• | 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. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
Relay Coil Ignition Circuit | P0480, P0481 | P0480, P0481 | -- | -- |
Relay Switch Ignition Circuit | 1 | 1 | -- | -- |
Fan Low Control Circuit | P0480 | P0480 | P0480 | -- |
Fan High or Fan Control Circuit | P0481 | P0481 | P0481 | -- |
Relay Controlled Output Circuit | 1 | 1 | 2 | -- |
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The engine control module (ECM) commands the fans 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 engine is running. |
• | The ignition voltage is between 11-18 volts. |
• | The engine speed is greater 400 RPM. |
• | The DTCs run continuously once the above conditions are met. |
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 seconds.
DTC P0480 and P0481 are Type B DTCs.
DTC P0480 and P0481 are Type B DTCs.
Cooling System Description and Operation
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Control Module References for scan tool information
⇒ | 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. |
⇒ | If the test lamp is always ON, test the relay coil control circuit for a short to ground. If the circuit tests normal, replace the 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 ECM. |
⇒ | If the resistance is not within the specified range, replace the relay. |
• | 30 and 86 |
• | 30 and 87 |
• | 30 and 85 |
• | 85 and 87 |
⇒ | If not the specified range, replace the relay. |
⇒ | If greater than the specified range, replace the relay. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for ECM replacement, setup, and programming |