Powertrain, shared range

P3426 Cylinder 4 Deactivation/Intake Valve Control Performance

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

P3426 is one of the few performance codes in this range that makers really use. FCA calls it Cylinder 4 Deactivation Control Performance on the 6.4 l Heavy Duty Hemi with MDS; bulletins 18-082-16 and 18-036-20 list it with P3402, P3442 and P3450 and fix it with new PCM software. Ford stores it on the 2025 F-150 5.0 l: bulletin 25-2487, replaced by 26-2093, traces P3402 and P3426 to a restricted oil feed tube for the right-bank deactivation solenoids, which is replaced under the valve cover. GM checks cylinder 4 mechanically under P349B instead. Circuit faults are P3425, P3427 and P3428. The lamp comes on, and the engine may run rough or stay in full-cylinder mode.

Likely causes

Restricted oil feed tube to the deactivation solenoids (Ford 5.0 l, TSB 26-2093)

Control software needing an update (FCA 6.4 l Hemi)

Low or worn-out engine oil

Deactivating lifter of cylinder 4 sticking

Symptoms

Check engine lamp on
Misfire on cylinder 4 or rough running
Drone or shudder at light throttle

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, static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov.