Powertrain, shared range

P34A0 Cylinder 9 Deactivation/Intake Valve Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P34A0 is reserved for a cylinder 9 that keeps its valves moving after the engine computer has ordered it off, which presumes an engine with at least nine cylinders and per-cylinder valve switching. No manufacturer documents this code publicly. The twelve-cylinder engines with deactivation found so far work bank by bank; Bentley's W12 in the 2020 Bentayga Speed, for example, alternates between two complete banks of six. A monitor would work like GM's tests for cylinders 1 to 8 (P3498 to P349F), where manifold pressure that stays too high in skipped events reveals a cylinder that is still breathing. CARB requires such mechanical checks for valve control systems. P3466 is the control-performance code for cylinder 9.

Likely causes

Switching lifter or rocker of cylinder 9 stuck
Oil control valve for the deactivation not switching
Low or degraded oil

Symptoms

  • Check engine lamp on
  • Rough running in reduced-cylinder mode
  • Higher fuel use

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€150–6,000
Time1–16 h

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

Parts involved

liftervalve traincylinder deactivation solenoidengine oil

Related codes

P3466P3465P349FP34A1P0309

References: law.cornell.edu, gsi.ext.gm.com, bentleymedia.com.