The crankshaft and camshaft position sensors, which are the most significant in any engine, are critical to the distributor’s and ignition timing’s performance. The crankshaft position sensor (CKP) is a multipurpose sensor that controls ignition timing, detects RPM and calculates relative engine speed.
Manual distributor timing is no longer necessary thanks to this sensor. To synchronize the fuel injector and coil firing sequence, the camshaft position sensor is employed to detect which cylinder is firing.
Now, let’s get into more details about the crankshaft position sensor!
What is a Crankshaft Position Sensor?
Crank sensors are electronic devices that monitor the position or rotational speed of the crankshaft in internal combustion engines, both gasoline and diesel. Engine management systems employ this data to adjust the timing of fuel injection and other engine characteristics.
The distributor had to be manually set to a timing mark on gasoline engines until electronic crank sensors were available. The crank sensor can be used in conjunction with a camshaft position sensor to monitor the engine’s piston-valve relationship, which is especially significant in engines with variable valve timing.
This procedure is also used to “synchronize” a four-stroke engine when it first starts, allowing the management system to determine when to inject gasoline.
It is also widely used to determine engine speed in revolutions per minute. The main crank pulley, the flywheel, the camshaft, and the crankshaft itself are all common attachment points.
This sensor, together with the camshaft position sensor, is one of the two most critical sensors in modern engines.
Because the crank sensor position signal is used to time the fuel injection (diesel engines) or spark ignition (petrol engines), a failed sensor will cause the engine to not start or cut out while running. This sensor also provides speed information to the engine speed indicator.
Functions
The following are the functions of crankshaft position sensors:
- The crankshaft position sensor’s primary function is to determine the crank’s position and/or rotational speed (RPM).
- The information sent by the sensor is used by engine adjustment units to control factors such as ignition timing and fuel injection timing.
- In diesel engines, the sensor will control the fuel injection.
- The sensor output may also be linked to other sensor data, such as the cam position, to determine the current combustion cycle, which is critical for a four-stroke engine’s beginning.
The primary functions of a crankshaft position sensor include:
Sensing
A powerful magnet can be found next to the crankshaft if you look closely. Around the crankshaft, you’ll also notice steel pins or pegs positioned at regular intervals. This magnet emits a continuous magnetic field all of the time.
The steel pins around the crankshaft rotate around this field as the engine starts and the crankshaft spins.
As a result of the variation in the field, an AC (alternating current) signal is produced. This also instructs the engine management unit (engine computer) to determine the rotational speed.
As a result, the EMU can compute the camshaft’s position and speed to improve fuel injection and ignition.
Adjustments
We must learn one thing from modern automobiles. Only if the internal parts are moving at the specific required pace will the engines provide us with efficient performance. The onboard computer can only use the information sent to it by the crankshaft position sensor once it detects the rotation of the crankshaft inside the engine.
This is when the computer makes little adjustments or fine-tunes the engine to improve its efficiency. Consider the situations in which you’re going full throttle. The computer needs to make these tiny adjustments to the engine to modify the speed in settings like cruise mode or sports mode because the throttle is constant.
The computer will make sure that the crankshaft’s rotational speed is constantly monitored, and compared to the appropriate range, and speed adjustments are made as needed. This adjustment can be made in terms of both speed increases and speed decreases.
Types of a Crankshaft Position Sensor
The following are the various types of crankshaft position sensors:
Inductive:
in this type of crankshaft position sensor, a magnet is used to detect a signal from the engine cranking. Either in the engine block, close to the flywheel, or close to the crankshaft itself.
Notches on a spinning disk, relay wheel, or crankshaft are picked up by it. The magnetic field changes as each notch passes, sending an alternating current signal to the ECU.
Hall Effects:
This type is similar to the inductive sensor in that it is positioned in the same locations and responds to the same notches. It creates a digital signal instead of an analog AC signal. As the notches travel by the sensor, it turns on or off.
AC Output Sensor:
The output of an AC output sensor differs from that of other sensors in that it is an AC voltage signal. The exciter coil, which is placed near the rotating disc, receives a very high frequency (between 150 and 2500 cycles per second) from the onboard controller.
This disc has a slot in it and is attached at the end of the camshaft. The mutual inductance excites the slot as it goes through the coil, and a signal specifying the position of the first cylinder is sent to the onboard controller. Some Vauxhall ECOTEC engines employ this type of sensor.
Working Principle
The workings of a crankshaft position sensor are less complex and can be easily understood. In its working state, the teeth on the reflector ring attached to the crankshaft pass near the sensor tip on the crankshaft position sensor.
One or more teeth are missing from the reluctor ring, which serves as a reference point for the engine computer (PCM).
The sensor generates a pulsed voltage signal when the crankshaft spins, with each pulse corresponding to a tooth on the reluctor ring.
