P0340 — Camshaft Position (CMP) Sensor Circuit

Causes

• Failed camshaft position (CMP) sensor
• Open, shorted, or damaged CMP sensor wiring harness
• Corroded or loose connector at sensor or ECM/PCM
• No reference voltage or ground to CMP sensor
• Timing chain/belt jumped, worn cam reluctor/target, or phaser failure
• Oil contamination or debris on sensor/reluctor

Symptoms

• Check Engine Light (MIL) illuminated
• No-start or hard-start condition
• Rough idle, stalling, or intermittent misfire
• Poor acceleration or reduced engine power
• Poor fuel economy
• Diagnostic trouble codes related to cam/crank correlation (misfire codes, crank sensor codes)

What to check

• Verify DTC P0340 and related codes using a scan tool; record freeze frame/live data
• Perform a visual inspection of CMP sensor, connector, and wiring for damage, corrosion, oil, or loose pins
• Backprobe sensor connector and verify reference voltage (typically 5V or 12V depending on design) and ground with ignition ON
• Check CMP signal with an oscilloscope while cranking/running; look for a clean square wave (Hall) or AC sine/pulse (VR)
• Check continuity and resistance between sensor signal/ground and PCM connector; check for shorts to battery or ground
• Inspect camshaft reluctor/target and timing components for damage, play, or timing jump

Signal parameters

• Hall-effect CMP: digital square wave, 0–5 V logic-level pulses, duty ~40–60%, frequency varies with engine speed
• Variable-reluctance (VR) CMP: AC sine pulses, amplitude ~0.1–1.5 VAC at low speed up to several volts at higher RPM
• Reference supply: commonly 5 V (some designs use switched 12 V) to the sensor; ground must be solid
• Typical signal frequency corresponds to camshaft RPM (half crank RPM for 4-stroke engines); expect clean, regular pulses when cranking/running
• Low/no signal, random pulses, or stuck-high/stuck-low indicate sensor, wiring, or timing issues

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