What a Crank Position Sensor Does and Why It Fails

A crank position sensor tells your engine's computer where the crankshaft is at any given moment. The computer uses that signal to time the spark plugs and fuel injectors. When the sensor fails, your engine won't start, runs rough, stalls without warning, or throws a check-engine light. You'll see the code P0335 or similar in your diagnostic reader.

The sensor sits near the crankshaft, usually on the front, side, or rear of the engine block depending on your vehicle. It reads a toothed ring on the crankshaft as it spins. Over time, the sensor's electronics wear out or the connector corrodes, and the signal becomes weak or stops altogether. Replacement is straightforward on most vehicles and costs between $150 and $400 in parts and labor at a shop, though the part itself is often $50 to $150.

Key Takeaways

  • The crank position sensor mounts to the engine block near the crankshaft and can be reached without removing major components on most vehicles.
  • You will need a socket set, a wrench, a screwdriver, and a new sensor matched to your exact year, make, and model.
  • Disconnect the negative battery terminal before you start to prevent accidental short circuits.
  • The sensor usually bolts on with one or two fasteners and unplugs with a straightforward connector pull; installation reverses the removal steps.
  • After installation, clear the check-engine light with a diagnostic scanner or by disconnecting the battery for ten minutes.

Locate the Sensor on Your Engine

The crank position sensor location varies by manufacturer. On many Ford, Chevrolet, and Dodge vehicles, it sits on the front of the engine block near the crankshaft pulley. On others, it mounts to the side or rear. Your owner's manual or a repair manual for your specific year and model will show the exact spot. You can also search online for "[your year, make, model] crank position sensor location" and find diagrams or videos.

Once you know where it is, look at the engine from above and from the sides to see how much room you have to work. Some sensors are straightforward to reach; others require you to remove the wheel well liner or a plastic cover. If major components are in the way, you may need a lift or ramps to get underneath safely. Never work under a car supported only by a jack.

Gather Tools and the Correct Replacement Part

You will need a socket set (usually 8 mm to 15 mm), an adjustable wrench, a Phillips or flat-head screwdriver depending on your fasteners, and a new crank position sensor. The sensor must match your vehicle's year, make, model, and engine size exactly. Buy it from an auto parts store, online retailer, or your vehicle's dealer. Bring your vehicle identification number (VIN) or license plate to the parts counter so they can confirm the right part.

You may also want a small flashlight or headlamp, a container for small bolts so you don't lose them, and a clean rag. Some sensors come with a new connector or gasket; check the box before you start. If the old connector is damaged, you may need to buy a replacement connector separately.

Disconnect the Battery and Remove the Old Sensor

Open your hood and locate the negative battery terminal (marked with a minus sign or black cable). Loosen the nut on the terminal with a wrench and slide the cable off. This prevents accidental electrical shorts while you work. Wait a few minutes before touching anything electrical on the engine.

Find the crank position sensor and unplug the electrical connector by squeezing the tab or pulling straight back, depending on the design. Take a photo of the connector orientation with your phone so you remember how it goes back in. Then unbolt the sensor from the engine block using your socket set or wrench. Most sensors have one or two bolts. Keep the bolts in your container. Slide the sensor straight out and set it aside.

Install the New Sensor and Reconnect Everything

Slide the new sensor into the mounting hole and align it the same way the old one sat. Hand-tighten the bolts first, then use your socket set to snug them down firmly but not so hard that you crack the sensor body. Most crank position sensors need only 15 to 25 foot-pounds of torque; check your repair manual if you have a torque wrench.

Plug the electrical connector back in until you hear or feel it click. Make sure the connector is fully seated and not loose. Reconnect the negative battery terminal by sliding the cable back on and tightening the nut. Do not overtighten; hand-tight plus a quarter turn is enough.

Clear the Check-Engine Light

Start the engine and listen for any unusual sounds. The check-engine light may stay on for a few minutes while the computer runs its first test cycle. If it goes out on its own after a few minutes of driving, the job is done. If it stays on, you can clear it yourself with a diagnostic scanner (available at auto parts stores for $25 to $100) or by disconnecting the negative battery terminal for ten minutes, which will reset the computer.

If the light comes back on after you clear it, the new sensor may be faulty, the connector may not be fully seated, or another problem may be present. Recheck the connector and the bolt tightness. If the light persists, take the vehicle to a shop and have them read the code to see what is wrong.

When to Call a Professional

If the sensor is in a tight spot that requires removing the wheel well, intake manifold, or other major components, a shop may be faster and safer. If you don't have a socket set or feel uncomfortable working under the hood, a technician can do the job in under an hour. If the new sensor doesn't solve the problem, a shop can diagnose whether the issue is a wiring fault, a bad connector, or a computer problem that needs different repair.

Some vehicles also have a camshaft position sensor in addition to the crank sensor. If your check-engine light returns after replacing the crank sensor, the problem may be the cam sensor instead. A diagnostic scanner will tell you which sensor is actually failing.

Frequently Asked Questions

Can I drive with a bad crank position sensor?

No. A failed crank sensor will prevent your engine from starting or cause it to stall while driving. Continuing to drive is unsafe and can damage the catalytic converter. Replace it as soon as the problem appears.

How long does it take to replace a crank position sensor?

On most vehicles, removal and installation take 30 minutes to an hour if the sensor is straightforward to reach. If it requires removing other components, the job can take two to three hours. A shop will charge one to three hours of labor depending on location and difficulty.

What if the new sensor doesn't fix the problem?

The wiring harness or connector may be damaged, the computer may have a fault, or a different sensor may be the real cause. Use a diagnostic scanner to read the exact code. If the code is still P0335 after replacement, the wiring is likely the problem. If the code changes, a different sensor may need replacement.

Do I need to reset the computer after replacing the sensor?

The computer will reset itself after a few minutes of driving. You can also clear the code manually with a scanner or by disconnecting the battery for ten minutes. Resetting is not required for the sensor to work, but clearing the light confirms the repair was successful.

Can I replace the crank sensor myself if I've never done it before?

Yes, if you have basic tools and the sensor is straightforward to reach on your vehicle. Watch a video for your specific year and model first. If the sensor is buried under other parts or you feel unsure, a shop is the safer choice and will cost less than a mistake.