5 Symptoms of a Bad Crankshaft Position Sensor (and Replacement Cost)

Is your engine sputtering, stalling, or not starting? Maybe your engine is shaking and you’re feeling it through your steering wheel. A faulty crankshaft position sensor could be to blame.

Here’s how to recognize the common symptoms of a faulty crankshaft position sensor along with how much it’s going to cost to replace it. Hint: It’ll be a lot cheaper now than if you were to ignore it.

What Is a Crankshaft Position Sensor?

A crankshaft position sensor is a specialty device found on virtually all modern internal combustion engines, dedicated to providing a vehicle’s primary control module (ECM or PCM) with feedback pertaining to engine speed.

This sensor is generally mounted within the engine block or timing cover. Alternatively, some crankshaft position sensors can be found affixed to an engine’s rear housing, along the point of union for the engine and transmission.

The crankshaft position sensor relies upon magnetism to produce AC pulses as a crankshaft-mounted tone ring spins with every rotation of the crankshaft itself. As each tooth of this tone ring passes before the probe end of the crankshaft position sensor, a magnetic pulse is induced.

The faster an engine’s crankshaft spins, the more frequent these pulses become. In turn, a vehicle’s ECM/PCM detects the frequency of these pulses and calculates this feedback into a precise RPM count.

Crankshaft position sensor feedback is essential to proper engine operation, due to its ability to be used to accurately calculate optimal timing for per-cylinder combustion. Simply put, this feedback is used to determine where, exactly, the crankshaft is within its rotation at any given second during engine operation.

Bad Crankshaft Position Sensor Symptoms

The failure of a vehicle’s crankshaft position sensor is typically accompanied by one or more symptoms, a number of which can negatively impact your vehicle’s driveability. The first meaningful step to resolving issues of the like often involves keying in on these underlying symptoms.

#1 – Illuminated Check Engine Light

The failure of a crankshaft position sensor may, or may not lead to a vehicle’s check engine light turning on, depending upon the circumstances at hand, and the model of vehicle in question.

When the ECM or PCM detects inconsistent or absent signals from the crankshaft position sensor, it triggers the check engine light to alert the driver.

There are a number of diagnostic fault codes, such as P0335 and P0336, that directly correspond to sensor feedback failure.

Other Related Codes: P0016, P0017, P0018, P1345 (Crankshaft/Camshaft Position Sensor Correlation)

#2 – Stalling

Engine stalling is a common and potentially dangerous symptom of a faulty crankshaft position sensor. This occurs because modern engines heavily rely on speed signal feedback to maintain efficient and continuous operation.

When the crankshaft position sensor fails to provide accurate data about the engine’s rotational speed and position, the ECM/PCM struggles to properly time fuel injection and ignition events. As a result, the engine may suddenly lose power and stall, even while driving.

Stalling due to a bad crankshaft position sensor can be particularly hazardous in high-traffic situations or when traveling at higher speeds. If you experience repeated stalling, it’s imperative that you get your vehicle inspected by a mechanic ASAP. Engine stalling can have many causes, all of which need prompt investigation.

#3 – No-Start Condition

Another common symptom of a faulty crankshaft position sensor is the inability to start a vehicle’s engine. In this scenario, despite obvious starter actuation, the engine fails to start and run.

This generally occurs when no engine speed feedback is relayed to the ECM/PCM within the initial seconds of cranking.

Without accurate information about the crankshaft’s position, the engine management system cannot determine the appropriate timing for fuel injection and spark ignition. As a result, the engine may crank continuously but fail to start.

This can be particularly frustrating for drivers, as the problem may seem intermittent. Sometimes the engine might start normally, while other times it refuses to turn over.

#4 – Poor Engine Performance

Assuming a vehicle with a faulty crankshaft position sensor does manage to stay running, it’s highly unlikely that its engine will operate without noteworthy inefficiency. This stems from the fact that accurate feedback relating to engine RPM is essential to achieving optimal combustion timing.

When the crankshaft position sensor provides inaccurate or intermittent data, the ECM/PCM struggles to precisely time fuel injection and ignition events. This can result in a range of performance issues, including rough idling, hesitation during acceleration, misfires, and overall reduced power output.

These performance issues not only affect your driving experience but can also lead to increased wear and tear on engine components if left unaddressed for an extended period.

