What does it mean?
P3412 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Cylinder 2 Deactivation/Intake Valve Control Circuit High . This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms
- MIL (check engine lamp) is on and the code stores with freeze frame data
- Cylinder deactivation / variable lift is disabled, so the engine stays in full-cylinder mode and fuel consumption climbs
- Rough idle and a noticeable shake if the valve is left in the collapsed position
- Tapping or ticking from the cylinder head above cylinder 2
- Misfire on cylinder 2, often with additional misfire codes stored alongside
- Slightly reduced power and a flat, unresponsive feel under light throttle
Likely causes
- Control wire shorted to battery voltage or touching another live feed inside the engine harness
- Open or high-resistance ground return for the solenoid, which leaves the driver circuit sitting high
- Open winding inside the cylinder 2 deactivation solenoid, so the module never sees current being drawn
- Oil-soaked, corroded or spread terminals at the valve lifter oil manifold connector; engine oil wicking up this harness is a known weak point
- Harness chafed against the cylinder head, the valve cover rail or a mounting bracket
- Failed low-side driver inside the PCM for this specific output
How to fix it
- Read and save freeze frame data; note oil temperature, rpm and load at the moment the code set
- Inspect the cylinder 2 solenoid connector for oil intrusion, green corrosion and backed-out terminals, and check harness routing for rub-through
- With the key on and engine off, back-probe the control wire and compare the reading with a solenoid on a known-good cylinder
- Unplug the solenoid and test the control wire for a short to battery voltage with the module also disconnected
- Measure the solenoid winding resistance and compare it against the other deactivation solenoids on the same bank
- Verify the ground return path and the fuse or relay feeding the solenoid bank
- Swap the suspect solenoid with an identical unit from another cylinder; if the code follows the part, replace it, otherwise repair the harness. Consider the PCM only after wiring and component tests pass