What a crank sensor does and why it fails

Your crank sensor tells your engine's computer where the crankshaft is and how fast it's spinning. The engine uses this information to time the spark plugs and fuel injectors. When a crank sensor fails, your car won't start, stalls while driving, or runs so poorly you'll notice it when ready.

Crank sensors fail because they wear out over time—they're exposed to heat, vibration, and engine oil. A failed sensor doesn't always trigger a check engine light right away, which is why you may need to test it yourself before taking it to a mechanic. The sensor sits near the crankshaft, usually underneath the engine or near the timing cover, so accessing it requires some basic tools and space to work.

Key Takeaways

  • A crank sensor that's failing will cause hard starting, stalling, or rough idle, and you can narrow down the problem by checking for a check engine light first.
  • You can test a crank sensor with a multimeter by measuring resistance and AC voltage, though the exact steps depend on whether your sensor is inductive or Hall-effect type.
  • The sensor's location varies by vehicle—check your owner's manual or a repair guide for your specific make and model before you start.
  • A resistance reading outside the manufacturer's range or zero AC voltage while the engine cranks usually means the sensor has failed and needs replacement.

Locate the crank sensor on your vehicle

The crank sensor's location depends on your car's make, model, and year. On most vehicles, it sits near the crankshaft pulley at the bottom front of the engine, or near the timing cover. Some cars have it mounted on the transmission bell housing. Your owner's manual will show the exact location and may include a diagram.

If you don't have the manual, search online for "[your year, make, model] crank sensor location" and you'll find photos or videos showing where it is on your specific vehicle. Once you know where it is, you may need to remove a wheel, lower the car on a jack, or remove a plastic cover to reach it. Write down the sensor's part number or take a photo before you disconnect it—this helps you order the right replacement if testing shows it's bad.

Check for a check engine light and read the code

Before you test the sensor itself, check whether your car's computer has already flagged a problem. Turn the ignition to the "on" position without starting the engine. If a check engine light is on, you can read the code using an OBD-II scanner (a handheld device that plugs into the diagnostic port under your dashboard). Crank sensor codes usually start with P0016, P0335, P0336, or P0337, depending on the fault.

If you don't own a scanner, many auto parts stores will read the code for free. A code pointing to the crank sensor doesn't may provide the sensor itself is bad—it could be a wiring problem or a connector that's loose—but it tells you where to focus your testing. If there's no check engine light, you'll need to test the sensor directly with a multimeter.

Test the sensor with a multimeter

A multimeter is a handheld meter that measures voltage and resistance. You'll need one to test whether the crank sensor is producing a signal. Set your multimeter to the resistance setting (ohms). Disconnect the sensor's electrical connector and touch the multimeter probes to the sensor's terminals. The resistance reading should fall within the range listed in your vehicle's service manual—typically between 200 and 900 ohms, though this varies by manufacturer.

If the reading is zero, infinity, or far outside the expected range, the sensor's internal coil is damaged and it needs to be replaced. If the resistance is within range, reconnect the sensor and move to the voltage test. A sensor can have normal resistance but still fail to produce a signal when the engine is running, so this step alone doesn't always tell you the whole story.

Measure AC voltage while the engine cranks

This test shows whether the sensor is actually generating a signal. Set your multimeter to AC voltage (not DC). Reconnect the sensor's electrical connector and touch the multimeter probes to the sensor's signal wire and ground wire. Have someone crank the engine while you watch the meter. A working inductive crank sensor should produce between 0.5 and 5 volts AC while cranking.

If the meter reads zero or stays flat while the engine is cranking, the sensor is not producing a signal and has likely failed. If you see voltage fluctuating, the sensor is working. Some multimeters are slow to respond to AC signals, so a reading that jumps around or seems unstable may actually be normal—what matters is that you see some voltage change, not a flat line. If you're unsure, repeat the test a second time or have a mechanic confirm with a scope.

Check the wiring and connector

Before you assume the sensor is bad, inspect the connector and wiring. Disconnect the sensor's electrical connector and look inside for corrosion, bent pins, or moisture. Corrosion looks like a white, green, or blue crusty buildup. If you see it, you can sometimes clean the connector with electrical contact cleaner and a small brush, then reconnect it and retest.

Also check the wiring harness for cuts, pinches, or damage. If the wire is damaged, it will need to be repaired or replaced before you replace the sensor. A loose or corroded connection can cause the same symptoms as a failed sensor, so this step can save you the cost of an unnecessary replacement. If the connector and wiring look clean and intact, and your resistance and voltage tests showed the sensor is bad, it's time to replace it.

Know when to replace versus repair

Crank sensors cannot be repaired—they must be replaced. Once the internal coil fails or the sensor stops producing a signal, there's no fix short of swapping it out. Replacement sensors are inexpensive (usually $50 to $200 for the part) and the labor to install one typically runs $100 to $300 at a shop, depending on how hard it is to reach on your vehicle.

If you're comfortable working on cars, you can replace it yourself: disconnect the old sensor, unbolt it, install the new one, bolt it down, and reconnect the connector. The whole job usually takes 30 minutes to an hour. After installation, clear the check engine code using your scanner or by disconnecting the battery for 15 minutes, then start the engine and confirm the light doesn't come back on.

Frequently Asked Questions

Can a bad crank sensor cause a no-start condition?

Yes. If the sensor isn't sending a signal, the engine's computer won't know when to fire the spark plugs or inject fuel, so the engine won't start at all. You may hear the starter motor turn over, but the engine won't catch. This is one of the most common symptoms of a failed crank sensor.

What's the difference between an inductive and Hall-effect crank sensor?

An inductive sensor generates its own AC voltage signal as the crankshaft spins past it. A Hall-effect sensor uses a magnet and semiconductor to produce a digital on-off signal. Testing methods are slightly different—inductive sensors produce AC voltage, while Hall-effect sensors produce DC voltage. Your service manual will tell you which type your vehicle has.

Will disconnecting the battery clear a crank sensor code?

Disconnecting the battery for 15 minutes will clear the code temporarily, but it will come back if the sensor is still bad. This is useful after you replace the sensor to reset the computer, but it's not a permanent fix for a failed sensor. If the code returns within a few days of driving, the sensor replacement didn't solve the problem and you should have the wiring and connector checked again.

Can I drive with a failing crank sensor?

Not safely. A failing sensor will cause stalling, hard starting, or loss of power while driving. Stalling in traffic or on a highway is dangerous. If you suspect a crank sensor problem, have it tested and replaced before driving the vehicle regularly. Some cars may limp along on a bad sensor for a short distance, but reliability is unpredictable.

Do I need a special tool to remove the crank sensor?

Usually not. Most crank sensors bolt on with a single bolt or are held in by a clip, and you can remove them with a wrench or socket. Some sensors are tight or in awkward spots, so you may need a sensor socket (a special deep socket with a slot for the wiring) or a small ratchet. Check your service manual or a repair video for your specific vehicle to see what tools are needed.