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 Descriptor
DTC P1482: Cooling Fan Speed Output CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Cooling Fan Speed Control | P1482 | P1482 | P1482 | -- |
Cooling Fan Motor Supply Voltage | -- | -- | -- | -- |
Cooling Fan Low Reference | -- | -- | -- | -- |
Battery Positive Voltage | -- | -- | -- | -- |
Ground | -- | -- | -- | -- |
Circuit/System Description
The engine cooling fan is a variable speed fan. The engine control module (ECM) controls the fan speed by sending a pulse width modulated signal to the cooling fan speed control module. The cooling fan control module varies the voltage drop across the engine cooling fan motor in relation to the pulse width modulated signal. The cooling fan speed is affected by many different conditions and can be adjusted from 10 to 84 percent duty cycle (PWM). A duty cycle of 84 percent is considered high fan speed. When multiple cooling speed requests are received the ECM uses the highest cooling fan speed of all the requests. During normal fan ON operation the control circuit voltage will be low and near battery voltage when the fan is OFF.
Conditions for Running the DTC
| • | The battery voltage is between 9-18 volts. |
| • | The engine speed is greater than 400 RPM. |
Conditions for Setting the DTC
| • | The commanded state of the output driver module (ODM) and the actual state of the control circuit do not match. |
| • | The condition is present for more than 5 seconds. |
Action Taken When the DTC Sets
DTCs P1482 is Type B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P1482 is Type B DTCs.
Diagnostic Aids
- Cooling fan duty cycle starts when engine coolant temperature reaches approximately 95°C (204°F) and reaches high speed at temperatures above 113°C (235°F).
- Cooling fan duty cycle starts when A/C pressure reaches approximately 1100 kPa (160 Psi) and reaches high speed at A/C pressures above 2480 kPa (360 psi).
- At engine oil temperatures above approximately 150°C (302°F) the cooling fan duty cycle will be commanded to high speed.
- At transmission oil temperatures above approximately 132°C (270°F) the cooling fan duty cycle will be commanded to high speed.
- After the vehicle is shut OFF if the engine coolant temperature at key-off is greater than 113°C (235°F) or the A/C pressure is greater than 1720 kPa (249 psi) the cooling fan duty cycle is set to 50 percent, low speed. If the coolant temperature drops below 110°C (230°F) and the A/C pressure drops below 1660 kPa (241 psi) the fan will shut OFF. The fans will automatically shut OFF after 2 min. regardless of coolant temperature.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Cooling Fan Description and Operation
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Ignition ON, increase and decrease the cooling fan ON and OFF with a scan tool. Observe that the cooling fan operates with each command.
- Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
Important: Circuit/System Verification must be performed first or misdiagnosis may result.
- Ignition OFF, disconnect the engine harness connector from the cooling fan speed control module.
- Ignition OFF, install a test lamp between the cooling fan speed control circuit terminal X3 49 and B+. The lamp should be OFF.
- Ignition ON, command the cooling fan ON with a scan tool. The lamp should be ON.
- Ignition OFF, disconnect the cooling fan harness connector at the cooling fan speed control module.
- Connect a jumper wire between the fan ground circuit terminal 1 and ground. Connect a 30A fused jumper wire between the positive terminal at the battery and the fan voltage supply circuit terminal 4 and verify fan activation.
- Ignition OFF, measure between the cooling fan speed control module ground circuit terminal 2 at the harness connector and ground for less than 1 ohm.
- Install appropriately fused jumpers in the power and ground circuits between the cooling fan speed control module harness connector terminals and the cooling fan harness connector terminals. The fan should activate at full speed.
- If the ECM, fan, and all circuits test normal, replace the cooling fan speed control module.
| ⇒ | If the lamp is ON, test the cooling fan speed control circuit for a short to ground. If the circuit tests normal, replace the ECM. |
| ⇒ | If the lamp is OFF, test the cooling fan speed control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM. |
| ⇒ | If the cooling fan does not activate, replace the cooling fan. |
| ⇒ | If the fan does not activate correctly, test the cooling fan speed control module voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and its fuse is open, replace the cooling fan speed control module. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for ECM replacement, setup, and programming
