Updated: Jun 13
✔ This article has been fact checked.
The crankshaft position sensor, also known as the engine speed sensor, is an important component in your vehicle's ignition system. It's responsible for monitoring the position and rotational speed of the crankshaft, it sends this data to the engine control module (ECM).
If the sensor is not functioning properly, it can cause issues with your vehicle's ignition timing, fuel efficiency, and overall performance.
There are two ways to test a crankshaft position sensor, depending on whether you have an inductive or hall-effect sensor. You will need a digital multimeter to complete the test.
In this guide, we will show you how to test a crankshaft sensor step-by-step to determine if it is functioning correctly. Before beginning, make sure to gather the necessary tools and materials, and refer to your vehicle's service manual for specific instructions and safety guidelines.
Table of Contents:
What a Crankshaft Position Sensor Is
A crankshaft position sensor (CKP) is a device that is used to determine the position and rotational speed of the crankshaft in an internal combustion engine. These sensors are typically located on the engine block.
Crankshaft position sensors work by detecting the movement of the crankshaft as it rotates. They do this by using a variety of different techniques, such as inductive sensing, Hall effect sensing, or optical sensing.
When the crankshaft position sensor detects movement, it sends a signal to the engine control unit (ECU), which uses this information to adjust the timing of the ignition and fuel injection systems.
The main function of a crankshaft position sensor is to provide the ECU with accurate and timely information about the position of the crankshaft. This information is used to optimize the performance of the engine, and to ensure that it is running smoothly and efficiently.
In addition to its role in engine management, the crankshaft position sensor is also used in a variety of other automotive systems, such as transmission control, stability control, and traction control. So, it is a very important component of a vehicle.
Types of Crankshaft Position Sensor
There are two main types of crankshaft position sensors that are commonly used in vehicles.
Inductive (Magnetic) Crankshaft Sensor
An inductive crankshaft sensor is a type of magnetic (variable reluctance) sensor that is used to determine the position of the crankshaft. These sensors typically have one or two wires, and are mounted in front of a rotor or reluctor wheel.
When the sensor is triggered, it produces its own AC voltage signal, which can be used to determine the position of the crankshaft.
Hall-Effect Crankshaft Sensor
A Hall-effect crankshaft sensor is a type of digital sensor that uses the Hall effect to determine the position of the crankshaft. These sensors typically have three or four wires, and are also mounted in front of a rotor or reluctor wheel.
When the sensor is triggered, it generates a digital (square wave) signal, which can be used to determine the position of the crankshaft.
Unlike inductive crankshaft sensors, Hall-effect sensors require an outside power source and a ground connection in order to produce their signal.
How to Test an Inductive Type Crankshaft Position Sensor
To test an inductive type crankshaft position (CKP) sensor, follow these steps as an example. Note that some manufacturers include a protective shield on the sensor's wiring, under the insulation, to prevent electrical interference.
It is also possible that your vehicle may have a third wire on the harness connector.
Be sure to refer to your vehicle repair manual for the electrical value specifications and any recommended testing procedures specific to your vehicle model. It is important to follow the manufacturer's guidelines to ensure accurate and safe testing of the crankshaft sensor.
You will need a digital multimeter to complete the testing.
To prevent the engine from starting during the testing process, you can take the following precautions.
Disable the fuel system by removing the fuel pump fuse or relay.
Disconnect the ignition cable between the ignition coil and distributor.
It is always a good idea to consult your vehicle repair manual for specific instructions on disabling the engine for your particular vehicle model. These steps will ensure that the engine remains off while you are conducting the crankshaft position sensor test.
To test an inductive type crankshaft position sensor, follow the steps below.
Unplug the crankshaft sensor electrical connector.
Set your digital multimeter to the DC voltage scale on a low range.
Turn the ignition key to the "On" position, but do not start the engine.
Touch the black lead of the multimeter to a grounded surface, such as a clean spot on the engine, a metal bracket, or the negative (-) post of the battery.
Touch the red lead of the multimeter to each of the sensor wires on the unplugged connector. One of the wires should produce around 1.5 volts. If it does not, the sensor is not receiving a reference voltage and needs to be fixed.
Set your digital multimeter to the AC voltage scale on a low range.
Connect the meter leads to the sensor pins, making sure to keep the lead wires away from any moving engine parts.
Have an assistant crank the engine for a few seconds while you observe the meter's readout. The sensor should produce a voltage pulsing signal. If no voltage pulses are present, the sensor should be replaced. If your multimeter has a frequency (Hz) setting, you can use this in the same way to check for an AC signal. Compare your results to the manufacturer's specifications as listed in your vehicle repair manual.
How to Test the Crankshaft Position Sensor Resistance
To check the resistance of your inductive crankshaft position sensor, follow the steps below.
Set your digital multimeter to the Ohms scale.
Unplug the crankshaft position sensors electrical connector.
Connect one lead of the multimeter to one of the sensor pins and the other lead to the other sensor pin. It does not matter which order you connect the leads.
Turn on the multimeter.
The readout should display a resistance value, typically between 200 and 2000 ohms, depending on your specific vehicle model.
Compare this value to the manufacturer's specifications, which can be found in your vehicle repair manual.
If the value is outside of the specified range, you should replace the crankshaft position sensor.
If the readout displays infinite resistance, the sensor has an open circuit. If the readout displays zero ohms, the sensor has a short circuit.
It is not recommended to test the resistance of a Hall effect type crankshaft position sensor. This is because the induced voltage during testing can potentially interfere with the normal operation of a functioning sensor.
How to Test a Hall Effect Type Crankshaft Position Sensor
To test a Hall effect type crankshaft position sensor, it is best to use an oscilloscope, although many DIY enthusiasts do not own one. However, it is possible to test this type of sensor using a digital multimeter (DMM).
It is important to note that, unless specified in your vehicle repair manual, you should not check the resistance of a Hall effect CKP sensor. The induced voltage during testing can potentially damage internal components.
While a DMM will not provide the high and low voltage graphic or frequency readings that an oscilloscope would, it can still give you an idea of the sensor's operation by displaying the average voltage coming from the sensor.
Keep in mind that this method may not be as accurate as using an oscilloscope, but it can still be a useful tool in diagnosing potential issues with the sensor.
To prevent the engine from starting during testing, you can take the following precautions.
Remove the fuel pump fuse or relay.
If your engine has a distributor, you can unplug the center ignition cable and ground it to the engine using a jumper wire.
Be sure to consult your vehicle repair manual for specific instructions on disabling the engine in your particular model. These steps will ensure that the engine remains off while you are conducting the test.
To test a Hall effect crankshaft position sensor using a digital multimeter, follow the steps below.
Unplug the sensor's electrical connector.
Set your DMM to the DC volts range and a range of 20 volts.
Touch the black lead of the DMM to the black wire on the harness connector.
Touch the red lead of the DMM to the red (power) wire on the harness connector. Note that the colors of the wires may vary depending on your vehicle model, so be sure to consult the wiring diagram for your specific model.
Turn the ignition key to the "On" position. The DMM should read between 5 and 13 volts. Refer to your vehicle repair manual for the reference voltage value for your model. If the reference voltage is lower than expected or zero, check the wire and connector for damage or loose terminals. If necessary, check your car's computer.
Turn the ignition off and reattach the crankshaft position sensor to the harness connector.
Set the DMM to a low DC voltage range that is capable of reading millivolts.
Touch the black lead of the DMM to the negative terminal of the battery.
Using the red lead, back probe the black, ground wire at the harness connector or CKP sensor.
Have an assistant crank the engine for a few seconds. The DMM should register around 200 to 300 mv.
Touch the red lead of the DMM to the green (signal) wire on the harness connector or CKP sensor.
Crank the engine for a few seconds. The DMM should register around 300 mv. This is an average voltage value of the signal produced by the crank sensor.
If necessary, compare your results to the specifications in your vehicle repair manual. If your DMM is capable of reading Duty Cycle signals, you may be able to detect a crankshaft signal as well, depending on your vehicle's system.
To do this, back probe the signal wire on the sensor and connect the black lead of the DMM to ground.
Set the DMM to the Duty Cycle function.
Have an assistant crank the engine.
If the CKP sensor does not produce a duty cycle signal, it may be faulty.
Remember to refer to your vehicle repair manual for specific instructions and guidelines for testing the crankshaft position sensor in your particular model.
Wikipedia. "Crankshaft position sensor" https://en.wikipedia.org/wiki/Crankshaft_position_sensor
Wikipedia. "Inductive sensor" https://en.wikipedia.org/wiki/Inductive_sensor
Wikipedia. "Hall effect sensor" https://en.wikipedia.org/wiki/Hall_effect_sensor
Dan Ferrell. (May 30, 2022) https://axleaddict.com/auto-repair/How-to-Test-a-Crankshaft-Position-Sensor-Using-a-Multimeter