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P0340Cars & SUVs
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P0340Camshaft position (CMP) sensor circuit

Content reviewed: Content reviewed by a heavy-duty technician. About our editorial approach

Check soon

— Missing cam signal can strand you with a no-start or sudden misfires. Do not ignore intermittent hot-no-start patterns—tow if it will not restart.

What does this severity mean?

General guidance only — not a substitute for a professional inspection or official roadside / out-of-service criteria (e.g. CVSA OOSC) in your jurisdiction.

Part of system: Electrical sensing & powertrain inputs · Wire gauge & ampacity tool

With P0340, prove the circuit before you condemn the part named in the scanner text. P0340 means the camshaft position sensor signal is missing or implausible, so the ECM cannot sync injection and spark to cam timing. Results range from extended cranking and misfires to a no-start. Scope the cam sensor for a clean square wave while cranking, verify power/ground/reference, and check the reluctor or tone wheel for damage before replacing the sensor. Timing chain stretch that shifts cam correlation can set this alongside crank/cam correlation codes. Discriminate among failed camshaft position sensor, open, shorted, or oil-contaminated sensor wiring, and damaged cam reluctor or tone wheel using voltage drop and connector integrity. Verify by scope cam and crank signals together while cranking, then verify sensor supply, ground, and signal at the connector; replace camshaft position sensor only when the wiring path checks out clean.

Parts that may be involved

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Vehicles often affected

Engines with oil-soaked cam connectors after valve-cover leaks, or stretched timing chains shifting correlation.

Typical symptoms

  • Extended cranking or intermittent no-start when hot
  • Cam sensor PID flatlines while crank sensor still pulses
  • Misfires immediately after start until the signal returns
  • Cam/crank correlation codes stored with P0340
  • Oil-soaked connector at the cam sensor after a valve-cover leak

Likely causes

  • Failed camshaft position sensor
  • Open, shorted, or oil-contaminated sensor wiring
  • Damaged cam reluctor or tone wheel
  • Incorrect cam timing from chain/belt jump or stretch
  • Lost 5 V reference shared with other sensors

Recommended checks

  1. 1

    Scope cam and crank signals together while cranking

  2. 2

    Verify sensor supply, ground, and signal at the connector

  3. 3

    Inspect the tone wheel through the sensor bore if accessible

  4. 4

    Check cam/crank correlation PIDs before major timing teardown

  5. 5

    Replace the sensor and reseal oil leaks that contaminate the connector

DIY vs professional

DIY-safe: connector clean/reseal and sensor swap if accessible. Pro: scoping cam/crank together and timing teardown are shop jobs.

See also

Related terms

Content reviewed by a heavy-duty technician. About our editorial approach