Powertrain, shared range

P3418 Cylinder 3 Deactivation/Intake Valve Control Performance

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

P3418 is meant for a cylinder 3 deactivation that is wired correctly yet does not respond as requested: the cylinder keeps breathing when it should rest, or fails to come back. No manufacturer documents this code publicly. GM tests the hardware of cylinder 3 under its own code P349A; bulletin 20-NA-204 for the 2021 L84 and L87 notes that a voltage dip during cranking can briefly disable the outputs and set that code without a real fault. Honda shows the same failure pattern in another form: in bulletin 13-055 excess cold-start oil pressure pushed cylinders 1 to 4 into cut mode uncommanded, logged as P3400/P3497 with misfires. Circuit faults belong to P3417, P3419 and P3420. Expect rough running and a misfire code.

Likely causes

Low oil level, wrong viscosity or aged oil

Lifter or rocker of cylinder 3 not locking or unlocking

Cylinder 3 control valve sticking or its screen blocked

Oil pressure too high or too low for the switching window

Symptoms

Misfire code for cylinder 3 (P0303)
Shudder when the engine changes between modes
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, static.nhtsa.gov, static.nhtsa.gov.