P0340 on a GMC: Causes, Fixes & Repair Cost

⚠️ Severe · not recommended to drive

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

What P0340 means on a GMC

On a GMC, 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 GMCs?

P0340 shows up on GMC trucks and SUVs with higher mileage, especially the Sierra with the 5.3L V8 and the Terrain and Acadia with four-cylinder and V6 engines. The camshaft position sensor sits near the front timing area, and sensor failure is the usual cause. Wiring problems at the connector are also common on these engines.

Commonly reported on: Sierra, Terrain, Acadia, Canyon.

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 timing issues

How to fix it

Fix	DIY?	Typical cost
Replace the camshaft position sensor	Yes	$40–130
Repair damaged sensor wiring or connector	Mechanic	$100–250
Have a mechanic check the timing chain and guides	Mechanic	$900–1600