P3400
Cylinder Deactivation System Bank 1
The engine control module has detected a fault in the cylinder deactivation system on bank 1. Variable displacement engines shut off cylinders under low load to save fuel — a fault here disables the function.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: hard
Common causes
Ordered by how often each turns out to be the cause.
- Deactivation solenoid or oil control valve failedCommon
- Collapsing lifter stuckPossible
- Low oil pressure prevents activationPossible
Parts involved
- Cylinder Deactivation Solenoid
- Lifter
- Oil Control Valve
P3400 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.