What does it mean?
P3421 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Cylinder 3 Exhaust Valve Control Circuit/Open . 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) on and the variable exhaust valve strategy disabled
- Engine feels lazy and lacks pull as rpm rises
- Rough or unsettled idle with an uneven exhaust note
- Ticking from the valve train near cylinder 3
- Fuel consumption above normal, sometimes with a cylinder 3 misfire
- Hesitation during acceleration in the mid range
Likely causes
- Solenoid connector unplugged, poorly latched or with a terminal pushed out of the housing
- Broken control wire or a break hidden inside the insulation after chafing
- Oil wicking through the harness and coating the terminals so they no longer make contact
- Open coil inside the exhaust valve control solenoid
- Loss of the supply feed to the valve control solenoid group, such as a blown fuse
- Damaged connector body from heat near the exhaust side of the head
How to fix it
- Save the freeze frame, then check whether the code is present now or only under certain conditions
- Unplug the solenoid and inspect the terminals closely for oil film, corrosion and push-back
- Measure coil resistance at the solenoid; an open circuit reading condemns the solenoid
- Check continuity of the control wire back to the module connector, and confirm the supply feed with the key on
- Wiggle test the harness branch while watching the meter for momentary opens
- Check the fuse and any relay supplying this solenoid group
- Repair the wire or terminal, or replace the solenoid, then command the output through the scan tool to verify the circuit responds