How To Test 3 Wire Crank Sensor With Multimeter (4 Step Guide)

What You Need To Know About How To Test 3 Wire Crank Sensor With Multimeter

The crank shaft position sensor as you know is usually attached to the engine’s block facing the actual crankshaft. It has the primary purpose of collecting readings that will ensure that the Engine Control Unit (ECU) is aware of the crankshafts rotation position.

It also serves the purpose of determining when to fire the ignition coil and injection point in communication with the ECU.

This sensor can at times malfunction. When this happens the engine lights will typically be the first warning - try not to ignore this issue for too long and follow your cars manual. This is also typically followed by other additional symptoms such as a fail start, backfiring causing a stalling vehicle or unusual engine vibrations that can be easily felt from the driver’s seat.

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All of these symptoms above are typical of a failed or failing crank shaft position sensor. In this guide we will investigate all the various ways you can go about testing your vehicle’s crank sensor to make sure that it is still fully functional.

What makes up the 3 wire crank sensor

Typically if you observe a 3 wire crankshaft sensor from the view point of the electrical termination points. You will find that it has 3 terminals (hence the name).

As you can see from the image above, there is a GND (Ground) – Signal – Power.

Generally when measuring with a multimeter between the signal and ground you should get a voltage that is approximately 4.8 to 5.5 V depending on crank shaft position sensor.

Whilst the Power-to-Ground voltage should give you something very close to the voltage as seen across the battery terminals, which is something around 12 V.

Another very interesting consideration is that on newer vehicles you can typically expect to find two crankshaft sensors. One on the intake camshaft and the other by the exhaust.

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Depending on the year and model of your vehicle, you could also only have one. Check the user manual and the car’s engines spare parts to ensure that all crank shaft position sensors have been taken into consideration for your specific vehicle.

Equipment You’ll Need To Learn How To Test 3 Wire Crank Sensor With Multimeter

In order to successfully test whether your 3 wire crank sensor with a multimeter actually works you will need a couple of things below.

• Digital Multimeter
• Pin leads and crocodile leads
• Oscilloscope (optional)
• A Partner (This will require 2 people)

4 Steps Guide On How To Test 3 Wire Crank Sensor With Multimeter

Step 1 – Test the connector

This step requires you to remove the crankshaft sensor from the interconnectors.

Turn on the ignition of the vehicle, such that the dashboard lights go on. Do not crank the engine this test serves the primary purpose to ensure that power is actually being transmitted to the crankshaft position sensor.

Now using your multimeter find the 3 different pins (i.e. GND – POWER – SIGNAL pins). Measure the voltage between these pins.

You should be getting around 4.5 – 5.5 V for the SIGNAL – GND measurement and about 12V for the POWER – GND measurement.

Step 2 – Connect the crankshaft position sensor to the 3 pin connector

Now with the car remaining in the position of having the dash light on, connect the crankshaft position sensor to it’s connector.

Use your pin leads to work your way through the back of the connector with the multimeter installed and start measuring the voltage again.

What you want to see are similar ranges in voltage as was experienced in Step 1. If this is the case then you know that your crankshaft position sensor is indeed getting power and is functional when in a connected position.

Step 3: Remove ASD Relay and crank the throttle

With the crankshaft position sensor connected. Turn off the vehicle and remove the ASD relay

We remove the Automatic Shutdown Relay (ASD) relay to prevent the car from starting. If you are struggling to identify were this relay is to be found, consult your car’s parts list or user manual.

Once the ASD has been removed, ask your partner to crank the vehicle, whilst you are measuring with the multimeter between SIGNAL and GND.

As the vehicle is cranked you should see a drop in voltage from the original 4.5 to 5.5 V down to about +/-0.5 V.

Theoretically as you crank your vehicle the hall effect sensor should cause voltage to drop down to zero, however due to a surge of current to ground there will be a slight voltage difference that the multimeter will pick up.

This slight difference of about +/- 0.5 V, whilst cranking is generally ok. This step proves the proper functioning of the hall effect portion of the crank shaft position sensor.

If you are recording voltages higher the 1V or if the voltage does not change whilst cranking the vehicle, this means that you have a defective sensor that needs urgent replacement.

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Advanced - Step 4: Use an oscilloscope to see the voltage spikes

This step is a bonus step, using your oscilloscope, you can attach the test leads to your crankshaft sensor.

Place the ASD relay back and crank the engine to start the car. Let the car sit on idle and you should see a drop in voltage from 5V down to about 120 mV or so.

The key thing to pick up here is to ensure that your measurement period is consistent and the voltage amplitudes and frequencies are the same for each cycle.

The reason we use an oscilloscope for this specific step is because your general digital multimeter will take the average measurement over the period.

So you will generally see something around 120 – 240 mV on your multimeter.

However you will not appreciate how this value was derived. It is important also to note that the initial starter current during the transient phase of starting up the vehicle could reach between 600 and 800 amps.

That is that – if you following these steps you should be able to test 3 wire crank sensor with multimeter quite easily and simply.

Final Thoughts On How To Test 3 Wire Crank Sensor With Multimeter

As you can see learning how to test 3 wire crank sensor with multimeter requires a little bit knowledge and know how. Please always ensure that you take the safety precautions seriously.

Be vigilant and focused and record your multimeters readings so that you can refer to them at a later stage. I had a lot of fun creating this guide and I hope it has been helpful