Camshaft Position Sensor (CMP)

What does the CMP sensor do?

The crankshaft turns twice for every complete engine cycle, so the CKP alone cannot tell whether cylinder 1 is on its compression or exhaust stroke. The CMP reads a notch or wheel on the camshaft and resolves that question. On engines with variable valve timing (VVT, VANOS, VTC) the computer also compares the CMP signal with the CKP signal to know how far the camshaft has been advanced or retarded.

Where is it located?

On the cylinder head, usually at the front or rear of the valve cover, next to the end of the camshaft. Dual overhead cam engines with variable timing have one per camshaft (intake and exhaust) and sometimes one per bank.

Signal type and reference values

• Almost always Hall effect: 3 wires (5 V or 12 V supply, ground and a 0 to 5 V square-wave signal).
• Some older engines use 2-wire inductive sensors.
• CKP/CMP correlation must be within a few degrees; a bigger deviation sets P0016 to P0019.

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

Symptoms of a bad CMP sensor

• Long cranking: the engine takes several seconds to start while the computer looks for synchronization.
• Loss of power or bucking caused by out-of-phase injection.
• Higher fuel consumption.
• On some models, the engine stalls or does not start.
• Check engine light with P0340 or correlation codes.

How to test the CMP sensor step by step

1. Read the codes: P0340 points to the circuit; P0016 or P0017 mean the signal arrives but does not match the crankshaft (possibly a stretched chain).
2. Check the connector: CMP sensors close to the valve cover often have oil seeping inside.
3. With the ignition on, check the supply (5 V or 12 V) and ground at the connector.
4. With the engine turning, measure the signal: it should switch between 0 and 5 V (on an oscilloscope you will see a clean pulse train).
5. If the circuit is good and there is a correlation code, verify the timing before replacing sensors.

Trouble codes related to the CMP sensor

• P0010A Camshaft Position Actuator Circuit (Bank 1)Severity Medium
• P0011A Camshaft Position Timing Over-Advanced or System Performance (Bank 1)Severity Medium
• P0014B Camshaft Position Timing Over-Advanced or System Performance (Bank 1)Severity Medium
• P0016Crankshaft Position Camshaft Position Correlation (Bank 1 Sensor A)Severity High
• P0017Crankshaft Position Camshaft Position Correlation (Bank 1 Sensor B)Severity High
• P0340Camshaft Position Sensor A Circuit Malfunction (Bank 1 or Single Sensor)Severity High
• P0341Camshaft Position Sensor A Circuit Range/Performance (Bank 1)Severity High
• P0342Camshaft Position Sensor A Circuit Low (Bank 1)Severity High
• P0343Camshaft Position Sensor A Circuit High (Bank 1)Severity Medium
• P0344Camshaft Position Sensor A Circuit Intermittent (Bank 1)Severity High
• P0345Camshaft Position Sensor A Circuit (Bank 2)Severity High

Frequently asked questions about the CMP sensor