What Is A Crankshaft Position Sensor?

Your car has a variety of sensors on board that regulate other parts of your car and keeps your performance in check. Without properly working sensors in places like your engine, your car can become increasingly unreliable in more ways than one, and you run the chance of being stranded with a broken-down car. Many of these sensors are extremely important, and the crankshaft position sensor is one of those.

Today, we are discuss why the crankshaft sensor is so important to your vehicle, what the symptoms of a bad crankshaft sensor look like, and what to do if you suspect it to be to blame for your recent engine problems.

What is a Crankshaft Position Sensor?

A crankshaft position sensor is an electronic device used in an internal combustion engine, both petrol and diesel, to monitor the position or rotational speed of the crankshaft.

This information is used by engine management systems to control the fuel injection or the ignition system timing and other engine parameters. Before electronic crank sensors were available, the distributor would have to be manually adjusted to a timing mark on petrol engines.

The crank sensor can be used in combination with a similar camshaft position sensor to monitor the relationship between the pistons and valves in the engine, which is particularly important in engines with variable valve timing.

This method is also used to “synchronise” a four stroke engine upon starting, allowing the management system to know when to inject the fuel. It is also commonly used as the primary source for the measurement of engine speed in revolutions per minute.

Common mounting locations include the main crank pulley, the flywheel, the camshaft or on the crankshaft itself. This sensor is one of the two most important sensors in modern-day engines, together with the camshaft position sensor.

As the fuel injection (diesel engines) or spark ignition (petrol engines) is usually timed from the crank sensor position signal, failing sensor will cause an engine not to start or will cut out while running. Engine speed indicator takes speed indication also from this sensor.

Crankshaft Position Sensor

What Does A Crankshaft Position Sensor Do?

The functional objective for the crankshaft position sensor is to determine the position and/or rotational speed (RPM) of the crank. Engine Control Units use the information transmitted by the sensor to control parameters such as ignition timing and fuel injection timing.

In a diesel, the sensor will control the fuel injection. The sensor output may also be related to other sensor data including the cam position to derive the current combustion cycle, this is very important for the starting of a four-stroke engine.

Sometimes, the sensor may become burnt or worn out – or just die of old age at high mileage. One likely cause of crankshaft position sensor failure is exposure to extreme heat. Others are vibration causing a wire to fracture or corrosion on the pins of harness connectors.

Many modern crankshaft sensors are sealed units and therefore will not be damaged by water or other fluids. When it goes wrong, it stops transmitting the signal which contains the vital data for the ignition and other parts in the system.

A bad crank position sensor can worsen the way the engine idles, or the acceleration behaviour. If the engine is revved up with a bad or faulty sensor, it may cause misfiring, motor vibration or backfires. Acceleration might be hesitant, and abnormal shaking during engine idle might occur. In the worst case, the car may not start.

The first sign of crankshaft sensor failure, usually, is the refusal of the engine to start when hot but will start again once the engine has cooled.

One detail of some designs is the “three-wire” inductive crank sensor whereby the third wire is actually just a co-axial shield around the two main sensor wires to prevent them from picking up stray electrical pulses from elsewhere in the vehicle engine bay.

Functions of Crankshaft Position Sensor

  • The crankshaft position sensor can detect the engine speed, determine the fuel injection amount and ignition advance Angle, and avoid the phenomenon of reduced fuel injection amount.
  • The crankshaft position sensor can detect the reference position of the engine reference cylinder and distinguish the cylinder sequence.
  • The crankshaft position sensor can detect the Angle of the crankshaft rotation, determine any position of the piston operation, determine the ignition time and fuel injection time, and help the best moment of the car ignition.
  • In addition to controlling fuel injection and ignition, crankshaft position sensor is also used for idle speed control, fuel evaporation control, etc., reasonable use of crankshaft position sensor can have a more accurate understanding of the working situation of the car.
  • Collect the crankshaft rotation Angle and engine speed signal, and input the ECU, in order to determine the injection sequence, injection timing, ignition sequence, ignition timing, and then according to the signal monitoring of the crankshaft Angle fluctuation size to determine whether the engine fire phenomenon.

Issues And Causes of The Bad Crankshaft Position Sensor

  • Overheating Engine: The engine temperature is higher than normal temperature causing melting of the plastic covering and leading to crankshaft sensor damage
  • Circuitry Problems: The CKP sensor can’t send the signal to Powertrain Control Module (PCM) because of faulty voltage or loose, worn-out, or damaged wiring
  • Broken timing belt.

Symptoms Of a Bad Crankshaft Position Sensor

The CKP sensor is a primary input to the PCM, a faulty sensor can cause a range of different problems. These are the most common bad crankshaft position sensor symptoms:

1. Check Engine Light Illumination

If have problems with the crankshaft position sensor, the check engine will illuminate to inform the driver.

