The crankshaft position sensor, also referred to as the engine speed sensor, plays a vital role in the ignition system of your vehicle.
Its job is to keep track of the crankshaft’s position and rotation speed, transmitting this information to the engine control module (ECM).
If this sensor is not operating as it should, it may lead to problems with your car’s ignition timing, fuel economy, and general performance.
Before you get started, assemble all required tools and materials. Don’t forget to consult your vehicle’s service manual for specific steps and safety measures.
In this guide, we’ll walk you through a step-by-step process on how to test a crankshaft sensor to verify if it’s working properly.
What a Crankshaft Position Sensor Is
A crankshaft position sensor (CKP) is a critical sensor that identifies the position and rotational speed of the crankshaft in an internal combustion engine.
These sensors are generally found on the engine block (see more information on the crankshaft sensor location).
They operate by monitoring the crankshaft’s rotation through various methods, including inductive sensing, Hall effect sensing, or optical sensing.
When the sensor picks up the crankshaft’s movement, it transmits a signal to the engine control unit (ECU).
The ECU then utilizes this data to manage the ignition’s timing and the fuel injection process.
The crankshaft position sensor’s primary purpose is to supply the ECU with precise, up-to-date details about the crankshaft’s position.
This data aids in maximizing the engine’s performance and guaranteeing its smooth, efficient operation.
Besides its crucial role in managing the engine, the crankshaft position sensor is also employed in numerous other car systems such as transmission control, stability control, and traction control.
Thus, it’s an essential part of a vehicle.
Crankshaft Position Sensor Types
There are primarily two categories of crankshaft position sensors frequently found in vehicles.
- Inductive (magnetic)
Inductive (Magnetic) Crankshaft Sensor
An inductive crankshaft sensor is a kind of magnetic sensor (also known as variable reluctance sensor) used to figure out the crankshaft’s position.
These sensors generally come with one or two wires and are placed before a rotor or a reluctor wheel.
Upon activation, the sensor generates its own AC voltage signal, which can be used to pinpoint the crankshaft’s position.
Hall-Effect Crankshaft Sensor
A Hall-effect crankshaft sensor is a digital sensor variety that employs the Hall effect to ascertain the crankshaft’s position.
These sensors usually come with three or four wires and are likewise situated ahead of a rotor or reluctor wheel.
Upon activation, the sensor produces a digital (square wave) signal, utilized to identify the crankshaft’s position.
Contrary to inductive crankshaft sensors, Hall-effect sensors necessitate an external power supply and a grounding connection to generate their signal.
How to Test an Inductive Type Crankshaft Position Sensor
To examine an inductive type crankshaft position (CKP) sensor, you can follow the steps mentioned below as a reference.
Keep in mind that some manufacturers may embed a protective shield under the insulation of the sensor’s wiring to avoid any electrical disturbance.
Your vehicle may also feature a third wire on the harness connector.
Always refer to your vehicle repair manual for the specific electrical value specifications and any suggested testing procedures applicable to your car model.
It’s crucial to adhere to the manufacturer’s instructions to guarantee safe and precise testing of the crankshaft sensor.
You will also need a digital multimeter to complete the testing process.
To keep the engine from turning on during the test, consider the following preventative steps:
- Deactivate the fuel system by extracting the fuel pump fuse or relay.
- Unhook the ignition cable that links the ignition coil and distributor.
Always consult your vehicle’s repair manual for specific instructions on how to disable the engine for your particular model.
These measures will ensure the engine stays off while you’re performing the crankshaft position sensor test.
Here’s a step-by-step guide to testing an inductive type crankshaft position sensor:
- Detach the crankshaft sensor’s electrical connector.
- Switch your digital multimeter to the low range of the DC voltage scale.
- Turn the ignition key to the “On” position, but avoid starting the engine.
- Place the black lead of the multimeter on a grounded surface, such as a clean area on the engine, a metal bracket, or the battery’s negative (-) post.
- Apply the red lead of the multimeter to each of the sensor wires on the detached connector. One of the wires should yield approximately 1.5 volts. If it doesn’t, the sensor is not receiving a reference voltage and needs to be repaired.
- Set your digital multimeter to the low range of the AC voltage scale.
