Camshaft Position Sensor : Working, Types, Testing & Its Applications

Nowadays, automobile sensors have become very significant over the years which help in monitoring different problems of cars & send the information to the Electronic Control Unit (ECU) or car driver. The ECU in certain situations makes some adjustments to the specific component depending on the information obtained from the automobile sensor. Generally, sensors in automobiles monitor various aspects like temperature, engine condition, coolant system, pressure of oil, vehicle speed, levels of emission, etc. There are different types of sensors used in automobiles like airflow, engine knock, engine speed, voltage, oxygen, throttle position, camshaft position sensor, MAP, airbag, car parking, crankshaft position sensor, etc. This article discusses an overview of the camshaft position sensor, its working, and its applications.

What is Camshaft Position Sensor?

An automobile sensor that is used in a car engine to measure the position & rotation of the camshaft & sends the information to the engine control module of the vehicle is known as a camshaft position sensor. This sensor is also known as a phase detector or cylinder identification sensor. It is a very small & very significant magnetic device in every current automobile because it ensures that the car engine is working correctly or not.

This sensor is arranged near the car engine and it can be found behind the head of the cylinder or in the lifter valley of the vehicle. The camshaft position sensor is located normally on eight-valve engines in the cylinder head end whereas it is arranged on the cylinder head of sixteen-valve engines. The camshaft position sensor diagram is shown below.

Camshaft Position Sensor
Camshaft Position Sensor

Working Principle

The working principle of the camshaft position sensor mainly depends on the Hall Effect sensor or optical sensor for detecting the revolution of the camshaft. The Hall Effect sensor detects the revolution by using the magnetic field whereas the optical sensor detects the position of the camshaft by using a light beam. The camshaft position sensor is normally a Hall Effect or magnetic sensor. So it works simply by detecting the way of an iron gear connected to the camshaft when it turns. Once the gear passes the sensor then it produces a signal and transmitted it to the ECU. After that, the ECU uses this data to adjust the fuel injection timing & ignition systems.

If this sensor does not work properly then it reduces the working performance of the engine, reduces fuel efficiency, and increases emissions. A faulty camshaft position sensor can cause the engine to misfire and injure so it can be very hazardous while driving.


Its primary function is to provide the engine control module (ECM) or engine control unit (ECU) with accurate information about the position and speed of the camshaft. This information is essential for the proper operation of the engine and various related systems. Here are the key functions of a camshaft position sensor:


Determining Camshaft Position:

  • The main function of the camshaft position sensor is to determine the precise position of the camshaft as it rotates. This information helps the engine control module (ECM) synchronize the opening and closing of the engine’s intake and exhaust valves with the corresponding positions of the pistons. Proper valve timing is crucial for efficient combustion and engine performance.

Optimizing Fuel Injection Timing:

  • By accurately detecting the camshaft’s position, the CMP sensor assists the ECM in determining the optimal timing for fuel injection. This ensures that the right amount of fuel is injected into the combustion chamber at the right moment, enhancing fuel efficiency and reducing emissions.

Coordinating Ignition Timing:

  • The camshaft position sensor also plays a role in coordinating ignition timing. The ECM uses the camshaft position information to determine when to trigger the spark plug ignition, ensuring that combustion happens at the correct moment in the engine’s cycle.

Detecting Misfires:

  • A malfunctioning camshaft position sensor can lead to misfires, where fuel isn’t ignited properly in one or more cylinders. The sensor’s data helps the ECM identify and diagnose these misfires, allowing the system to take corrective action.

Enabling Variable Valve Timing (VVT):

  • In engines equipped with variable valve timing systems, the camshaft position sensor helps control the timing of valve opening and closing. This can optimize engine performance, power, and fuel efficiency across different operating conditions.

Managing Engine Performance:

  • The ECM uses the camshaft position data to monitor and adjust various engine parameters, including air-fuel mixture, valve timing, and ignition timing. This ensures the engine operates efficiently and meets emission standards.

