P349ACylinder 3 Deactivation/Intake Valve Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- P349A states that cylinder 3 kept its valves working while the engine computer had switched it off. GM picks this up on its L84 and L87 V8s through manifold pressure that stays too high during the skipped strokes, Type B after 22 failed checks out of 25. Not every stored P349A means a worn lifter. For the 2021 Tahoe, Suburban, Yukon and Escalade, GM explains (PIP5731, later bulletin 20-NA-204) that a voltage dip while cranking could make the ECM drop the deactivation outputs for one trip and log this code in history without a real defect; the cure is new ECM software and a road test with a warm engine at 30 to 45 mph. If it returns, the lifters and the solenoid of cylinder 3 need checking. P3418 covers the control side.
- What you may notice
- Code stored in history with no noticeable concern
- Check engine lamp on if the fault is real
- Ticking noise or higher fuel use
- Likely causes
- PossibleVoltage dip at cranking disabled the outputs, ECM software outdated
- PossibleDeactivation lifter of cylinder 3 does not unlock
- PossibleLifter oil solenoid of cylinder 3 sticking
- RareLow or aged oil slowing the switching
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €0 – €4,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.