P0340 — Camshaft position (CMP) sensor circuit

Part of system: Electrical sensing & powertrain inputs

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.