P3498Cylinder 1 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
- P3498 flags a mechanical failure on cylinder 1: the control unit commanded it off, but its valves kept opening. This differs from P3402, which concerns the control side, and from the wiring codes P3401, P3403 and P3404. GM runs the check on its 5.3 l L84 and 6.2 l L87 Dynamic Fuel Management V8s by watching filtered manifold pressure every 90 crank degrees; if it stays above a threshold while cylinder 1 should be resting, 22 failures in 25 chances log a Type B code. Mazda's 2.5 l engines, which deactivate cylinders 1 and 4, show it together with P349B when a rocker arm has dropped out or broken (SA-041/18, SA-022/19); Mazda then authorises a replacement engine. Drivers notice the lamp, rough running or a loss of power.
- What you may notice
- Check engine lamp on
- Rough idle or misfire on cylinder 1 (P0301)
- Clatter from the cylinder head and loss of power
- Cylinder deactivation no longer used, higher fuel use
- Likely causes
- LikelySwitchable rocker arm of cylinder 1 dropped out or broken (Mazda)
- PossibleDeactivation lifter of cylinder 1 stays locked (GM DFM)
- PossibleLifter oil solenoid of cylinder 1 sticking or with protruding pole piece
- PossibleOverdue oil changes or wrong oil grade
- 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: €100 – €6,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.