P0340 on a Mazda: Causes, Fixes & Repair Cost

⚠️ Severe · not recommended to drive

The engine may not start, or it may stall while driving, so have the car towed if it won't start.

What P0340 means on a Mazda

On a Mazda, P0340 means the engine computer is getting no signal or a bad signal from the camshaft position sensor. Without camshaft position, the computer can't time fuel injection correctly, and the engine may refuse to start or may stall.

Is P0340 common on Mazdas?

P0340 shows up on Mazdas with higher mileage, often Mazda3, Mazda6, CX-5, and MX-5 models with Skyactiv engines. The camshaft position sensor fails with age and mileage, and wiring problems at the sensor connector are another common cause on these engines.

Commonly reported on: Mazda3, Mazda6, CX-5, MX-5.

Symptoms

Check engine light is on
Engine cranks but won't start
Engine stalls while driving
Rough running or loss of power

Common causes

most common: Failed camshaft position sensor
common: Damaged wiring or connector at the sensor
common: Oil or debris on the sensor face
less common: Timing chain or VVT timing issues

How to fix it

Fix	DIY?	Typical cost
Replace the camshaft position sensor	Yes	$40–140
Repair damaged sensor wiring or connector	Mechanic	$100–250
Have a mechanic check the timing chain and VVT components	Mechanic	$800–1500