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When monitoring vehicle data via OBDII port, I see that i have accelerator pedal position D and E. What are these and can I calculate overall pedal position from them? Thank you

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Inside your Accelerator Pedal Position Sensor, you actually have two or more separate sensors which the ECU uses to validate the integrity of the signals. These both are fed two different voltage sources (one sensor (sensor E) gets half the input voltage compared to D, causing half the output voltage) by the ECU as a fail-safe.

From my research. Most Accelerator Pedal Position Sensors use an incremental voltage value when the pedal is applied (same as a throttle position sensor, more press = higher voltage to ecu).

Because of this, the ECU knows the incremental voltage of Sensor E should always represents half of the Sensor D voltage. In most vehicles, the corresponding algorithms are as follows: Sensor E X 2 = Sensor D. For illustration purposes: if Sensor E displays a reading of 1.5 volts, the Sensor D reading should be approximately 3 volts, with a variance of more or less 50 mV.

This allows the ECU to know if a fault has occurred in the Accelerator Position Sensor circuit.

If one sensor fails, the ECU will now see a greater than 50mV (seems like above 100mV is the cutoff) difference between the two sensors. When the ECU sees this, it knows that these sensors are both in the same spot so should be identical, this means something is wrong, and because this car is a drive-by-wire throttle system, the ECU will activate a limp-mode of sorts for safety and throw some Diagnostic Trouble Codes so the driver knows something is wrong.

I'm not certain in your data-logger which will show 100% when foot to the floor and which will show 50%, so you can probably just try putting your foot to the floor and see which one maxes out. Seems like D should be the real position, however test first.

Note: This is only your accelerator pedal position, your ECU (engine control unit) command a different throttle position based on driving modes (sport, soft etc) and various other conditions, so you may find the throttle position (Relative throttle position) useful. Relative will show a 0-100 I believe, the Absolute will show 0-100 including the idle holding the throttle plate open slightly, though this depends on engine design.

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most accelerator pedals have two sensors inside. Newer cars uses hall type sensors and older uses resistance type sensors.

Normally these two sensor will show opposite signal to each other. Thats the cars way of detecting fault in the signal.

Maybe "D" and "E" are these two signals? Do you have a screenshot from the OBD reader?

  • Hi Phingoc, thank you for the reply. I have updated my post with an image of the data. – Young4844 Jun 12 at 16:19

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