OBD-II code · Powertrain (manufacturer / generic)
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.
Is it safe to drive with P3400?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelyDeactivation solenoid or oil control valve failed
- PossibleCollapsing lifter stuck
- PossibleLow oil pressure prevents activation
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1.5–8 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Cylinder Deactivation Solenoid, Lifter, Oil Control Valve
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.