How the accelerator pedal sensor works
Accelerator pedal sensor
Here you will find useful basic information and important tips relating to the accelerator pedal sensor/pedal value transmitter in vehicles.
The accelerator pedal sensor transmits the position of the accelerator pedal to the engine control unit. Based on this information, the load requested by the driver can be implemented immediately. On this page we will explain the principle according to which modern pedal travel transmitters operate, and which symptoms indicate a fault in this sensor. You will also find out how accelerator pedal sensors are checked in the workshop.
Important safety note
The following technical information and practical tips have been compiled by HELLA in order to provide professional support to vehicle workshops in their day-to-day work. The information provided on this website is intended for suitably qualified personnel only.
TABLE OF CONTENTS
HOW THE ACCELERATOR PEDAL SENSOR WORKS: FUNCTIONAL PRINCIPLE
Modern vehicles are being equipped with an ever-increasing number of electronic components. Among other things, this is due to legal regulations, e.g. those governing a reduction in emissions and fuel consumption. Electronic components are also increasingly being used to increase active and passive safety as well as driving comfort. One of the most important components is the accelerator pedal sensor.
When it comes to automotive applications, a non-contact sensor based on an inductive principle is increasingly being used. This sensor comprises a stator (which includes an excitation coil, receiver coils, and an electronic evaluation unit) and a rotor (formed of one or more closed conductive loops with a certain geometry).
The application of alternating voltage to the transmission coil produces a magnetic field which induces voltages in the receiver coils. A current is also induced in the rotor conductive loops which, in turn, influences the magnetic field of the receiver coils. Voltage amplitudes are produced depending on the position of the rotor relative to the receiver coils in the stator. These are processed in an electronic evaluation unit and then transmitted to the control unit in the form of direct-current voltage. This evaluates the signal and forwards on the relevant pulse, e.g. to the throttle valve actuator. The characteristics of the voltage signal depend on how the accelerator pedal has been pressed.
Accelerator pedal sensor (pedal value transmitter)
Design of accelerator pedal sensor (pedal value transmitter)
SYMPTOMS OF A FAULTY ACCELERATOR PEDAL SENSOR: SYMPTOMS
If the accelerator pedal sensor fails, the following fault symptoms may occur:
- Increased engine idling speed
- Vehicle does not respond if the accelerator pedal is pressed
- Vehicle switches to "limp-home mode"
- Engine warning light in the cockpit illuminates
ACCELERATOR PEDAL SENSOR FAULTY: CAUSE OF FAILURE
A failure could have a number of different causes:
- Damaged cables or connections on the accelerator pedal sensor
- Missing voltage and ground supply
- Faulty electronic evaluation unit in the sensor
CHECKING THE ACCELERATOR PEDAL SENSOR: TROUBLESHOOTING
The following test steps should be considered during troubleshooting:
- Read out fault code
- Visual inspection of the accelerator pedal sensor to check for mechanical damage
- Visual inspection of the relevant electrical connections and cables to ensure they are properly fitted and for any damage
- Check of the sensor using an oscilloscope and multimeter
Using the example of a MB A-Class (150) 1.7, the following test steps, technical data, and figures are listed to explain the troubleshooting work.
| Control unit pin | Signal | Test conditions | Reference value |
|---|---|---|---|
| C5 blue-yellow | → | Acceleration off | 0V |
| C5 | → | Acceleration off | 4.5 – 5.5 V |
| C8 violet-yellow | ⊥ | Acceleration on | 0V |
| C blue-grey | ← | Acceleration on, accelerator pedal released | 0.15V |
| C9 | ← | Acceleration on, accelerator pedal pressed | 2.3V |
| C10 violet-green | ← | Acceleration on, accelerator pedal released | C10 |
| ← | Acceleration on, accelerator pedal pressed | 4.66V | |
| C23 brown-white | ⊥ | Acceleration on | 0V |
→ output signal ← input signal ⊥ control unit ground
RECOMMENDATION!
The measurements should be performed by two people. The work involved in capturing the signals on the sensor, carrying out various test cycles, and performing diagnostics work on the oscilloscope is difficult for a single person to handle, and it will take them much longer to complete this work.
Accelerator Pedal Training
In this video, we will show you the technologies of the accelerator pedals, how they work and discuss the faults. In addition, we will show the diagnosis of the element? using mega macs and tell you what to look for.
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