CKPSensor

Crankshaft Position Sensor (CKP)

Group: Engine position and speed

The CKP sensor tells the computer the position and rotating speed of the crankshaft. Without its signal there is no spark and no injection, so a failed CKP usually leaves the engine cranking without starting or makes it stall while driving.

Contents

What does the CKP sensor do?

It reads the teeth of a reluctor (tone) wheel mounted on the crankshaft or the flywheel. A gap of one or two missing teeth acts as a reference to locate top dead center of cylinder 1. With that information the computer calculates engine speed (RPM), decides the exact moment for ignition and injection, and detects misfires by measuring small speed changes between each combustion event. That is why many manuals also call it the TDC sensor or the RPM sensor: it is the same part.

Where is it located?

Near the crankshaft pulley, on the block next to the flywheel (sometimes reached from underneath, behind the transmission) or in the timing cover. It usually has a 2 or 3-wire connector.

Signal type and reference values

  • Inductive (2 wires): generates its own AC voltage. Typical resistance is 200 to 1,200 ohms; while cranking it produces from 0.5 V to several volts AC.
  • Hall effect or magnetoresistive (3 wires): 5 V or 12 V supply, ground and a square-wave signal switching between 0 and 5 V.
  • Typical air gap (distance to the tone wheel): 0.5 to 1.5 mm.

Values are a guide only: always check the manufacturer's data for your engine.

Symptoms of a bad CKP sensor

  • The engine cranks but does not start: no spark and no injector pulse.
  • The engine stalls when hot and restarts once it cools down (a classic thermal failure of the CKP).
  • Bucking, misfires or cutting out at high RPM.
  • The tachometer drops to zero or jumps while driving.
  • Check engine light with codes P0335 to P0339.

How to test the CKP sensor step by step

  1. Watch the live data while cranking: if RPM reads 0, the computer is not receiving the CKP signal.
  2. Inspect the connector and wiring: oil inside the connector, green pins or chafed wires near the exhaust.
  3. 2-wire sensor: measure the resistance between its terminals and compare it with the manual (as a guide, 200 to 1,200 ohms). Infinite or 0 ohms means the sensor is bad.
  4. 3-wire sensor: with the ignition on, check for 5 V or 12 V on the supply and less than 0.1 V drop on the ground.
  5. With the multimeter on AC volts (inductive) or with an oscilloscope (Hall), crank the engine and confirm that a signal appears.
  6. Check the sensor tip: metal shavings stuck to it or a damaged tone wheel distort the signal.
  7. After replacing it, some vehicles (GM, Ford) need the CKP variation relearn with a scan tool.

Trouble codes related to the CKP sensor

Frequently asked questions about the CKP sensor

Are the CKP sensor and the RPM sensor the same thing?
Yes. On almost every modern engine the crankshaft position sensor is the one that reports engine speed. It is also called the TDC sensor because it marks top dead center.
Can I drive with a bad CKP sensor?
It is not recommended: it can shut the engine off while you are driving and leave you without power steering or brake assist. If the engine stalls when hot, have it checked as soon as possible.

Updated September 25, 2026. Values are a guide only: always confirm them in the service manual for your engine.

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