Your car has many different sensors on board, one of which is the crankshaft position sensor (CKP). Like any other car part, the crankshaft position sensor can eventually fail, and when it does, it can cause a variety of problems.
A faulty CKP sensor can turn on your car’s check engine light, leave you stranded—and more. It’s a problem you’ll want to address right away.
What is a Crankshaft Position Sensor?
A Crankshaft Position Sensor (CKP) is an electronic component used in an internal combustion engine to monitor the position and rotational speed (RPM) of the crankshaft. The electronic control unit (ECU) uses this information to control fuel injection, the ignition system timing, and other engine parameters.
The sensor is installed near the main pulley, the flywheel, the camshaft, the transmission bell housing, the engine block, or the crankshaft itself.
What Does a Crankshaft Position Sensor Do?
The functional objective of the crankshaft position sensor is to determine the position and 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 vibrations 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 behavior. 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.
Symptoms of a bad crankshaft position sensor
Recognizing the signs of a faulty crankshaft position sensor can prevent further damage and costly repairs. Here are some common symptoms:
- Trouble starting the engine
- Intermittent stalling.
- Check Engine Light is on.
- Poor acceleration.
- Fuel efficiency concerns.
#1. Engine Refuses to Start.
A gas-powered engine needs three primary ingredients to run: spark, an air-fuel mixture, and compression.
When the CKP sensor fails, the PCM doesn’t know when to fire the spark plugs and pulse the fuel injectors. As a result, the engine may be starved of fuel and/or spark, resulting in a vehicle that refuses to start.
#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 cannot send the signal to PCM. This causes the engine to start hard or stall.
#3. The 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 cannot 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. Check Engine Light illumination.
The PCM monitors the CKP sensor and its circuit. If the module detects a problem, it will turn on the check engine light and store a corresponding diagnostic trouble code (DTC) in its memory.
#5. 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.
How to Tell if Your Crankshaft is Faulty
If your engine refuses to start and your ignition continues to click over without any success, you may be able to blame it on a faulty crankshaft position sensor.
Without it, your engine will have trouble knowing when to fire the spark plugs or even inject fuel, so good luck getting things started!
How to Test a Crankshaft Position Sensor
If you’re able to locate your crankshaft position sensor under your hood, commonly found either in the front or the back of the crankshaft on a bell housing or tucked behind something, you can complete the following test to determine if your engine not starting can be blamed on your sensor:
- Inspect the sensor: Look for signs of damage to the housing, as it can commonly get burnt or covered in dirt, oil, or other debris and stop working correctly.
- Use a multimeter: If you have a multimeter on hand, pull it out, put it on the ohms setting, and take the sensor’s measurement.
- Read the results: The meter should read a resistance value anywhere from 200 to 1,000 ohms (or more depending on the model). If it has 0 ohms, it will need to be replaced.
What Causes Damage to Your Crankshaft Sensor?
The general use of your car will generally cause wear and tear to your sensor, because it’s used every time you drive and because most car parts will not last forever.
However, in case there’s something going on besides normal wear and tear, it’s important to know what may have, or is, causing damage to your crankshaft sensor.
The two most common causes of damage to the crankshaft position sensor include:
Extreme Heat
Although it isn’t the most ideal situation, the housing on the outside of your vehicle’s crankshaft sensor is plastic.
If you’ve been pushing the limits of your engine, your engine has recently overheated, or you just live in hot weather, this plastic can melt away, causing the sensor to become exposed and become dirty or damaged by heat or water.
Electrical Problems
Loose, worn-out, or damaged wiring can disrupt signals sent to and from the crankshaft sensor, causing it to malfunction.
The good news is that this rarely has anything to do with the sensor itself. The bad news: you’ll have to seek out help determining the cause of the circuitry problems.
Troubleshooting Tips and Solutions
If you’re thinking the crankshaft position sensor might be bad, be sure before you replace it. Otherwise, your symptoms might still be present, and you’ll be out the time and money for your new sensor.
- Are all of the DTCs plausibly related to the crankshaft position sensor? Some codes might be present that can indicate some other issue that might be a more likely culprit for your symptoms.
- Is the sensor clean? Remove the sensor if it doesn’t require major disassembly. Check for dirt or oil on the sensor, clean it and re-install it, and check if the problem has cleared up.
- Is the connector tight and clean inside? A corroded or loose connector could be to blame, ending up as a quick fix.
If all of your efforts still lead you to a bad crank sensor, install a new one, clear the codes, and check if the symptoms are resolved.