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Pedal position sensor

Pedal position sensor


The accelerator is connected by a standard cable to two pedal position sensors located in the throttle body.

The sensors are placed in the throttle body because the throttle cable can then easily be connected to the throttle valve spindle if a fault occurs in the throttle control system.

The pedal position sensors consist of two potentiometers which are supplied with 5 V from control module pins 69 and 46, which are connected together internally in the throttle body. The sensors are grounded via control module pins 22 and 70, which are also connected internally in the throttle body.

The voltage from sensor 1 is applied to control module pin 56 and decreases as the pedal is depressed.

The voltage from sensor 2 is applied to control module pin 9 and increases as the pedal is depressed.

The aggregate voltage from the two sensors is always about 5 V. If the total differs too widely from 5 V, a fault must have occurred in one of the potentiometers or their circuits.

The system enables the pedal position to be determined with a high degree of accuracy.

The control module uses the value from sensor 1 as an indicator of the driver's torque request. The value is converted into requested mass air flow/consumption and constitutes the most important input signal for mass air flow control.

When the pedal is fully released, the control module adapts the voltage from sensor 1. When the accelerator is fully released, the mass air flow/consumption required = 0 and if the car speed = 0 also, the idle speed control will be activated.

Diagnostics


If the aggregate voltage from the two pedal sensors differs too widely from 5 V, a fault must have occurred in one of the potentiometers or their circuits. The pedal position is not therefore reliable.

Diagnostic trouble code P1530 or P1531 will be generated if the throttle valve control goes into limp-home mode.

If the voltages from the two pedal position sensors are shorted to each other, the pedal sensor voltage will be 2.5 V irrespective of the pedal position, which corresponds to a pedal pressed half-way down. This fault is not covered by the total voltage check and therefore the control module sends out short pulses on the input for sensor 2. If these pulses are detected on the input for sensor 1, a short-circuit has occurred between the sensors.

Diagnostic trouble code P1532 is generated and the throttle valve control goes into limp-home mode.



Note

• If a pedal position sensor fault occurs, maximum engine speed is limited to 2200 rpm through fuel shut-off.

• Pedal sensitivity is not changed in limp-home mode.