Car Accelerator Pedal Position Sensors Testing & Replacement
Accelerator Pedal Position (APP) Sensor
The ability to smoothly accelerate down the road while using an adequate amount of energy is attributed to the accelerator pedal position (APP) sensor. The APP sensor, which is fixed to the throttle body of the 'electronic throttle control system with intelligence' (ETCSi), monitors the position of the throttle pedal. The AAP sensor is also involved in converting the movement of the accelerator pedal into an electronic signal, which then initiates the opening or closing of the throttle body.
The accelerator position information is transferred to the throttle actuator control (TAC) module and the powertrain control module (PCM). The accelerator position sensor is made up of two individual sensors, with both sensors designed to have individual sensor return wiring. Each sensor has a varying voltage range.
The PCM system receives and processes the electrical signals from the ACC sensors, along with signals from the direct current (DC) motor, which sets the throttle plate through a throttle cable. When the driver presses down on the accelerator pedal, the pressure rotates the throttle plate inside the throttle body, which opens a passage inside this unit to allow for airflow. As the air travels through the throttle passage to the intake manifold, it activates airflow sensors that manipulate the engine control unit and forces fuel into the fluid injector system.
Waveform notes
In this example, the Accelerator Pedal Position (APP) sensor is of the potentiometer type. It receives two reference voltages from the Powertrain Control Module (PCM), having two ground wires and two signal wires that send a varying voltage back to the PCM relating to accelerator pedal position. The signal voltage sent back to the PCM may vary from manufacturer to manufacturer but will probably never be greater than 5 volts.
Sources and Further Reading
The accelerator position information is transferred to the throttle actuator control (TAC) module and the powertrain control module (PCM). The accelerator position sensor is made up of two individual sensors, with both sensors designed to have individual sensor return wiring. Each sensor has a varying voltage range.
The PCM system receives and processes the electrical signals from the ACC sensors, along with signals from the direct current (DC) motor, which sets the throttle plate through a throttle cable. When the driver presses down on the accelerator pedal, the pressure rotates the throttle plate inside the throttle body, which opens a passage inside this unit to allow for airflow. As the air travels through the throttle passage to the intake manifold, it activates airflow sensors that manipulate the engine control unit and forces fuel into the fluid injector system.
How to perform the test
- Use the vehicle circuit diagram to identify the two signal circuits from the sensor.
- Connect PicoScope Channel A. and Channel B. to the signal circuits.
- Minimize the help page. You will see that PicoScope has displayed an example waveform and is preset to capture your waveform.
- Switch the ignition to ON engine OFF.
- Start the scope to see live data.
- Operate the throttle pedal.
- With your waveforms on screen stop the scope.
- Turn off the ignition.
- Use the Waveform Buffer, Zoom and Measurements tools to examine your waveform.
Waveform notes
Sources and Further Reading
- Grainger R. (2008). Mazda MX-5 Miata 1.8: Enthusiast Workshop Manual. UK, Dorset: Veloce Publishing.
- Erjavec J. (2010). Automotive Technology: A Systems Approach. USA, New York: Delmar Cengage Learning.
- Pickerill K. (2010). Automotive Engine Performance. USA, New York: Delmar, Cengage Learning.
- Hatch ST. (2012). Computerized Engine Controls. USA, New York: Delmar, Cengage Learning.
- “Choosing the Right Automotive Sensor for Throttle Control” - ElectronicDesign
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