Accelerator Pedal Sensor – APP Sensor – How Do Your Voltages Work?

Unlike old cars, which used a wire to open the throttle valve, in modern cars, trucks and machinery, the APP Accelerator Pedal Sensor or Accelerator Pedal Position Sensor is incorporated.

The APP Sensor tells the car’s computer (PCM) the exact position of the accelerator pedal while driving.

For this, the APP Sensor converts the movement of the pedal into an electronic signal, which gives way to the opening of the Motorized Throttle Body.

This system provides greater precision, lower fuel consumption, and an effective response to engine load demands.

Next, we are going to study this Sensor and the steps that must be taken into account to carry out an accurate diagnosis of the system.

Accelerator Pedal Sensor APP How does it work?

The operation of the sensor is very simple: the accelerator pedal has incorporated two signals from two potentiometers that vary the voltage depending on the degree of opening or closing of the pedal.

APP Sensor Potentiometer

When the accelerator is pressed, each of the two sensors sends a signal to the PCM computer, which in turn processes these two signals and sends an order to the electronic throttle body actuator, or Throttle Body.

The butterfly opens or closes depending on the degree of rotation of the accelerator pedal.

But why are there two signals coming out of the pedal sensor? The answer is for security.

Imagine that you are going around a curve and the vehicle sends an erratic signal and you suffer from a sudden acceleration.

The PCM must compare these two signals and verify that there is no variation between them, thus ensuring that if any of these two signals fail, an accident does not occur.

These voltages range from 0.3 to 4.8 Volts (in theory 0 to 5 Volts) with a reference 5 Volts coming from the PCM.

sensor signal app1 and app2
Sensor signal APP1 and APP2 from 0 to 5 Volt

The voltages go in reverse from sensor 1 to sensor 2, meaning Sensor 1 goes from 0.3 to 4.8 Volts up, while sensor two would go from 4.8 to 0.3 Volts down.

Therefore in the APP sensor connector there are 6 wires:

  • Reference signal 1 from PCM 5 Volts, Sensor Signal 1 (variable from 0 to 5 Volts) and ground 1.
  • Reference signal 2 from PCM 5 Volts, Sensor Signal 2 (variable from 5 to 0 Volts) and ground 2.
app sensor pedal six wires
APP Sensor Connector

Sensor App con SeƱal PWM

In some systems, for safety reasons, a mechanism is incorporated that allows CAN communication with the PCM by PWM, that is, Pulse Width Modulation Signal.

This additional signal goes to a separate module via the high-speed CAN network.

This provides security to the system since in the event that communication with the sensor module is lost, another module ensures that the signal remains through the CAN network.

APP Sensor Faults Accelerator Pedal Sensor

The accelerator pedal sensor can fail for a variety of reasons. One of the most common is wear from exposure to high temperatures, due to its location.

Another type of failure occurs due to bad driving habits, since there was a habit of accelerating the vehicle off to supposedly enter fuel into the supply system, and this is fatal for the potentiometers (damage to the circuit and the tracks).

The accelerator pedal should never be pressed if the vehicle is not in contact or the engine is not running.

When the sensor fails, a diagnosis is necessary mainly with the following tools:

  • Automotive Oscilloscope: It allows graphing the two sensor signals and also checking if there is a significant voltage drop when the accelerator pedal is pressed.
  • Scanner Automotriz: Allows you to read the fault codes related to the accelerator pedal and check if the PCM Computer has detected an abnormality in the input signal of both sensor 1 and 2.
  • Automotive Multimeter: allows you to trace the reference voltages at the sensor connector as well as the computer pins, and also check the wiring if it is isolated and continuity of reference voltage, signal or ground has been lost.

If you have problems with detecting this type of failure, or the procedures to repair damage to automotive sensors, we invite you to participate in the automotive sensors course, and the automotive scanner driving course.

This way we increase your diagnoses and therefore you will get better results in your automotive workshop.