P0340 GMC Sierra 1500
Camshaft Position Sensor Circuit Malfunction (Bank 1) · Powertrain Code · High · Repair: Moderate
What is P0340?
The camshaft position sensor on bank 1 is not providing a valid signal. Engine may not start or run poorly.
When the GMC Sierra 1500 triggers code P0340 (camshaft position sensor circuit malfunction (bank 1)), it typically points to an issue in the powertrain system. This is a high severity code, so address it promptly to avoid further damage or safety concerns. Below you'll find the most common causes, symptoms, and repair options specific to the GMC Sierra 1500.
This repair is rated moderate, meaning some experience and specialty tools required.
Diagnostic data on this page is compiled from publicly available repair resources and technical service bulletins. Always have a qualified mechanic confirm the diagnosis before authorizing repairs on your GMC Sierra 1500.
Common Causes on GMC Sierra 1500
- Failed camshaft position sensor (CMP)
- Damaged or stretched timing chain causing signal irregularity (common on 1.5T L3B/LYX)
- CMP sensor wiring damage or connector fault
- Oil contamination on the CMP sensor tip
Symptoms
- Check Engine Light on
- Hard starting or intermittent no-start
- Engine may stall
- Rough running and misfires
- Reduced engine power
Notes for GMC Sierra 1500
On GM 1.5T engines, a P0340 combined with rattle on cold start often indicates timing chain stretch — do not ignore this as chain failure can cause catastrophic engine damage.