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DTC codes / P34xx · Auxiliary emission controls / P3425

P3425Cylinder 4 Deactivation/lntake Valve Control Circuit/Open

P3425 indicates that the powertrain control module has detected an open circuit or abnormal electrical condition in the control circuit for the cylinder 4 deactivation/intake valve, which is part of a variable displacement or cylinder management system. The computer monitors the circuit for expected voltage or current and sets this code when the signal falls outside the normal range, preventing the cylinder from deactivating or reactivating as commanded.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaAuxiliary emission controls

Symptoms you may notice

  • Illuminated check engine light, often with no other noticeable symptoms
  • Rough idle or misfire-like shudder when the engine transitions between full and reduced displacement
  • Reduced fuel economy because the cylinder deactivation system remains inactive
  • Slight loss of power or hesitation during light-throttle cruising
  • In some cases, the engine may run rough or stall if the valve control circuit affects intake airflow

Common causes, most likely first

  1. Open or damaged wiring in the cylinder 4 deactivation/intake valve control circuit
  2. Failed cylinder deactivation solenoid or intake valve control actuator
  3. Corroded or loose electrical connector at the valve or solenoid
  4. Faulty powertrain control module driver for that circuit (rare)
  5. Internal short or open in the valve control solenoid coil
  6. Blown fuse or poor ground connection serving the deactivation system

How to diagnose and fix it

  1. Inspect the wiring harness and connector at the cylinder 4 deactivation/intake valve for chafing, corrosion, or loose pins
  2. Check the fuse and ground connections for the cylinder deactivation system
  3. Measure resistance of the deactivation solenoid or actuator and compare to manufacturer specifications
  4. Backprobe the control circuit at the PCM and command the valve on and off with a scan tool to verify signal integrity
  5. Repair or replace any damaged wiring or connectors, then clear the code and retest
  6. If the circuit tests good, replace the faulty deactivation solenoid or intake valve actuator
  7. As a last resort, diagnose the PCM driver circuit and replace the PCM if confirmed faulty

What the code does not always mean

  • A P3425 can be set by a simple loose connector or chafed wire, so always perform a visual and wiggle test before condemning the solenoid or actuator.
  • The code does not necessarily mean the cylinder is permanently disabled; it only indicates an electrical fault in the control circuit, and the engine may still run on all cylinders.
  • Some vehicles use the same circuit for both deactivation and intake valve control, so a fault in the intake valve actuator can mimic a deactivation solenoid failure.
  • After any repair, the cylinder deactivation system may require a relearn or adaptation procedure with a scan tool to restore normal operation.
  • A weak battery or charging system can cause intermittent open-circuit codes in these circuits, so check system voltage first.

Can I keep driving with P3425?

You can usually drive the vehicle with P3425 set, but the cylinder deactivation system will be disabled and fuel economy may suffer. Avoid heavy towing or sustained high-load driving until the fault is repaired, and address the code promptly to prevent potential misfire or catalyst damage.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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