Supporting Engine Safety:

  • In some cases, a faulty camshaft position sensor can trigger the engine control module to enter a “safe mode” to prevent potential damage. This can involve limiting engine power to protect critical components.

Diagnosing Engine Issues:

  • The camshaft position sensor contributes to onboard diagnostics (OBD) by providing valuable data that can be used to identify engine performance issues and malfunctions. This data can be read using diagnostic tools to troubleshoot problems.

Types of Camshaft Position Sensors

There are three types of camshaft position sensors available magnetic type, hall effect, and AC output which are discussed below.

Magnetic Type Sensor

This type of camshaft position sensor is identified simply through the two wires. This sensor generates its own voltage, an AC sine wave signal. This sensor can be arranged within the distributor or above the camshaft. When this sensor is close to the camshaft which has a permanent magnet device connected to it then every time the magnet will pass through the sensor and generates a magnetic field & the resulting pulse can be transmitted to the ECM for further processing.

Magnetic Type Camshaft Position Sensor
Magnetic Type Camshaft Position Sensor

Hall Effect Camshaft Sensor

This kind of camshaft sensor includes three wires where the first wire is used for power, the next wire is for GND and the last wire is for the voltage signal to be sent to the PC. This sensor is arranged on the camshaft or in the distributor. This sensor has a screen through a slot & a magnet placed above the shaft. Once the screen of this sensor moves in between the sensor & magnet, then this sensor will be turned ON & OFF. If this screen has a solid area ahead of the sensor, then feedback voltage can be disrupted as the magnetic field splits.

Hall Effect Camshaft Sensor
Hall Effect Camshaft Sensor

AC Output Sensor

AC output sensor is a special kind of sensor used to produce an AC voltage signal like an output. The engine control module in the car produces extremely high frequency for the exciter coil and which is arranged close to the rotary disc.

This rotary disc is arranged on the camshaft’s end & it has a slit with it. Once this slot passes through the coil then it will be excited by mutual induction and a signal indicating the first cylinder position is transmitted to the engine control module. These types of sensors are frequently observed within Vauxhall ecoTEC engines.

AC Output Sensor Type Sensor
AC Output Sensor Type Sensor

Camshaft Position Sensor Wiring Diagram

The camshaft position sensor is generally used to place the position of the camshaft engine & change it into an electronic signal after that it sends to the ECU of the car. This sensor position is available with different wiring diagrams like two wires and three wires. The wiring diagram of the three-wire camshaft position sensor is shown below.

Camshaft Position Sensor Wiring
Camshaft Position Sensor Wiring

The 3-wire camshaft position sensor includes three wires; reference voltage wire, signal wire, and ground. These three wires are simply connected to the Electronic Control Unit. This sensor gets a power source from the ECU, the GND of this sensor is taken from the Electronic Control Unit & finally, the voltage signal wire goes from the camshaft sensor to the Electronic Control Unit.

A three-wire camshaft sensor has a magnet & a steel material such as germanium & a transistor. Once an object approaches very near to this sensor, then its magnetic flux will be changed thus, voltage is generated within the material and is amplified through the transistor & transmitted to the ECU.

Camshaft Position Sensor Interface with Microcontroller ( Arduino or PIC):

There are different types of camshaft sensor available as we saw above. Each comes with its own types of output. While interfacing a camshaft sensor with the microcontroller following points need to be considered.

  1. Understand the Sensor Output:

                       Determine the type of signal your camshaft position sensor produces. It could be a digital signal (ON/OFF), analog voltage, or PWM (Pulse Width Modulation) signal. In case of

  • Halleffect Sensors:
      • Output Type is: Digital
      • Description: Hall Effect sensors detect changes in a magnetic field. They typically provide a digital signal that switches between HIGH and LOW states as the camshaft rotates, indicating the position of the camshaft.
  • Optical Sensors:
      • Output Type is : Digital (usually)
      • Description: Optical sensors use light to detect the position of the camshaft. They often provide a digital signal with pulses that represent the camshaft’s position.
  • Magnetic Sensors (Variable Reluctance Sensors):
      • Output Type: Variable (analog-like)
      • Description: Magnetic sensors generate an analog-like voltage signal that varies as the camshaft rotates. The signal’s amplitude changes with the camshaft position.

2.  Choose Input Pins:

               On the  microcontroller, select the digital or analog pins that you will use to connect to the camshaft position sensor. Make sure these pins are compatible with the sensor’s output signal and     voltage levels.

  1. Wiring:    Connect the camshaft position sensor’s output to the chosen input pins on the microcontroller. Use appropriate voltage dividers or level shifters if needed to ensure the sensor’s voltage levels are compatible with the microcontroller.
  1. Power Supply:  Provide the necessary power supply to the camshaft position sensor. This might involve connecting the sensor to a suitable voltage source (e.g., 5V) and connecting its ground (GND) to the microcontroller’s ground.
  1. Read the Sensor Data: Write code in the programming language supported by your microcontroller (e.g., C/C++, Python, etc.) to read the signal from the sensor. Use digitalRead() or analogRead() functions as needed.

     6. Processing the Data: Depending on the sensor type, you might need to process the sensor data further. For example, if you’re using a digital sensor, you might directly use its state for your            application. If you’re using an analog sensor, you may need to convert the analog voltage into a meaningful value.

Camshaft Sensor Interface to Microcontroller Code:

#include< Arduino.h>   

const int sensorPin = 2;  // Replace with the actual pin number

int sensorValue = 0;

void setup() {

  pinMode(sensorPin, INPUT);



void loop() {

  sensorValue = digitalRead(sensorPin);


  delay(1000);  // Delay for 1 second


Camshaft Position Sensor Symptoms

When the camshaft piston sensor malfunctions then a number of issues can occur. So there are some warning symptoms that occur before this sensor has failed completely & the car engine will shut down.

Make Sure the Engine Light is ON

The engine light turns ON if the camshaft position sensor stops working. Once this light is ON then need to stop the vehicle without delay. If you pay no attention to it, then it will cause severe harm to the car engine.

Ignition Issues

Once any problem with the sensor begins, then the signal which is transmitted to the engine of the car also not works. So the transmitted signal is very weak and it will not let the car begin as there will be no flicker from the ignition system.

Fuel Efficiency is Poor

If the vehicle lacks in providing enough fuel for the car engine then the sensor may provide wrong information to the ECM otherwise the fuel injectors could open for a very long time. So this will make the engine not work very efficiently, cause engine knocking & can cause very serious injuries.

Transmission Shifting is Poor

If the camshaft position sensor is wrong then the cars with automatic transmissions will face some problems while changing car gears. So need to turn off your car engine, stay a bit & again start the engine. In addition, the data obtained through the ECM from a bad sensor avoids the shift solenoid from working & shifting car gears which is known as Limp Mode and it helps in protecting the car engine from harm by reducing the speed of the engine.

Stalling of Engine

Once the car engine stalls or stops while driving because of not supplying sufficient fuel to the engine by fuel injectors the engine may get a stall and the car may get damaged.

Fuel Consumption is high

A faulty sensor can affect fuel economy negatively which means the engine of the vehicle consumes more fuel. This problem is very rare although we cannot negligible & needs instant replacement or repair of the sensor.

Poor Acceleration

Poor acceleration occurs because of the bad camshaft position sensor. Once this sensor stops working the vehicle will not accelerate very fast. Once poor acceleration occurs then it causes your car to sputter, lack of power, poor speed, stop or even stall.

Engine Misfire

The sensor signal is necessary to work fuel injectors and engines. If this sensor fails then it can cause the engine to misfire and gives vibrations when it accelerates.

Gas Smell

A faulty sensor can dump unburned fuel indirectly into the exhaust system of a vehicle. So this not only affects the economy of fuel but also causes some black smoke and it causes a clear smell which is extremely unsafe for people.

Rough Idling

The failure of the sensor can cause Rough idling of the vehicle engine. Once the sensor malfunctions, then it occurs because of asynchronous combustion within the cylinder.

How to Test a Camshaft Position Sensor using a Multimeter

Camshaft position sensor testing is very important to check its proper functioning. These sensors can be affected by many malfunctions which can affect the sensor failure or its uneven operation. So an accurate sensor diagnosis is very important testing. Camshaft position sensor testing is possible by using a multimeter or an oscilloscope. So testing a camshaft position sensor with a multimeter is very easy & faster.

To test this sensor using a multimeter, it is essential to measure the sensor voltage that is produced on its signal wire. Here, the data which is obtained mainly depends on the type of sensor and vehicle. In addition, based on the sensor type, they have different pins because an inductive or magnetic type camshaft sensor includes two wires whereas a hall effect type sensor includes three wires..

Before you begin the sensor test using a multimeter, you must set the box in neutral or in a park, locate the car on the parking brake & detach the fuel system by simply pulling the jumper of the fuel pump from the fuse block to avoid engine starting.

3-wire Camshaft Position Sensor Testing

To test three wire camshaft position sensors, you need to set the DC volts mode on the multimeter & separate the connector of the sensor.

  • First, the red color probe of the multimeter need to be connected to the power lead & the black color probe to the minus of the battery;
  • After that for a few seconds, try to start the car engine.
  • Now the voltage reading must be about 5 volts on the multimeter.
  • To observe if the sensor connector minus wire is intact & short-circuited, attach the red dipstick to it & keep the black one above the battery’s negative terminal.
  • Now, need to start the car engine again, the reading of voltage must be 0.1 or 0.2V on the multimeter screen.
  • The same process must be tested by the signal wire only, now the voltage on the multimeter screen should change from 0 – 5 volts if the sensor is good.
  • Now without starting the car engine & only with the ignition on, measure the voltage in between the plus & signal contacts, it should be a minimum of 90% of the voltage supply.

How to Replace Camshaft Sensor?

To replace this sensor, the following steps need to be followed.

  • At first, we have to separate the negative cable of the battery.
  • Need to place this sensor normally on the front, back, or top of the car engine and it will have probably a 2 to 3-wire connector connected.
  • Once you discover it, then you have to discharge the tab above the sensor to separate the wires from the camshaft sensor.
  • Without any delay, take off the mounting bolt which is connected to the camshaft sensor to the car engine.
  • Pull off the exhausted sensor through a small twist.
  • Once a new sensor is connected, you have to apply some engine oil to the O-ring of the sensor.
  • Set up the new sensor and protect it through the mounting bolts.
  • Again connect the wire connector properly to the camshaft sensor.
  • At last, reconnect the battery’s negative terminal.
  • Then, take a test drive to know whether the camshaft position sensor working or not.


The camshaft position sensor uses include the following.

  • The camshaft sensor allows the engine control to decide the precise location of the crankshaft drive.
  • This sensor tracks the rotation of the camshaft by focusing on whether the valves are open or closed.
  • This sensor is used in a car engine to measure the position & revolution of the camshaft,
  • These are used within BLDC motors or used in automobiles.
  • This sensor is utilized in some Vauxhall ECOTEC engines.

Thus, this is an overview of the camshaft position sensor, its working, and its applications. This is an electronic component used to gather information on the rotating speed & camshaft positioning. It transmits the data to the electronic control unit of the vehicle so that it sets the timing for the ignition systems & fuel injection. There are many reasons for the camshaft sensor failure like short circuits internally, mechanical damage, break within the encoder wheel, and interruption within connection to the CU (control unit). Here is a question for you, what is a crankshaft position sensor?