2. Hard Starting And/Or Stalling

The CKP is responsible for monitoring the position, speed of the crankshaft, and other parameters that play an important role when starting the engine. When the CKP has an internal fault, it can not send the signal to PCM. This cause the engine to start hard or stall

3. Engine Runs Rough Or Misfires

The most common symptom associated with a bad/faulty crankshaft position sensor is the engine runs rough or misfires. The failing CPK can not provide the right information about the position of a piston in the engine, causing a misfire. This fault may pose damage to components and should be repaired as soon as possible.

4. Poor Fuel Economy

The faulty CPK sensor that lacks accurate timing information may cause fuel injectors won’t pump fuel into the engine efficiently, the vehicle will be lost power and consume more fuel. If you notice that the car consumes more fuel when you drive at the same distance, it’s a sign of a bad CKP sensor.

Consequences Of Ignoring A Bad Crankshaft Position Sensor

Ignoring a bad crankshaft position sensor can lead to a variety of serious consequences for your vehicle. Here are some potential outcomes if the problem is not addressed:

  • Engine damage. The sensor’s role in managing ignition timing and fuel injection is crucial, and when these processes are disrupted, it can lead to inefficient combustion and stress on various engine parts.
  • Poor performance. A car with a bad sensor might experience rough idling, prolonged cranking, or may not start at all. These issues obviously can make driving difficult and potentially unsafe.
  • Decreased fuel efficiency. A bad sensor can disrupt the timing of your fuel injection, leading to decreased fuel efficiency and cause you to spend more on gas than you should be.
  • Sudden stalling. A bad sensor can cause your engine to stall suddenly, which can be dangerous, especially if you’re driving at high speeds or in heavy traffic.
  • Wear and tear. Ignoring the symptoms of a bad crankshaft position sensor can result in rapid wear and tear of various engine parts, leading to costly repairs down the road.

How to Test a Crankshaft Position Sensor

When your check engine light is on, you should first use a diagnostic scan tool to read the engine code before diving in and replacing the crank position sensor (CKP sensor). Issues with the crankshaft position sensor generally display codes between P0335 and P0338.

If the trouble code is related to the CKP sensor, visually inspect the sensor for cracks, loose or corroded connector pins, and other signs of damage.

If everything looks good, try one of these tests.

#1. Check the cable connecting the sensor

The crankshaft position sensor failure may be caused by a fault in the sensor connection line. Therefore, it is first necessary to check whether the sensor connection line is normal, such as whether the line is open, short circuit and other problems. If there is a problem with the line, it needs to be repaired in time.

#2. Replace the sensor

If the inspection finds that the sensor connection is normal, then the crankshaft position sensor may need to be replaced. Replace the sensor correctly according to the model and maintenance manual. When replacing a sensor, pay attention to the sensor specifications and models to ensure that the new sensor matches the vehicle.

#3. Check the engine control system

Crankshaft position sensor failure can also be caused by a problem with the engine control system. Therefore, after checking the sensor itself and the connection line, it is also necessary to check whether there is a problem with the engine control system. If there is a problem with the engine control system, it needs to be repaired or replaced in a timely manner.

#4. Check vehicle maintenance history

Sometimes the crankshaft position sensor failure can be caused by incomplete or faulty vehicle maintenance history.

For example, some service operations may cause damage to the sensor or change the sensor’s parameter Settings. Therefore, when troubleshooting, it is necessary to carefully check the vehicle maintenance history to understand the previous maintenance and operation.

Sensor Replacement Process

  • Find the crankshaft position sensor: First you need to find the position of the crankshaft position sensor. It is usually mounted on the front or side of the engine assembly and is relatively easy to spot. If you are unsure, check the vehicle’s owner’s manual or consult a professional technician.
  • Power off: Before replacing the sensor, first disconnect the power supply to avoid any accidents. Locate your car’s battery and remove the negative using a wrench. Keep in mind that when the power is disconnected, some vehicle Settings, such as car stereo and radio Settings, may be lost.
  • Remove the original crankshaft position sensor: Once you have found the sensor, you need to remove it. It is usually necessary to use a screwdriver or wrench to tighten or loosen the sensor clockwise or counterclockwise.
  • Install new crankshaft position sensor: Once the original sensor is removed, the new sensor can be installed to the same position. Make sure the new sensor is properly installed and then tightened with a screwdriver or wrench.
  • Post-test: Reattach the battery and start the car and let the car run for a few minutes to make sure the sensor works the way you set it up. If all is well, resume operations and be ready to drive!

How much does it cost to replace a crankshaft sensor?

The average cost for a Crankshaft Position Sensor Replacement is between $178 and $238. Labor costs are estimated between $96 and $121 while parts are priced between $82 and $117.

This range does not include taxes and fees, and does not factor in your unique location. Related repairs may also be needed.

Please note that these are rough estimates and the actual cost can vary. It’s always a good idea to get a quote from a trusted mechanic or auto repair shop for the most accurate estimate.