Powertrain, shared range

P3430 Cylinder 4 Exhaust Valve Control Performance

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

P3430 would cover exhaust valves on cylinder 4 that keep opening, or stay shut, against the command while the circuit itself is sound. No manufacturer documents this code publicly. Ford shows both sides of the problem: a Ford patent recognises an exhaust valve opening after shutdown from changes in exhaust pressure and responds by reactivating the cylinder and storing a code, while in practice the 2025 F-150 5.0 l reports a cylinder 4 switching fault as P3426 and traces it to a restricted solenoid oil feed tube (bulletin 26-2093). An exhaust valve that does not stay closed lets fresh air reach the catalyst and the oxygen sensors, which can show up as fuel trim errors, misfire counts and vibration.

Likely causes

Restricted oil supply to the cylinder 4 switching elements

Exhaust lifter or rocker of cylinder 4 not changing state

Oil too thin, too old or too low

Symptoms

Vibration in reduced-cylinder mode
Lean or rich fuel trim codes
Check engine lamp on

Repair estimate

DifficultyHardWorkshop job

Parts and labour€100–3,500

Time0–12 h

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

Parts involved

cylinder deactivation solenoidlifterengine oil

References: law.cornell.edu, patents.google.com, static.nhtsa.gov.