This function is used to check that signals from the control for the retarder are received and interpreted correctly by the control unit. A value is shown for every position that the control may assume. The signal from accelerator pedal position and brake pedal switch are also shown, these control when the retarder shall or can be activated. Also shown is the offset above selected speed on the cruise control that the trailer is not permitted to pass during retardation.
If any signal is incorrect, this indicates a fault in the circuit between the control and VECU or defective control.
Accelerator pedal position: Check that the displayed value in percent matches the actual position of the pedal. When the accelerator pedal position exceeds 1%, the auxiliary brake cannot be activated.
Retarder's offset speed: The auxiliary brakes are activated if the trailer speed exceeds the cruise control's requested speed by the value of the offset. This value is adjusted with active cruise control.
Control, auxiliary brake, position: The signal should change when the position of the control changes.
Brake pedal switch: Check that status of the brake pedal switch matches the pedal's actual position. This signal activates the auxiliary brake when the control is in position A.
Control, auxiliary brake +: The signal should change when the position of the control changes.
Control, auxiliary brake -: The signal should change when the position of the control changes.
Test conditions:
Ignition on.
Procedure:
Start the test.
Check that status of the controls matches the test.
Finish by pressing "OK".
The function is done.