This function is used to activate the retarder's PWM-valve so that 25%, 50%, 75%, and 100% of max. pressure is reached. If the pressure is outside limit values, it may be due to the pressure in the trailer being too low, the retarder's PWM-valve has failed, or that there is a leak in the retarder.
Test conditions:
engine off, ignition on.
Parking brake applied.
Air pressure in transmission between 650 and 1,000 kPa.
Battery voltage above 20V.
Procedure:
Start the function.
Check test conditions.
Check that the current value for each level is between the min. and max. value.
The function is done.
If the function fails, check the test conditions and repair any faults.