Unlike old cars, which used a wire to open the throttle, the APP Accelerator Pedal Sensor or Accelerator Pedal Position Sensor is incorporated in modern cars, trucks, and machinery.
The APP sensor indicates to the car’s computer (PCM) the exact position of the accelerator pedal while driving.
The APP Sensor converts the pedal movement into an electronic signal, which opens the Motorized Acceleration Body.
This system provides greater precision, lower fuel consumption, and effective response to engine load demands.
Next, we will study this Sensor and the steps that must be taken into account to perform an accurate diagnosis of the system.
Accelerator Pedal Sensor APP How does it work?
The operation of the sensor is effortless: the accelerator pedal has built-in two signals from two potentiometers that vary the voltage depending on the degree of opening or closing of the pedal.
When the accelerator is depressed, each of the two sensors sends a signal to the PCM computer. This, in turn, processes these two signals and sends a command to the actuator of the electronic throttle body Throttle Butterfly.
The butterfly opens or closes depending on the degree of rotation of the accelerator pedal.
But why are they two signals coming out of the pedal sensor? The answer is for security.
Imagine going around a curve, and the vehicle sends an erratic signal, and you suffer from sudden acceleration.
The PCM must compare these two signals and check that there is no variation between them, thus ensuring that an accident will not occur if any of these two signals should fail.
These voltages range from 0.3 to 4.8 Volts (Theoretically 0 to 5 Volts) with a 5 Volt reference coming from the PCM.
The voltages go inverse from sensor 1 to sensor 2, meaning Sensor 1 goes from 0.3 to 4.8 Volts upwards, while sensor two would go from 4.8 to 0.3 Volts downwards.
Therefore in the APP sensor connector, there are 6 wires:
- Reference signal 1 from PCM 5 Volts, Sensor 1 signal (variable from 0 to 5 Volts) and ground 1.
- Reference signal 2 from PCM 5 Volts, Sensor 2 signal (variable from 5 to 0 Volts) and ground 2.
Sensor App with PWM Signal
For safety reasons, some systems incorporate a mechanism that allows CAN communication with the PCM by PWM, that is, Signal by Pulse Width Modulation.
This additional signal goes to an independent module via the high-speed CAN network.
This provides security to the system since if communication with the sensor module is lost, another module ensures that the signal remains through the CAN network.
APP Sensor Failures Accelerator Pedal Sensor
The accelerator pedal sensor can fail for several reasons. One of the most common is wearing due to exposure to high temperatures due to its location.
Bad driving habits present another type of failure. There was a habit of accelerating the vehicle off to supposedly get fuel into the fuel system, which is fatal for the potentiometers (damage to the circuit and tracks).
The accelerator pedal should never be pressed if the vehicle is not in contact or the engine is running.
When the sensor fails, a diagnosis is necessary mainly with the following tools:
- Automotive Oscilloscope: allows to graph the two sensor signals and also check if there is a significant voltage drop when the accelerator pedal is pressed.
- Automotive Scanner: Allows you to read the fault codes related to the accelerator pedal and check if the PCM Computer has detected an anomaly in the input signal of both sensor 1 and 2.
- Automotive Multimeter: This allows you to trace the reference voltages at the sensor connector, as well as at the computer pins, and also check the wiring if it is isolated and the continuity of the reference voltage, signal, or ground has been lost.