P3421Cylinder 3 Exhaust Valve Control Circuit/Open
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P3421 opens the exhaust group of cylinder 3 and stands for an interrupted circuit to an actuator that would switch only the exhaust valves. No manufacturer documents this code publicly. Engines that are known to idle cylinder 3, such as GM's LTA and LT2 V8s (bulletin 20-NA-038) and the L84, let one lifter control both valves of the cylinder, so an open circuit there shows up as P3417. A GM patent application on deactivation hardware keeps a single oil-switching valve and only shapes the cam timing so that the exhaust side drops out first and returns first. Should a design ever give the exhaust side its own actuator, CARB's continuity check for outputs would apply to it. The owner would see a warning lamp and lose the economy mode.
- What you may notice
- Check engine lamp on
- Cylinder deactivation locked out
- Likely causes
- PossibleBroken lead or loose terminal at the cylinder 3 exhaust actuator
- PossibleExhaust actuator winding interrupted
- RareFault in the control module output
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €60 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.