#5 – Reduced Fuel Economy

A decline in fuel economy is often an overlooked but significant symptom of a failing crankshaft position sensor. Because a vehicle’s operating controllers are reliant upon engine speed signal feedback, fuel economy is prone to tanking in the event of crankshaft position sensor failure.

This is due to the inability of the ECM/PCM to properly time combustion events under such circumstances.

When the engine management system cannot accurately determine the crankshaft’s position, it may default to a “safe” mode, often resulting in a richer fuel mixture than necessary. This overcorrection leads to excessive fuel consumption and decreased efficiency.

While many factors can affect fuel economy, a sudden and persistent drop in MPG, especially when combined with other symptoms, could point to a faulty crankshaft position sensor.

Crankshaft Position Sensor Replacement Cost

The cost of crankshaft position sensor replacement often differs from one vehicle to the next, due to variances in parts costs and labor attributed to such a repair. Those that are mechanically savvy, and own their own set of basic hand tools can often complete such repairs on their own, saving themselves money along the way.

When having a vehicle’s crankshaft position sensor professionally replaced, you can expect to pay between $175-$300.

By contrast, the cost of the sensor itself typically tallies up to $45-$85, thus illustrating the amount of savings that can be had from tackling this repair from a DIY standpoint.

Common Causes of Failure

A vehicle’s crankshaft position sensor can fail for one of several different reasons, some of which tend to be more common than others.

Perhaps the most common culprit of failure is damage to the crankshaft position sensor’s circuitry. It’s not uncommon for sensors of this type to fail at their plugs, failing to provide reliable continuity. Alternatively, a crank position sensor can fail internally, or its wiring harness/pigtail can become pinched or chafed.

It’s also not uncommon for crankshaft position sensors to become damaged during undercarriage debris strikes. Due to the proximity of this sensor to the lower half of a vehicle’s engine, tire casings, and other road litter make formidable opponents to the crank position sensor when struck while in the lane of travel. 

Age and heat also serve as mortal enemies to a vehicle’s crankshaft position sensor. With time, the actual structural body of the crankshaft position sensor can become brittle, making it subject to failure under vibration. Unfortunately, there is little that can be done to prevent this from occurring.

Diagnosing a Faulty Sensor

One of the simplest ways to diagnose a faulty crankshaft position sensor involves the use of a multimeter. Resistance can be checked across this sensor, and compared to resistance readings specified by the vehicle’s manufacturer.

Infinite resistance across the sensor’s terminals would indicate an “open” condition, while a lack of recordable resistance would indicate a “shorted” condition. Output of the crankshaft position sensor can also commonly be verified while cranking a vehicle’s engine, in the form of AC millivolts.

Alternatively, a quality OBD-II scan tool can also be used to validate crankshaft position sensor feedback. Live data reporting via a scan tool should show a rise/fall in pulse counts that parallel any rises or falls in engine RPM.

A lack of this feedback would require further diagnosis of the crankshaft position sensor and its corresponding circuit.

Can You Drive With a Bad Crankshaft Position Sensor?

Attempting to knowingly drive with a faulty crankshaft position sensor is never advised, due to a high risk of encountering driveability-related issues.

While it is true that some engines will continue to run despite a faulty crankshaft sensor, others will not, and even those that do, are not guaranteed to continue doing so indefinitely.

Modern computer-monitored engines rely upon accurate engine timing-related feedback to facilitate efficient and properly timed combustion. Without an uninterrupted stream of such data, a vehicle’s engine is likely to run erratically at best.

In some cases, an engine can even stall, and refuse to restart, if the signal from the crankshaft position sensor is lost.

With this in mind, issues pertaining to a vehicle’s crankshaft position sensor should always be diagnosed and repaired as soon as possible. Doing so can quite possibly prevent you from becoming stranded roadside, and will go a long way to eliminating any uncertainties.

If you lack the confidence or expertise to handle this repair on your own, it’s recommended to schedule an appointment with a reputable automotive service center as soon as possible.

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Josh Boyd

Josh has worked as a full-time mechanic for over 12 years, with 6 ASE (Automotive Service Excellence) certifications under his belt. He began his career as an automotive technician at local Toyota dealership and has since transitioned to specializing in diesel trucks and equipment.

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