Where is the crankshaft position sensor located on an engine?
This blog will answer the following questions: where is the crankshaft position sensor located on an engine? What are the types of crankshaft sensors used in the internal combustion engine? How to diagnose a faulty crankshaft position sensor? Can you drive a car with a faulty crankshaft position sensor?
Where is the crankshaft position sensor located on an engine?
The crankshaft position sensor is located at the back of the engine on the timing case cover. There is an especially designed hole on the timing case that allows the probe of the crankshaft position sensor to detect the teeth on the flywheel which is connected to the crankshaft. The signal from the crankshaft position sensor or CKP is used by the engine control unit to determine the engine speed.
The engine control unit is directly connected to the crankshaft position sensor, the signal from the CKP and the throttle position sensor determines the engine load. Based on the engine load, the engine control unit controls the fuel injection quantity and also the start of the injection.
There are two missing teeth or a gap in the flywheel. This gap represents the start of a new ignition cycle, in an internal combustion engine, all four strokes are completed in two rotations or 720 degrees of the crankshaft.
The camshafts rotate at twice the speed of the crankshaft, there are usually two camshaft position sensors located on the cylinder head cover to detect the speed of the camshafts.
The reference voltage required for the operation of the sensors is provided by the engine control unit. The amplitude of the signal wave increases with the increase in the engine speed. The waveform can be seen with the help of an oscilloscope and it is in the form of a square wave.
What are the types of crankshaft position sensors used in an internal combustion engine?
There are two types of crankshaft position sensors used in an internal combustion engine, they are as follows:
Hall effect sensor
This type of crankshaft position sensor is the most common and widely used sensor in the internal combustion engine. The CKP uses the Hall effect principle; there is an electromagnet in the sensor probe of the CKP. It is located at a 1-2 mm distance from the sensor rotor ring located on the flywheel.
The sensor rotor rings have gaps across the periphery and as the crankshaft is rotated, the sensor produces a voltage signal where each pulse represents a gap in the sensor rotor ring.
The waveform of the voltage signal is a digital square wave, without the power supply from the engine control unit; the hall effect type crankshaft position sensor cannot generate the signal voltage.
Metal shavings or any dirt can affect the signal voltage generated by the CKP. if the gaps or teeth on the flywheel are also damaged then the engine control unit cannot detect the correct position of the crankshaft and engine speed will not be accurate.
Magnetic pickup sensor
This type of crankshaft position sensor is used in the latest internal combustion engines. There is a magnetic multipole ring attached to the crankshaft of the engine instead of the flywheel. Therefore the design of the flywheel can be made lighter as only the starter ring gear is present in the circumference of the flywheel.
The electrical cables are also less for the magnetic pickup sensor, as the crankshaft rotates the multipole ring is also rotating at the same speed. The magnetic pickup detects the change in the magnetic field produced by the sensor rotor ring and sends the signal back to the engine control unit. There is no need for a reference voltage from the ECU for the operation.
The magnetic pickup sensor is more reliable compared to the hall effect crankshaft position sensor. It can detect the engine speed more accurately and there is no effect on the signal voltage if the sensor probe is dirty or there are metal shavings present on the tip.
The sensor will keep working as long as the sensor rotor ring is not damaged or dirty. The ring is installed outside of the crankshaft back oil seal and the probe must be at a distance of 2 to 3 mm from the multipole ring.
How to diagnose a faulty crankshaft position sensor?
The procedure to diagnose a faulty crankshaft position sensor is given below, special tools like a digital multimeter, socket box, and oscilloscope can easily diagnose a faulty crankshaft position sensor.
- Perform a visual inspection of the electrical lines and there should be no loose contact or corrosion on the electrical couplers that can cause high contact resistance.
- Connect the socket box and insert the probes of the digital multimeter into the appropriate pin number of the crankshaft position sensor.
- Start or crank the engine and observe the voltage in the multimeter, it should be between 9 to 12 volts when the engine is idling.
- Connect the oscilloscope and observe the waveform, the signal wave must be square shaped and the amplitude should be according to the manufacturer’s specification.
If the signal voltage and the electrical lines are okay then replace the crankshaft position sensor and erase the fault code. If there is no voltage from the engine control unit then the PCB in the engine control unit is responsible for the incorrect engine speed and the ECU must be replaced.
Can you drive a car with a faulty crankshaft position sensor?
Yes, it is possible to drive a car with a faulty crankshaft position but the ability of the engine to operate depends on the programming of the engine control unit. If the engine control unit detects no signal from the crankshaft sensor it will use the camshaft position sensor to determine the ignition angle of the engine.
If the signal from the crankshaft and the camshaft sensors is available then the engine cannot be started as the ignition angle is required for the start of the fuel injection and the fuel injection quantity. If it is a petrol engine then the vehicle cannot be driven with a faulty crankshaft sensor as the engine ECU does not have failsafe mode and the engine speed in petrol engines is very high compared to diesel engines.
The engine malfunction light or EOBD light is also active because fault code P0335 is present in the fault code memory of the engine control unit, if there are any other critical faults then the driver cannot be warned and there can be catastrophic damage to the internal combustion engine.
This blog answered the question where is the location of the crankshaft position sensor in an internal combustion engine and also stated the different types of crankshaft position sensors found on modern engines. Diagnosis of the crankshaft position sensor is fairly easy and concerns like the vehicle not starting or long cranking can be rectified by replacing a faulty crankshaft position sensor.