Powertrain, shared range

P3498 Cylinder 1 Deactivation/Intake Valve Performance

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

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.

Likely causes

Switchable rocker arm of cylinder 1 dropped out or broken (Mazda)

Deactivation lifter of cylinder 1 stays locked (GM DFM)

Lifter oil solenoid of cylinder 1 sticking or with protruding pole piece

Overdue oil changes or wrong oil grade

Symptoms

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

Repair estimate

DifficultyHardWorkshop job

Parts and labour€100–6,000

Time0–16 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

liftervalve traincylinder deactivation solenoidengine oil

References: gsi.ext.gm.com, static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov.