Distributorless ignition systems require (CKP)-(CMP) – Crankshaft-Camshaft Position Sensors.

These (CKP)-(CMP) Sensors serve essentially the same purpose as the ignition pickup and trigger wheel in an electronic distributor.

The big difference being that the basic timing signal is read off the crankshaft instead of the distributor shaft.

This eliminates ignition timing variations that can result from wear and backlash in the timing chain and distributor gear.

As a result, This also eliminates any need for timing adjustments.

Crankshaft-Camshaft Position Sensors
Crankshaft-Camshaft Position Sensors

The ECM uses signal pulses from the crank position sensor (CKP) to calculate when a particular cylinder is approaching top dead center. The pulses from the cam position sensor (CMP) are used to decide whether it is on a compression or an exhaust stroke.

When either signal is lost, the ECM may shut down ignition, injection or both. Sensor failures are extremely common on certain makes. In the past, a failed sensor frequently meant a no-start or an engine that died “just like you turned off the key” going down the road.

What does a Camshaft/Crankshaft Position Sensor do?

  • The Camshaft sensor determines which cylinder is firing to establish injector synchronization and coil firing sequence in DIS systems. Crankshaft sensors set ignition timing, supply the RPM signal, and determine engine speed.

Where are these sensors located?

  • The Camshaft Position sensor is typically located in the cylinder head of the engine and has a cylindrical portion that inserts into the head. The Crankshaft Position sensor is normally located in the timing cover or on the side of the block with a cylindrical portion that inserts into the block.

Will a malfunctioning Cam or Crank Sensor illuminate the check engine light or affect vehicle operation?

  • Yes, a failing sensor can illuminate the MIL, and may cause vehicle stalling or a no-start condition.

What are the common causes of failure?

  • Typically these sensors fail due to exposure to high heat.

How to determine if these sensors are malfunctioning?

  • Look for RPM on a scan tool while cranking the engine. If the engine runs, a scope is the best diagnostic tool. Typical trouble codes: Crankshaft P0335; Camshaft P0340.

(CMP) – Camshaft Position Sensors

The camshaft sensor monitors the frequency at which the camshaft is turning. The camshaft sensor records the rate at which the camshaft is rotating. By extension, this tells the computer the rate at which the engine’s valves are opening and closing.

(CKP) – Crankshaft Position Sensors

As the gas and air that the valves have pumped into the ignition chambers combust, the force against the piston causes the crankshaft to turn. The crankshaft sensor keeps track of the rate at which the crankshaft is rotating.

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(CKP)-(CMP) – Crankshaft-Camshaft Position Sensors Engine Codes

The fastest way to check the crank and/or camshaft sensors on a 1995 or newer vehicle with OBD II is to plug in your scan tool and check for any fault codes.

You can also use your scan tool to check for the presence of a cranking rpm signal if an engine is cranking but is not starting because there is no spark (which is often a clue that the crankshaft position sensor is not working).