Some vehicles may exhibit DTC P0481 (Cooling fan relays malfunction) stored
in the PCM.
The false DTC detection occurs when the A/C refrigerant pressure switch is ON
but the cooling fan relay is turned OFF by the PCM because the coolant
temperature is 108°C degrees and under. The PCM stores DTC P0481 because the
cooling fan is operating without PCM control command. This is due to improper
Customers having this concern should have their vehicle repaired using the
- Confirm the cooling fan is operating normally by activating the cooling
fan relays using either one of the following methods.
- Connect DLC terminals TEN and GND with a jumper wire and open the
throttle valve with the ignition switch ON.
- Activate the simulation function on the NGS tester with either the
ignition switch ON and engine off, or during idle. Select the "FAN1", "FAN2"
or "FAN3" PID for the cooling fan relay.
- Using WDS (Version B22NM or later), reprogram the PCM to the latest
calibration. Use the table below to confirm the correct calibration:
- It is not necessary to remove any fuses or relays during PCM
reprogramming when the WDS screen prompts you to do so. You may accidentally
stop power to one of the PCM terminals and cause the PCM to be blanked or
you may receive error messages during the WDS reprogramming procedure.
- WDS shows the calibration part number after programming the PCM.
- Please be aware that PCM calibration part numbers and file names listed
in any Service Bulletin may change due to future releases of WDS software
and additional revisions made to those calibrations for service related
concerns. When reprogramming a PCM, WDS will always display the "latest"
calibration P/N available for that vehicle. If any calibration has been
revised/updated to contain new information for a new service concern/issue,
it will also contain all previously released calibrations.
- When performing this procedure, if the WDS PTU is not docked and
connected to 115V-120V, we recommend that a battery charger be installed on
the vehicle battery and turned ON to a maximum charge of no more than 20
AMPS to keep the vehicle battery up to capacity. If you exceed 20 AMPS it
will damage the WDS PTU.
|PCM Calibration Part Number
- Install revised PCM calibration sticker in the appropriate position (next
to vehicle emissions label) with the calibration P/N provided in the table
- Road test the vehicle to relearn the "Keep Alive Memory" (KAM) strategy.
- Verify repair.
Note: This information applies to verified customer complaints on vehicles covered under normal warranty.
Refer to the SRT microfiche for warranty term information.
|Part Number Main Cause