Powertrain, shared range

P3429 Cylinder 4 Exhaust Valve Control Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

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.

Likely causes

Open conductor or pushed-out pin to the cylinder 4 exhaust actuator
Exhaust actuator coil burnt open
Control module output not switching

Symptoms

  • Check engine lamp on
  • Fuel-saving mode inactive

Repair estimate

DifficultyMediumDIY possible
Parts and labour€60–900
Time0.5–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

cylinder deactivation solenoidwiring harnessecm

Related codes

P3430P3431P3432P3425P3421P3437

References: law.cornell.edu, static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov.