P0495
DTC P0495 (LGH/LML)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
DTC Descriptor
DTC P0495
- Cooling Fan Speed High
Diagnostic Fault Information
Circuit/System Description
The cooling fan relay sends a pulse width modulated (PWM) signal of 12-14 volts to the cooling fan clutch through the cooling fan clutch solenoid voltage control circuit. The cooling fan relay varies the voltage drop across the cooling fan clutch solenoid in relation to a pulse width modulated signal from the ECM in order to control the speed of the cooling fan. The signal controls the position of the oil control valve inside the cooling fan clutch housing.
Conditions for Running the DTC
* DTC P0016, P0112, P0113, P0117, P0118, P0335, P0336, P0340, P0341, P0480, P0483, P0526, P2228, or P2229 is not set.
* The engine is operating for greater than 10 seconds.
* The engine speed is greater than 1,181 RPM.
* The engine OFF time after the previous ignition cycle was greater than 0 seconds.
* The ambient air temperature (AAT) is warmer than -40°C (-40°F).
* The BARO is greater than 55 kPa.
* The ECM commanded fan duty cycle is less than 45 percent.
* DTC P0495 runs continuously when the conditions above exist.
Conditions for Setting the DTC
* The cooling fan speed is greater than 1,500 RPM for 80 seconds.
OR
* The clutch fluid pump-out, which is the time it takes for the fan clutch to disengage completely, is greater than a range of 10 minutes at sea level to 52 minutes at elevations of 6,500 ft.
Action Taken When the DTC Sets
DTC P0495 is a Type B DTC.
Conditions for Clearing the DTC
DTC P0495 is a Type B DTC.
Reference Information
Schematic Reference
Engine Cooling Schematics (Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
Cooling Fan Description and Operation (Gas) (Description and Operation)Cooling Fan Description and Operation (Diesel) ()
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference
Control Module References (Control Module References) for scan tool information
Circuit/System Verification
1. Ignition OFF, verify the fan clutch is not seized or binding.
2. Ignition ON, observe the DTC information with a scan tool. Verify DTC P0480, P0483, or P0526 is not set, if a DTC is set diagnose that DTC first.
3. Engine idling at operating temperature with all accessories turned OFF, for greater than 10 minutes.
Note: Depending on elevation above sea level it may take up to 52 minutes for the fan clutch to completely disengage.
4. Observe the scan tool DTC information. Verify DTC P0495 is not set.
• If the DTC is set, replace the cooling fan clutch assembly.
5. Operate the engine at 1,500 RPM for 2 minutes. Observe the DTC information with a scan tool. Verify DTC P0495 is not set.
• If the DTC is set, replace the cooling fan clutch assembly.
6. 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 fan clutch harness connector X142.
2. Connect a test lamp between the cooling fan clutch solenoid voltage control circuit terminal B and ground.
Note: Ensure that the test lamp and harness connector are positioned away from the cooling fan, drive belt, and pulleys.
3. Engine operating, command the fan clutch relay to 50 % with a scan tool. The test lamp should illuminate and flash ON and OFF.
• If the test lamp illuminates without flashing, test the solenoid voltage control circuit for a short to voltage. If the circuit tests normal, replace the fan clutch relay.
4. If all the circuit/connections test normal, test or replace the cooling fan clutch assembly.
Component Testing
Relay Test
1. Remove the cooling fan clutch relay.
2. Connect a 10 A fused jumper wire between relay terminal 2 and B+. Connect a jumper wire between relay terminal 6 and ground.
3. Test for less than 1 V between terminal 4 and ground.
• If greater than the specified value, replace the fan relay.
4. Connect a jumper wire between terminal 5 and ground.
5. Test for B+ between terminal 4 and ground.
• If less than the specified value, replace the fan relay.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Fan Clutch Replacement (Diesel) ()
* Control Module References (Control Module References) for ECM replacement, setup, and programming