5 Symptoms of a Bad Crankshaft Position Sensor
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.
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.
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. 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.
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.
