P3429 code meaning
Cylinder 4 Exhaust Valve Control Circuit/Open
Powertrain system Generic code P34xx codes Check engine light
What P3429 means
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.
P3429 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P3429
- Check engine lamp on
- Fuel-saving mode inactive
Common causes of P3429
- PossibleOpen conductor or pushed-out pin to the cylinder 4 exhaust actuator
- PossibleExhaust actuator coil burnt open
- Less likelyControl module output not switching
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Cylinder deactivation solenoidWiring harnessECM
What each part of P3429 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 3 | Mixed range: generic and manufacturer-specific codes. |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| 29 | The exact fault in that area. |
What to do next
- Note P3429 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P3429
What does P3429 mean?
P3429 means "Cylinder 4 Exhaust Valve Control Circuit/Open". P3429 stands for an open circuit to an actuator that would switch nothing but cylinder 4's exhaust valves. It is a generic code, so it means the same on every make.
Is it safe to drive with P3429?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P3429 fail an emissions test?
Yes, it can. P3429 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P3429 to fix?
Difficulty: medium. A typical repair takes 0.5 to 4 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P3429 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.