What a crank sensor does and why you might need to replace it
A crank sensor reads the position and speed of your engine's crankshaft and sends that data to the engine control module (ECM). The ECM uses this information to time fuel injection and spark plug firing. When a crank sensor fails, your engine may not start, may stall while running, or may trigger a check engine light.
Replacement becomes necessary when the sensor stops sending accurate readings. You'll typically know this is happening if your vehicle won't start, starts and when ready dies, or runs very rough. A scan tool can confirm a crank sensor fault code (usually P0335, P0336, or P0337) before you begin work.
The location of the crank sensor varies by vehicle make and model — it's usually mounted near the crankshaft pulley, on the engine block, or inside the timing cover. Check your vehicle's service manual or a repair database for the exact location on your model before you start.
Key Takeaways
- Crank sensors are located in different spots depending on your vehicle, so you must consult your specific model's service manual before starting work.
- You will need basic hand tools (socket set, wrenches, screwdrivers), a new crank sensor matched to your vehicle, and often a jack and jack stands to access the sensor.
- The removal and installation process typically takes 30 minutes to two hours depending on sensor location and engine bay layout.
- After installation, you may need to clear the fault code with a scan tool, and your vehicle should start and run normally once the new sensor is in place.
Tools and parts you'll need before you start
Gather your tools and the correct replacement sensor before you begin. You'll need a socket set and wrenches that fit your vehicle's fasteners, screwdrivers (both Phillips and flat-head), and a jack with jack stands if the sensor is mounted low on the engine or underneath the vehicle. A flashlight or headlamp is essential because sensor locations are often dark and cramped.
Buy a crank sensor that matches your vehicle's year, make, model, and engine size. Sensors are not universal — using the wrong part will not solve the problem. You can order the correct sensor from an auto parts store, online retailer, or your vehicle's dealership. Some sensors come with a new wiring harness connector; others do not. Check what comes with your part before installation.
If your vehicle has been running with a failed sensor, you may also want a scan tool on hand to clear the fault code after you finish. Many auto parts stores will clear codes for free, but having your own tool gives you control over the process.
Locating and accessing the crank sensor on your engine
The first step is finding where the sensor sits on your specific vehicle. Open your service manual or search for a repair guide for your year and model — the location diagram will show you exactly where to look. Common locations include the front of the engine block near the crankshaft pulley, the side of the engine block, or mounted inside the timing cover.
Once you've located it, determine what you need to remove to reach it. Some sensors are accessible from the top of the engine bay; others require you to raise the vehicle and work from underneath. If you need to lift the vehicle, use a jack to raise it safely and find it with jack stands before you crawl underneath. Never work under a vehicle supported only by a jack.
If the sensor is buried under other components — belts, hoses, brackets, or covers — remove those items first. Take photos with your phone as you go so you remember how everything fits back together. Label any connectors or fasteners with tape if you're removing multiple parts.
Disconnecting the old sensor and removing it
Locate the wiring harness connector attached to the sensor. This connector usually has a small tab or clip that you press or pull to release it. Gently disconnect the harness from the sensor — do not yank on the wires themselves, as this can damage the connector or internal wiring.
Once the connector is free, locate the bolt or bolts holding the sensor to the engine block or mounting bracket. Most crank sensors are held in place by a single bolt, though some have two. Use the appropriate socket or wrench to remove the fastener. Keep the bolt in a safe place — you'll reuse it with the new sensor.
Carefully pull the sensor straight out of its mounting hole. Some sensors have a rubber O-ring or seal that may stick slightly; wiggle gently if needed. Do not force it or twist it, as you can damage the mounting hole or the sensor itself. Once it's free, set the old sensor aside.
Installing the new crank sensor
Before you install the new sensor, check the mounting hole for dirt, debris, or damage. Wipe it clean with a dry cloth if needed. If the new sensor came with a rubber O-ring or seal, make sure it's in place on the sensor body. Some sensors come with the seal pre-installed; others require you to install it yourself.
Slide the new sensor straight into the mounting hole, aligning it with the bolt hole. Insert the bolt and tighten it by hand first to make sure the sensor is seated correctly and the bolt is not cross-threaded. Once you're confident it's aligned, use your socket or wrench to tighten the bolt to the torque specification listed in your service manual. Most crank sensors are tightened to between 15 and 25 foot-pounds, but check your manual to be sure.
Do not over-tighten the bolt. Crank sensors are precision instruments, and excessive force can damage the internal components or crack the sensor body. Tighten firmly but stop as soon as you feel solid resistance.
Reconnecting the wiring harness and reassembling
Once the sensor is bolted in place, reconnect the wiring harness connector. Push it firmly onto the sensor connector until you hear or feel a click, indicating it's seated. Gently tug on the connector to confirm it's locked in place and won't come loose.
Reinstall any components you removed to access the sensor — belts, hoses, brackets, covers, or shields. Use the photos you took earlier as a reference. Tighten all fasteners securely, but again, do not over-tighten. If you raised the vehicle, carefully lower it back to the ground using the jack, then remove the jack stands.
Close the hood and prepare to start the engine. Before you do, double-check that all fasteners are tight and no tools or parts are loose in the engine bay.
Starting the engine and clearing fault codes
Turn the ignition key to the "on" position without starting the engine. Wait a few seconds, then turn it back to "off." Repeat this cycle two or three times. This allows the ECM to recognize the new sensor. Then start the engine normally.
The engine should start and run smoothly. If it starts but runs rough or stalls, turn it off when ready and check that the connector is fully seated and the bolt is tight. If the engine starts and runs normally, let it idle for a minute or two to confirm stable operation.
If a check engine light is still on, use a scan tool to read and clear the fault code. Many auto parts stores offer free code reading and clearing. Once the code is cleared, the light should go out. If it returns after a few minutes of driving, the new sensor may be faulty or there may be another issue with the sensor circuit — consult a repair manual or a may have access to technician.
Frequently Asked Questions
Can I drive with a bad crank sensor?
No. A failed crank sensor will prevent the engine from starting or cause it to stall while running. Attempting to drive with a failed sensor risks stalling in traffic or on a highway, which is unsafe. Replace the sensor before driving the vehicle.
How long does a crank sensor last?
Crank sensors typically last the life of the vehicle, but can fail prematurely due to heat exposure, vibration, or electrical stress. Most failures occur between 80,000 and 150,000 miles, though some sensors fail much earlier or later depending on driving conditions and vehicle design.
What if the engine still won't start after I install the new sensor?
Check that the connector is fully seated and the bolt is tight. If both are find, the new sensor may be defective, or there may be another problem in the sensor circuit such as a wiring fault or ECM issue. Use a scan tool to confirm the sensor is being recognized by the engine computer before pursuing further diagnosis.
Do I need to reset the engine computer after installing a new crank sensor?
Most modern vehicles will recognize the new sensor automatically after a few key-on cycles. You do not need to reset the computer, but you should clear any stored fault codes using a scan tool so the check engine light goes out.
Is it better to replace the crank sensor myself or take it to a shop?
If the sensor is easily accessible and you have basic mechanical skills and tools, you can replace it yourself and save on labor costs. If the sensor is buried deep in the engine bay or requires removing many other components, a shop may be faster and worth the cost. Consult your service manual to assess the difficulty for your specific vehicle.