Cooling Fan Relay, KR20D Cooling Fan High Speed Relay, or KR20A Cooling Fan Medium Speed Relay terminal 85. Connect a jumper wire from the negative terminal of the battery to appropriate KR20F Cooling Fan Relay, KR20D Cooling Fan High Speed Relay, or KR20A Cooling Fan Medium Speed Relay terminal 86. Measure for less than 5 Ω between appropriate KR20F Cooling Fan Relay, KR20D Cooling Fan High Speed Relay, or KR20A Cooling Fan Medium Speed Relay terminal 30 and terminal 87.

⇒	If the resistance measures more than 5 Ω, replace the appropriate KR20F Cooling Fan Relay, KR20D Cooling Fan High Speed Relay, or KR20A Cooling Fan Medium Speed Relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.