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P0340 — Camshaft Position Sensor Circuit Fault

P0340 is set when the engine control module cannot interpret the camshaft position sensor signal on the primary cam (or the single cam on engines with one sensor). The signal might be missing entirely, out of phase with the crankshaft signal, or showing electrical noise. Because the ECM uses cam position to time fuel injection and ignition, a P0340 will typically cause a hard start, a no-start, or a stall.

P0340 means camshaft position sensor circuit fault. A vehicle usually stays drivable short-term with this code, but it should be diagnosed promptly. The most common cause is failed camshaft position sensor (most common after 100k miles) (typically $100–$400). Causes and cost vary by make and model; confirm the root cause before replacing parts.

Severity: high powertrain Safe to drive (short term)

Reviewed by MECH AI Editorial · Last verified

What does P0340 mean?

P0340 is set when the engine control module cannot interpret the camshaft position sensor signal on the primary cam (or the single cam on engines with one sensor). The signal might be missing entirely, out of phase with the crankshaft signal, or showing electrical noise. Because the ECM uses cam position to time fuel injection and ignition, a P0340 will typically cause a hard start, a no-start, or a stall.

What are the symptoms of P0340?

What causes P0340?

Cause Likelihood Estimated repair (USD)
Failed camshaft position sensor (most common after 100k miles) Most common $100–$400
Damaged or corroded sensor connector Common $50–$250
Chafed or broken sensor wiring Common $80–$350
Loose, slipped, or worn camshaft sensor reluctor wheel Occasional $300–$1,200
Timing chain stretch causing cam-crank correlation drift Occasional $800–$3,000
Failed PCM driver for the cam sensor input (rare) Rare $400–$1,500

Repair costs are typical US ranges and vary by make, model, model year, and labor rate. A diagnostic trouble code is a symptom, not a guaranteed failed part — confirm the root cause before replacing anything.

Is it safe to drive with P0340?

In most cases a vehicle stays drivable for short trips with P0340 active, but you should diagnose and repair it promptly. This is a high-severity code — ignoring it can lead to further damage or a failed emissions test. Exact tolerance depends on your specific make and model.

How to diagnose P0340

  1. Inspect the connector and wiring at the cam sensor

    Locate the cam sensor (usually near the front of the cylinder head, threaded into the head or timing cover). Disconnect the sensor and inspect the connector for corrosion, bent pins, or water intrusion. Inspect the harness for chafing against engine mounts or accessory brackets.

    Tools: Connector unlock tool, Flashlight, Electrical contact cleaner

  2. Test the sensor signal with a scope or scan tool

    With the engine cranking or running, the cam sensor should produce a square-wave or sine-wave signal that the scan tool can graph. No signal or a noisy signal indicates the sensor or its wiring is bad. A clean signal that the ECM does not respond to suggests an ECM input fault.

    Tools: Scan tool with cam sensor PID, or oscilloscope, Multimeter

  3. Verify cam-crank correlation in live data

    Watch the cam and crank position signals together while cranking. They should maintain a fixed timing relationship. If the cam signal drifts relative to the crank signal over time, suspect timing chain stretch or a slipped reluctor wheel.

    Tools: Scan tool with dual-PID graphing

  4. Check sensor power and ground at the connector

    With the connector unplugged and the key on, verify battery voltage on the power wire and continuity from the ground wire to a known good chassis ground. Missing power or poor ground will produce P0340 with a perfectly good sensor.

    Tools: Multimeter, Wiring diagram

  5. Inspect the reluctor / target wheel on the camshaft

    If the wiring tests good and the sensor is new but P0340 persists, remove the sensor and shine a light at the reluctor wheel through the sensor port. Damaged or oil-fouled teeth will not generate a clean signal. On some engines the reluctor is a separate pressed-on piece that can slip.

    Tools: Inspection mirror, Bright flashlight

How do I fix P0340?

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P0340: frequently asked questions

What does diagnostic trouble code P0340 mean?

P0340 is set when the engine control module cannot interpret the camshaft position sensor signal on the primary cam (or the single cam on engines with one sensor). The signal might be missing entirely, out of phase with the crankshaft signal, or showing electrical noise. Because the ECM uses cam position to time fuel injection and ignition, a P0340 will typically cause a hard start, a no-start, or a stall.

What are the symptoms of P0340?

Check Engine Light is illuminated. Hard cranking or extended crank time before the engine starts. Intermittent stalling, especially when the engine is hot. Engine cuts out and restarts after a short delay. Possible complete no-start condition. Rough running and reduced power if the engine does run

What causes P0340?

Failed camshaft position sensor (most common after 100k miles) (most-common). Damaged or corroded sensor connector (common). Chafed or broken sensor wiring (common). Loose, slipped, or worn camshaft sensor reluctor wheel (occasional). Timing chain stretch causing cam-crank correlation drift (occasional). Failed PCM driver for the cam sensor input (rare) (rare)

Is it safe to drive with P0340?

In most cases a vehicle stays drivable for short trips with P0340 active, but it should be diagnosed and repaired promptly — this is a high-severity code. Ignoring it can lead to further damage or a failed emissions test. Specific tolerance varies by make and model.