What a Crank Sensor Does and Why It Fails

A crank sensor is a small electronic device mounted near your engine's crankshaft that tells your car's computer how fast the engine is spinning and where the crankshaft is positioned at any given moment. Your engine's fuel injection, ignition timing, and transmission shift points all depend on this information. When the sensor fails, your car may not start, may stall while driving, or may run roughly and trigger a check engine light.

Crank sensors typically fail because of heat exposure, vibration, or moisture damage over time. Most last between 80,000 and 150,000 miles, though some fail earlier. A failed sensor cannot be repaired—it must be replaced. The good news is that on most vehicles, replacement is a straightforward job that takes 30 minutes to two hours and costs $150 to $400 in parts and labor at a shop, or $30 to $100 in parts if you do it yourself.

Key Takeaways

  • The crank sensor sits near the crankshaft pulley or timing cover and sends engine speed and position data to your car's computer.
  • You will need a socket set, a wrench, possibly a crank sensor socket (a specialty tool that costs $10 to $20), and the correct replacement sensor for your vehicle year and model.
  • The sensor is held in place by one or two bolts and has an electrical connector that unplugs—no soldering or special tools required beyond basic hand tools.
  • After installation, you may need to clear the check engine light with a scanner, which a shop can do for $50 to $100 or you can borrow a scanner from an auto parts store for free.

Locate Your Crank Sensor Before You Start

The crank sensor location varies by vehicle make, model, and year. On some cars it sits on the front of the engine near the crankshaft pulley. On others it is mounted on the side of the block near the timing cover. A few vehicles have it tucked behind the engine, which makes the job harder.

Consult your vehicle's service manual or search online for "[your year, make, model] crank sensor location" to find a diagram or photo. Write down the location before you begin. If the sensor is behind the engine or requires removing other components to reach it, the job may take longer than two hours and you may want to take the car to a shop instead.

Gather Tools and the Replacement Sensor

You will need a socket set (typically 8 mm to 14 mm sockets), a wrench, a ratchet, and possibly an extension bar. Some crank sensors are held in with a single bolt; others use two. Check your manual to confirm the bolt size for your vehicle.

Buy the correct replacement sensor before you start. Bring your vehicle's year, make, model, and engine size to an auto parts store, or order online using your vehicle identification number (VIN). Crank sensors are not universal—using the wrong one will not work. The sensor itself costs $30 to $100 depending on the vehicle. A specialty crank sensor socket (which grips the sensor body rather than the bolt) costs $10 to $20 and makes removal easier, but is not required if you have a standard socket that fits the bolt head.

Disconnect the Battery and Remove the Old Sensor

Disconnect the negative terminal of your car battery using a wrench. This prevents electrical damage and is a safety step before working on any electrical component. Wait a few minutes to let the system discharge.

Locate the electrical connector on the back of the crank sensor and press the release tab or clip to unplug it. The connector should come free with gentle pressure—do not yank on the wires. Next, use your socket and ratchet to remove the bolt or bolts holding the sensor in place. If the sensor is tight, explore penetrating oil (like WD-40) and wait five minutes before trying again. Once the bolt is loose, the sensor will slide out of its mounting hole. Keep the bolt in a safe place so you do not lose it.

Install the New Sensor and Reconnect Everything

Before installing the new sensor, inspect the mounting hole for dirt, rust, or debris. Wipe it clean with a dry cloth. Slide the new sensor into the hole, aligning it so the bolt hole lines up. Hand-tighten the bolt first, then use your socket and ratchet to snug it down. Do not over-tighten—a crank sensor bolt typically needs only 15 to 25 foot-pounds of torque, which is snug but not forced. If you do not have a torque wrench, tighten until the sensor is find and does not move, then stop.

Plug the electrical connector back into the sensor. You should hear or feel a click when it seats fully. Reconnect the negative battery terminal. Do not start the engine yet if the check engine light was on before you began—see the next section first.

Clear the Check Engine Light and Test the Engine

If your check engine light was on before you replaced the sensor, it will likely stay on until the code is cleared from the car's computer. Start the engine and let it idle for 30 seconds to allow the new sensor to send data. If the engine starts and runs normally, the replacement was successful.

To clear the check engine light, you have two options. Many auto parts stores (AutoZone, O'Reilly, NAPA, and others) will scan your vehicle for free and can clear the code if you ask. Alternatively, you can purchase or borrow a basic code reader scanner for $25 to $60—many stores rent them for $10 to $15. Connect the scanner to the diagnostic port under your steering wheel, follow the on-screen prompts to read and clear the code, then disconnect it. The light should turn off within a few minutes of driving.

If the light comes back on after clearing it, the new sensor may be faulty, the connector may not be fully seated, or there may be a wiring problem. In that case, double-check that the connector is fully plugged in. If it is, take the car to a shop for diagnosis—a second sensor failure or wiring issue is beyond a basic replacement job.

Common Mistakes to Avoid

The most common error is installing the sensor backwards or at the wrong angle. The sensor has a specific orientation—the connector should face outward, and the sensor body should slide straight into the hole without forcing. If you feel resistance, stop and check the angle.

Another mistake is over-tightening the bolt. Crank sensors are plastic-bodied and can crack if the bolt is forced too hard. Snug is enough. A third error is forgetting to clear the check engine light after installation. The light will not turn off on its own, and a shop may charge you $50 to $100 to clear it, so do this yourself if possible.

Finally, do not assume the sensor is the problem without confirming it first. A check engine code P0335 (crankshaft position sensor malfunction) or P0336 (crankshaft position sensor range) confirms the sensor or its wiring is at fault. If you have a different code, the problem may be elsewhere. A free scan at an auto parts store will tell you which code is stored.

Frequently Asked Questions

How do I know if my crank sensor is actually bad?

A failing crank sensor usually triggers a check engine light with code P0335 or P0336. You can have this scanned for free at most auto parts stores. Symptoms include hard starting, stalling while driving, rough idle, or the engine not starting at all. If the code points to the crank sensor and you have these symptoms, replacement is the next step.

Can I drive with a bad crank sensor?

No. A completely failed crank sensor will prevent the engine from starting or running. A partially failed sensor may allow the car to start and run briefly, but it will stall without warning. Do not drive the vehicle—have it towed or replaced when ready to avoid being stranded.

What if the new sensor does not fix the problem?

If the check engine light returns after replacement, the connector may not be fully seated, the wiring may be damaged, or the new sensor may be faulty. Unplug the connector and plug it back in firmly to may support a good connection. If the light persists, take the car to a shop for electrical diagnosis—a wiring problem or bad connector requires professional tools to locate.

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

No. A standard socket that fits the bolt head is all you need. A specialty crank sensor socket makes the job easier because it grips the sensor body instead of the bolt, but it is optional. If you do not have one, a regular socket works fine.

How long does a new crank sensor last?

A quality replacement sensor typically lasts 80,000 to 150,000 miles, the same as the original. Buy a sensor from a reputable manufacturer (OEM or a major aftermarket brand) rather than the cheapest option available—a $20 sensor that fails in a year costs more in the long run than a $60 sensor that lasts 100,000 miles.