With the engine idling, the photo below displays the actual signal from the crankshaft position sensor. As you can see from the graph, the reluctor ring in this vehicle has two missing teeth.
The PCM uses the signal from the crankshaft position sensor to determine when and in which cylinder to fire the spark.
The signal from the crankshaft position is also utilized to check for misfires in the cylinders. There will be no spark and the fuel injectors will not operate if the sensor signal is missing.
Magnetic sensors with a pick-up coil that produces A/C voltage and Hall-effect sensors that produce a digital square wave signal, as shown in the photo above, are the two most prevalent varieties.
Hall-effect sensors are used in modern automobiles. A two-pin connector is found on a pick-up coil sensor. A three-pin connector is used to connect the Hall-effect sensor (reference voltage, ground, and signal).
Symptoms of a Bad Crankshaft Position Sensor
As the crankshaft position sensor goes bad, it gives one of the below-given signs:
#1. Illuminated Check Engine Light.
The illuminated check engine light is the first sign of a faulty crankshaft position sensor.
The powertrain control module (PCM) continuously communicates with the crankshaft position sensor to control different features of the engine. When the sensor goes bad, it sends inaccurate data about the crankshaft’s speed and position to the PCM.
When the PCM receives wrong information from the CKP sensor, it triggers the check engine warning light on the dashboard to alert the driver. Your PCM may also trigger the trouble codes P0335 or P0336 along with the check engine light.
#2. Excessive Engine Vibrations.
An engine with a malfunctioning crankshaft position sensor doesn’t operate at peak performance. The powertrain control module (PCM) of the vehicle uses the data of the crank sensor to regulate the ignition timing and many other features.
If your PCM uses incorrect readings from the crankshaft sensor to determine fuel and ignition timing, it may lead to a bumpy driving experience.
If the PCM fails to time these processes correctly for a long time, the issue will only worsen until it is resolved, potentially causing further damage.
#3. Hard Starting.
When a faulty crankshaft position sensor is severely out of sync, you may struggle to start your car or keep it running. This issue typically arises when the problem has persisted for a long time, potentially indicating other underlying issues.
However, if your check engine light is on and the PCM has defaulted to predetermined values, this might not be an immediate concern.
Instead, this issue usually arises when the crankshaft position sensor provides inaccurate readings, and the PCM fails to detect it.
#4. Poor Engine Performance.
As we discussed above, engine performance highly depends on the performance of the crankshaft sensor. Poor engine performance is one of the clear symptoms of a faulty crankshaft position sensor.
When this sensor goes bad, it significantly impacts the PCM’s ability to maintain proper fuel injection rate and ignition timing. As a result, you may experience a hesitation when pressing the gas pedal harder, or the engine might not respond at all. This may be particularly hazardous on roads where quick acceleration is necessary.
#5. Engine Misfire.
A faulty crankshaft position sensor may also cause misfiring. This issue occurs when a faulty crank sensor sends wrong information about the piston position to the PCM, which in turn results leads to misfires within one or more of the combustion chambers.
However, your car may misfire due to many other issues. However, a bad spark plug can also cause this issue. Therefore, it is important not to dismiss the possibility of a faulty crankshaft position sensor if you’re experiencing other related symptoms.
#6. Poor Fuel Economy.
As we discussed above, the main function of the crankshaft position sensor is to measure the crankshaft position and send this data to the PCM. The PCM utilizes this data to adjust fuel injection rate, and ignition timing, ensuring optimal engine performance and efficiency.
When the crankshaft sensor becomes faulty, it starts sending wrong information to PCM. When the PCM receives wrong information, it may be unable to efficiently regulate the fuel injection rate, resulting in a lean or rich air-fuel mixture.
The poor air-fuel mixture leads to poor combustion and your engine works hard to properly combust the mixture. As a result, your engine starts to consume more fuel than normal.
#7. Engine Stalling.
Frequent engine stalling can occur when driving with a bad crankshaft position sensor. If this issue is left unaddressed, your engine may eventually stop functioning altogether.
Your vehicle engine may stall due to many other reasons, such as a faulty fuel injector or faulty camshaft sensor. Therefore, when your engine stalls, properly inspect all the parts to find the root cause of the engine.
#8. Car Jerking.
A faulty crankshaft position sensor may lead to the car jerking while driving. When the sensor goes bad, the PCM will be unable to properly control the ignition timing and fuel injection. This leads to hesitation or sudden variations in engine speed, which may cause the vehicle to jerk.
#9. Rough Idle.
A faulty crankshaft sensor may lead to a rough idle. The crankshaft position sensor is one of the major components of the engine management system. When it becomes faulty, it may lead to poor combustion of the air-fuel mixture in the combustion chamber, which causes a rough idle.
