Engine

P0343 — Camshaft Position Sensor A Circuit High Input (Bank 1)

Severity: medium Drive with care, to a shop

What P0343 means

The engine control module uses the camshaft position sensor to know which stroke each cylinder is on, so it can time fuel injection and spark correctly. P0343 sets when the Bank 1 sensor A circuit reads higher than expected or gives an implausible signal. The cause may be the sensor, a wiring open or short to voltage, or a fault in the module's input.

Symptoms

  • Check Engine Light on
  • Rough idle or misfires
  • Hard starting or no-start
  • Loss of power or hesitation
  • Engine stalling
  • Worse fuel economy

Possible causes

  1. Failed camshaft position sensor
  2. Damaged wiring harness or connector (open, short, corrosion)
  3. Broken or chafed wire near the valve cover
  4. Signal wire shorted to voltage
  5. Poor connection at the sensor connector or ground
  6. Jumped or stretched timing belt or chain
  7. Fault in the PCM input circuit

How to diagnose

  1. Scan for codes and freeze frame data, and note any crankshaft or other camshaft sensor codes
  2. Inspect the sensor, connector and harness near the valve cover for oil, cracks, corrosion and chafing
  3. Check that the connector is seated and its terminals are tight and clean
  4. Use a multimeter to test sensor power, ground and signal wire for opens and shorts to voltage
  5. View the sensor signal with a scope or live data while cranking
  6. Compare the camshaft signal with the crankshaft signal for correlation
  7. Verify cam timing and the condition of the belt or chain
  8. If wiring and power are good, test the PCM before replacing it

Common fixes

  • Replace the camshaft position sensor
  • Repair or replace damaged wiring and connectors
  • Clean terminals and restore a good ground
  • Correct the cam timing or replace a stretched chain or belt
  • Repair or replace the PCM if confirmed faulty

Questions and answers

Can I drive with a P0343 code?

Only for a short trip to a shop. The engine can stall or fail to restart, so don't put it off.

What most often causes P0343?

Usually the camshaft sensor itself or damaged wiring and connectors near it. Inspect the harness and terminals first, then replace the sensor if they are fine.

Will clearing the code fix it?

Clearing only turns off the light. If the cause remains, the code returns, so fix the sensor or wiring, then clear it and confirm it stays off.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.