Symptoms of a Bad Crankshaft Sensor

The crankshaft Sensor

The crankshaft sits inside the engine and rotates. It’s attached to the connecting rods and pistons, so while the engine runs, the piston’s linear motion turns the crankshaft. This creates a rotational force that moves the vehicle.

Shop now for crankshaft position sensors

The crankshaft position (CKP) sensor is responsible for measuring the speed and position of the crankshaft. A notched or toothed wheel on the crankshaft or harmonic balancer sends a signal to the engine’s computer showing its position.

The computer uses the information from the CKP sensor to determine fuel injection and spark timing. The CKP signal may also be used for other systems, such as variable valve timing. All vehicles built after 1996 also use the CKP sensor to determine engine misfires.

The CKP sensor is often located at the front bottom of the engine. Although this can vary by vehicle, so it’s best to check your service manual to confirm the location.

Common Crankshaft Sensor Symptoms

The CKP sensor feeds information to the powertrain control module (PCM). When it goes bad and sends out faulty signals, you can expect a wide range of problems. Here are some of the most common.

Check Engine Light

When the signal between the CKP sensor and PCM signal is faulty, the check engine light comes on. In fact, this can be one of the very first signs that something is wrong, before any symptoms are noticed.

If the check engine light is on, you should be able to read the diagnostic trouble codes (DTC) that were set in the system. You may see a code that references the camshaft position, crankshaft position, or the camshaft or crankshaft position sensors. A simple internet search of the code will provide details about the error.

Engine Refuses to Start

For a gas engine to run correctly, it needs three things: a spark, a balanced air-fuel ratio, and compression. If the CKP sensor goes bad, the PCM won’t know when to fire the spark plugs and when to operate the fuel injectors.

Because of this malfunction, the engine may become starved of fuel or may lack the spark it needs to run. Therefore, it may become difficult or impossible to start the engine.

Engine Stalling

The CKP sensor can cause an erratic signal as it fails. When the information becomes distorted, the engine may stall because of issues in the spark or fuel functions. If the engine stalls and won’t restart, you could be left stranded.

Rough-Running Engine

As previously discussed, a bad CKP sensor leads to miscalculation of the fuel injector operation and timing of the spark. If the engine doesn’t stall as a result of this problem, it could run rough.

You may even deal with misfires, which feel like a stumble or shaking sensations. If the vehicle is under a load, the shaking will likely be more noticeable. You shouldn’t continue driving your vehicle with a misfire, as it can lead to other more costly damage, such as to the catalytic converter.

Reduced Fuel Economy

If the engine isn’t getting the proper balance of fuel and air, or if it’s running rough, fuel economy will drop. The issue can be further exacerbated by a faulty CKP sensor inhibiting fuel-saving functions. This problem can stop the cylinder deactivation and variable valve timing systems from working, leading to wasted fuel.

Shop now for crankshaft position sensors

If the car doesn’t start at all, you won’t have to worry about driving it. This is a common problem when the CKP sensor fails.

If the vehicle starts, you may feel tempted to drive, but you shouldn’t. Intermittent CKP issues can quickly lead to stalling and the inability to restart the car. You could end up stranded away from home, waiting for roadside assistance.

The best option is to diagnose and replace the faulty sensor at the first sign of trouble.

Diagnosing a Bad Crankshaft Position Sensor

If you suspect there’s an issue with the crankshaft position sensor, start by visually inspecting it. If there are any cracks or damage, the sensor should be replaced. There could also be a corroded or loose connector that can be easily repaired.

It’s also important to look at the gap between the sensor tip and reluctor ring—the toothed ring on the crankshaft that interacts with the CKP for precise timing. It must be a precise measurement that’s listed in your vehicle’s service manual.

Use the service manual to find the proper testing procedures for your vehicle. If your vehicle has a pick-up coil sensor, check the resistance. Usually, if the internal resistance measures 200 to 1,000 ohms, the sensor is working normally. If you get a 0 ohms value, it has a short circuit. Otherwise, an M ohm reading indicates some type of interruption.

If you don’t know which design the crankshaft position sensor uses, do not use an ohmmeter for testing. The voltage used during testing can destroy a Hall generator. Hall-type sensors need to have the ground signal tested. You should also check the sensor signal with an oscilloscope.

Shop now for OBD code scanners

Finally, advanced code scanners also can troubleshoot the crankshaft position sensor. Monitoring the signal of the sensor is helpful, especially during intermittent issues. You may see the signal drop to zero, indicating it’s time for a replacement.

Replacing a Crankshaft Sensor

Once you’ve determined that the crankshaft position sensor is bad, it’s time to replace it. Here are some steps to follow if you want to do it on your own.

1. Gather your tools. You will need a floor jack, jack stands, the new crankshaft position sensor, plus a ratchet and socket set (1/4” or 3/8”).
2. Jack the vehicle up high enough to reach the crankshaft position sensor.
3. Secure the vehicle on jack stands.
4. Disconnect the electrical connector from the engine’s wiring harness.
5. Locate and remove the CKP sensor. It is usually on the front of the engine near the crankshaft pulley. Use your socket and ratchet to remove the hold-down bolt.
6. Gently twist to remove the sensor.
7. Lubricate the O-ring on the new sensor for easier installation.
8. Gently twist the new CKP sensor into its place.
9. Secure the bolt and tighten it to the factory specs listed in the service manual.
10. Connect the new sensor.
11. Remove the jack stands and gently lower the vehicle.

Now it’s time to turn off the check engine light. Use your compatible scanner to clear the trouble code. The check engine light should remain off if the problem has been resolved. If it comes back on, you may have other issues.

Shop now for crankshaft position sensors

Tell your friends: