The crankshaft position sensor is one of the most important sensors in your engine. It watches the crankshaft spin and tells the engine computer exactly where the pistons are and how fast the engine is turning. Without this signal, the computer cannot fire the spark plugs or inject fuel at the right moment, which is why a failed crank sensor usually means a no-start.
Animated: how a Crankshaft Position Sensor actually works
🔧 How It Works, Step by Step
1
Read the reluctor wheel
A toothed wheel called a reluctor or tone ring is bolted to the crankshaft and spins with it. The sensor sits just a hair away from the passing teeth.
2
Generate a pulse
As each tooth passes the sensor tip, it disturbs a magnetic field. A magnetic sensor makes its own voltage pulse, while a Hall-effect sensor switches a supplied voltage on and off.
3
Mark the missing tooth
The reluctor wheel has one or two teeth missing to create a gap. That gap acts as a reference point so the computer knows exactly which position the crankshaft is in.
4
Send position and speed
The stream of pulses tells the engine computer both crank angle and RPM. The computer uses this to time spark and fuel delivery precisely.
🧩 The Key Parts
Sensor tip
Contains the magnet or Hall element that detects the passing reluctor teeth.
Reluctor wheel
Toothed ring on the crankshaft with a missing tooth that provides the reference gap.
Signal wiring
Carries the pulse signal, power, and ground between the sensor and the engine computer.
Air gap
The small clearance between the sensor and reluctor teeth that must stay consistent for a clean signal.
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The 50 most common check engine codes with likely cause and DIY fix cost. Sent once.
🩺 Signs of a Failing Crankshaft Position Sensor
Engine cranks but will not start
Intermittent stalling, especially when hot
Check engine light on
Erratic or jumping tachometer
Hard starting or long crank times
Random misfires under load
⚠️ Common Problems
Heat-related failure
The sensor electronics can break down when the engine gets hot, causing a stall that clears once the engine cools.
Debris or damaged teeth
Metal shavings on a magnetic sensor or chipped reluctor teeth distort the signal and confuse the computer.
Wiring and connector faults
Corroded pins, broken wires, or a loose connector interrupt the signal and can mimic a bad sensor.
💰 Cost to Fix
$120-$350typical range to repair or replace, parts and labor
❓ FAQ
Can I drive with a bad crankshaft position sensor?
Not reliably. Once it fails the engine may stall without warning or refuse to start, so it should be replaced promptly.
What is the difference between the crank and cam sensor?
The crank sensor tracks the crankshaft for RPM and base timing, while the cam sensor tracks the camshaft to identify the exact cylinder on its firing stroke.
Does a bad crank sensor throw a code?
Usually yes. Common codes are P0335 and P0336, though the engine can still fail before a code sets.