Causes of a Bad Crankshaft Position Sensor
- Age and wear: With time, the crankshaft position sensor may degrade or wear out because of constant exposure to extreme pressure, vibration, heat, and other harsh operating environments. These harsh operating conditions may lead to the failure of the sensor.
- Physical Damage: Accidental damage to the sensor or its casing during car repairs or maintenance may also lead to its failure.
- Moisture or Corrosion: The internal parts of the sensor may damage due to corrosion or moisture.
- Damage from heat: Extreme heat for a long time may damage the internal parts of the camshaft position sensor. A high temperature may force the internal parts to expand, while a low temperature may cause brittleness or cracking.
- Contaminants: The contaminants such as debris or oil may gather inside the sensor, which affects its capability to accurately measure the crankshaft position. This may lead to erratic readings and poor performance.
- Manufacturing Material: The manufacturing material of the sensor plays a vital role in its efficient performance. A sensor made of poor material can’t work efficiently for a long time.
How To Test a Crankshaft Position Sensor
The sensor should be visually inspected for cracks, loose or corroded connector pins, or other obvious damage whenever there is a suspicion that the issue could be brought on by a crankshaft position sensor or if there is an associated fault code.
Another important component is the exact distance between the sensor’s tip and the reluctor ring.
The service handbook contains the proper testing process. At the bottom of this article, we provide a list of websites that charge a fee for access to various car service manuals: What to examine first and repair options if your engine light is on.
For instance, according to Auto Zone, the crankshaft position sensor (CKP) resistance for the 2008 Ford Escape should range from 250 to 1,000 ohms. We obtained a measurement of 285.6 ohms, which is OK (see photo). The sensor needs to be replaced if the resistance is lower or higher than what is needed.
Tests must be done on the ground signal and reference voltage (usually +5V) for Hall-type sensors. The simplest way to test a crankshaft position sensor is to use an oscilloscope to analyze the sensor signal.
The sensor can have an irregular problem that does not manifest itself during testing. In this situation, looking for Technical Service Bulletins (TSBs) and learning about typical issues may be helpful.
Using a scan tool, the crankshaft position sensor can be inspected. The sensor signal is shown as either “Engine RPM” or “Engine speed.” When might this be good?
Monitoring the sensor signal can reveal the cause of intermittent stalling: if the sensor signal abruptly goes to zero and then rises, either there is an issue with the sensor itself or with the sensor wiring or connector.
Crankshaft Position Sensor Location
The location of the crankshaft position sensor depends on the vehicle model and the type of engine. The crankshaft position sensor is usually located near the bottom of the engine, close to the crankshaft itself. This placement is logical, as the sensor’s primary function is to measure the crankshaft’s position.
To locate the crankshaft sensor, direct your attention toward the bottom of the engine, typically on one of its sides. Due to its deep-seated position within the engine, the sensor is challenging to find, and replacing or removing a bad one can be even more difficult.
How to replace a Crankshaft Position Sensor
To replace a faulty crankshaft position sensor on your own, gather some essential tools such as a new crankshaft sensor, jack stands, cleaning solution, a ratchet and socket set, and a floor jack.
- Park your vehicle in a safe place.
- Lift the vehicle with the help of a jack and put jack stands underneath it.
- Disconnect the negative terminal of the vehicle’s battery to prevent any electrical issues while working on the vehicle.
- Locate the crankshaft sensor, which can be found near the timing cover or harmonic balancer of your engine. You can also consult your vehicle manufacturer’s manual to easily locate the crank sensor.
- Disconnect all the connectors and wires connected to the sensor. After removing the mounting bolts, gently remove the sensor from its mount.
- Clean the area surrounding the sensor mount to ensure a proper seal when installing the new sensor.
- Properly lubricate the O-ring on the replacement sensor for easy installation.
- Place the new sensor into the mount and secure it with the mounting bolts.
- Reinstall all other parts back in their original places.
- Reconnect the negative terminal of the battery.
- Turn on the engine to test the newly installed sensor. If your engine starts immediately, it means you have successfully installed the crankshaft sensor.
- If the car fails to start, there may be another problem that requires attention.
Crankshaft Position Sensor Replacement Cost
A crankshaft position sensor can be changed for not very much money. Between $35 and $115 for the part, plus $55 to $130 for labor. Using an OEM component is recommended.
The majority of cars make it pretty simple to replace, yet sometimes rust may make it challenging to remove the sensor.
For further information, view these YouTube videos. It’s crucial to check the correct distance between the crankshaft position sensor and the teeth of the reluctor ring before installing a replacement.
That is all for this article, where I explain the crankshaft position sensor in a car. If you found it helpful, kindly share it with others. Thanks for reading; see you in the next one!