Accelerator Pedal Module

Accelerator Pedal Module

The accelerator pedal module detects the driver's instructions for altering the speed of the vehicle.

Design and function
The position of the accelerator is detected by a special sensor and analyzed by the digital engine module (DME). The accelerator module is fitted with two independent Hall-effect sensors. Those sensors each transmit a voltage signal corresponding to the current pedal position. For safety reasons, two sensors are used. On that basis and taking other engine operating parameters into account, the required position for the throttle valve is calculated. The throttle valve is then operated by the throttle valve positioner.
The accelerator module receives a constant voltage of 5 V from the DME. For safety reasons, each sensor has a separate power supply.
The two Hall-effect sensors transmit a signal that is proportional to the pedal position. The signal from sensor 2 is always exactly half the voltage of the signal from sensor 1. The two signal voltages are permanently monitored by the DME.

Diagnosis
The maximum engine output is limited in the event of a fault. The vehicle has a delayed response to abrupt movements of the accelerator pedal. If two faults occur simultaneously, the engine speed is limited to max. 1500 rpm. The relevant fault codes are stored on the DME identifying the faulty Hall-effect sensor.

The following faults can be detected:
- Hall-effect sensor short circuit
- Signal above Hall-effect sensor voltage range
- Signal below Hall-effect sensor voltage range
- Implausible difference between signal levels of the two Hall-effect sensors
- Power supply failure or voltage too low