- Attach the meter leads to the sensor pins, taking care to keep the lead wires away from any moving engine parts.
- Ask someone to crank the engine for a few seconds while you watch the meter’s display. The sensor should produce a voltage pulsing signal. If no voltage pulses are evident, the sensor should be replaced. If your multimeter has a frequency (Hz) setting, you can use it in the same manner to check for an AC signal. Contrast your results with the manufacturer’s specifications as stated in your vehicle repair manual.
How to Test the Crankshaft Position Sensor Resistance
Here’s a straightforward guide to check the resistance of your inductive crankshaft position sensor.
- Adjust your digital multimeter to the Ohms scale.
- Detach the electrical connector of the crankshaft position sensor.
- Attach one lead of the multimeter to one of the sensor pins and the other lead to the remaining sensor pin. The sequence of connection isn’t crucial.
- Switch on the multimeter.
You should see a resistance value on the readout, generally in the range of 200 to 2000 ohms, although this might vary depending on your specific vehicle model.
Match this value with the manufacturer’s specifications, which you can find in your vehicle’s repair manual.
- If the value is not within the specified limits, you ought to replace the crankshaft position sensor.
- If the readout shows infinite resistance, the sensor has an open circuit.
- If it reads zero ohms, the sensor has a short circuit.
It’s worth noting that it’s generally advised against testing the resistance of a Hall effect type crankshaft position sensor.
This is because the voltage generated during testing can possibly disturb the normal function of a working sensor.
How to Test a Hall Effect Type Crankshaft Position Sensor
To test a Hall effect type sensor, it’s best to use an oscilloscope, although most people do not own this specific tool.
It is possible to test a Hall effect type of sensor without this tool by using a digital multimeter (DMM).
It’s crucial to remember that unless your vehicle repair manual suggests otherwise, it’s not advisable to check the resistance of a Hall effect Crankshaft Position (CKP) sensor.
Doing so may result in damage to internal components due to the voltage induced during testing.
Although a Digital Multimeter (DMM) does not provide the detailed high and low voltage graphics or frequency readings an oscilloscope can, it can still offer a rough idea of the sensor’s function by showing the average voltage from the sensor.
Bear in mind this method might not be as precise as using an oscilloscope, but it can still serve as a handy tool in pinpointing potential issues with the sensor.
To keep your engine from starting while you test, consider the following steps.
- Pull out the fuel pump fuse or relay.
- If your engine is equipped with a distributor, detach the central ignition cable and ground it to the engine using a jumper wire.
Always consult your vehicle repair manual for specific instructions on disabling the engine for your particular model. This will ensure your engine stays off during the test.
To use a digital multimeter in testing a Hall effect crankshaft position sensor, follow these steps below.
- Disconnect the sensor’s electrical connector.
- Set your DMM to the DC volts range and a scope of 20 volts.
- Connect the black lead of the DMM to the black wire on the harness connector.
- Connect the red lead of the DMM to the red (power) wire on the harness connector. Be aware that wire colors might differ based on your vehicle model, so refer to the wiring diagram for your specific model.
- Switch the ignition key to the “On” position. The DMM should show a reading between 5 and 13 volts. Refer to your vehicle repair manual for the reference voltage value for your model. If the reference voltage is below the expected value or zero, inspect the wire and connector for damage or loose terminals. If necessary, check your car’s computer.
- Turn off the ignition and reconnect the crankshaft position sensor to the harness connector.
- Set the DMM to a low DC voltage range capable of reading millivolts.
- Connect 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.
- Connect 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 needed, align your results with the specifications laid out in your vehicle’s repair manual.
If your Digital Multimeter (DMM) is capable of interpreting Duty Cycle signals, depending on your vehicle’s system, you might also be able to detect a crankshaft signal.
- For this, back probe the signal wire on the sensor and connect the black lead of the DMM to the ground.
- Then, switch the DMM to the Duty Cycle function.
- Get someone to crank the engine for you.
- In case the Crankshaft Position (CKP) sensor fails to generate a duty cycle signal, it could be faulty.
Always ensure to consult your vehicle repair manual for specific instructions and guidelines when testing the crankshaft position sensor for your specific vehicle model.