Powertrain, shared range

P3400 Cylinder Deactivation System Bank 1

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

P3400 is the bank-level verdict: the engine computer has concluded that cylinder deactivation on bank 1 as a whole does not behave as commanded, without blaming a single circuit. Makers fill it differently. On the 2019 LT4 Corvette, GM compares a manifold pressure model with all cylinders firing against the same model while cylinders are off; 100 failed samples out of 200 give a Type B code. Mazda's 2.5 l four-cylinders store it when a deactivation oil control valve is clogged, for example by plastic from the filter wrapper (SA-061/20). In Honda's VCM V6 it stems from a rocker arm oil pressure switch, and the Hemi Ram 1500 got a PCM update for it. Bank 2 is P3497. The lamp comes on; misfires or rough running may follow.

Likely causes

Deactivation oil control valve or its screen clogged by debris

Low oil level, wrong grade or overdue oil change

Switchable rocker arm or lifter broken, dislodged or not latching

Oil pressure too high on cold start, e.g. weak relief valve spring

Engine control software needing an update

Symptoms

Check engine lamp on
Rough idle or misfire codes on the deactivating cylinders
Ticking or clattering from the valve train
Reduced-cylinder mode no longer used, higher fuel use

Repair estimate

DifficultyHardWorkshop job

Parts and labour€80–4,000

Time0–12 h

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

Parts involved

cylinder deactivation solenoidlifteroil control valve

References: law.cornell.edu, gsi.ext.gm.com, static.nhtsa.gov, static.nhtsa.gov.