Draft guidance: awaiting Claude spot-check, qualified-mechanic review and named-editor approval. Do not use a fault code alone to replace parts.

P0340: Camshaft position sensor A circuit malfunction

The control module has detected a missing or invalid signal in camshaft-position sensor A’s circuit, generally for Bank 1 or a single-sensor layout.

What P0340 means

The control module has detected a missing or invalid signal in camshaft-position sensor A’s circuit, generally for Bank 1 or a single-sensor layout. “Circuit” includes the sensor, connector, wiring, supply, earth and module input, so fitting a sensor without testing may not cure it.

Can I still drive?

Arrange diagnosis promptly because the vehicle may stall or fail to restart, and some causes involve mechanical valve timing. Recover it if starting is difficult, it stalls, misfires badly, loses substantial power or makes abnormal timing-chain or belt noise. If it runs normally with only a steady light, limit use to a short direct journey to a repairer; recovery is the lower-risk option.

Symptoms

  • Hard starting, extended cranking or no-start.
  • Stalling, rough running or misfire.
  • Hesitation and reduced acceleration.
  • Poorer fuel economy.
  • Limp-mode or transmission behaviour on some vehicles.

Common causes

  • Failed camshaft-position sensor.
  • Open, shorted, grounded or heat-damaged wiring.
  • Loose, oily or corroded connector.
  • Missing power supply or earth.
  • Damaged camshaft trigger wheel.
  • Crank-sensor, shared-circuit or mechanical timing fault.
  • Rare control-module fault.

Safe first checks

  • Retain all codes and freeze-frame data, especially crank/cam correlation codes. With the engine cold and switched off, check the sensor connector and visible loom for loose pins, oil ingress, corrosion, chafing and signs of recent repair work. Check battery terminals and general cranking behaviour. Do not continue running an engine with timing noise, and do not remove timing covers or probe live circuits without model-specific information.

Typical UK fix cost

Expect £90–£180 for diagnosis and around £170–£500 total for a normal sensor or harness repair; difficult access may lift this to £600–£850. A confirmed timing belt, chain, actuator or trigger-wheel problem may cost £650–£2,000+.

Related models

This is a generic OBD-II code used across many makes and models. The exact test thresholds, component layout and repair route vary by engine and manufacturer, so check vehicle-specific technical information before ordering parts.

Related fault codes

Sources

A diagnostic trouble code identifies a system or circuit to investigate. It does not prove that a named part has failed. Preserve freeze-frame data and seek a vehicle-specific diagnosis before clearing the code.