P3429Cylinder 4 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
- P3429 stands for an open circuit to an actuator that would switch nothing but cylinder 4's exhaust valves. No manufacturer documents this code publicly, although few cylinders are deactivated as often: GM's AFM V8s (bulletin 20-NA-038), the Hemi with MDS and Mazda CX-5 and Mazda6 four-cylinders with deactivation all idle cylinder 4; Mazda's alert SA-041/18 names cylinders 1 and 4 as the deactivation area where rocker arms can fall out. In the GM design reviewed by NHTSA in 2025, one solenoid per cylinder works the intake and exhaust lifter together, so interrupted wiring is reported as P3425. A layout with a separate exhaust output would still owe CARB a continuity test. P3430 to P3432 complete this exhaust group.
- What you may notice
- Check engine lamp on
- Fuel-saving mode inactive
- Likely causes
- PossibleOpen conductor or pushed-out pin to the cylinder 4 exhaust actuator
- PossibleExhaust actuator coil burnt open
- RareControl module output not switching
- 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.