Cylinder 4 Deactivation/Intake Valve Control Circuit/Open
The powertrain control module (PCM) has detected an open circuit or electrical fault in the cylinder 4 deactivation/intake valve control circuit. This means the engine computer cannot properly control the intake valve for cylinder 4 during the cylinder deactivation process.
While the vehicle can usually still be driven, the cylinder deactivation system will be disabled. Prolonged driving with this issue can lead to poor fuel economy and potential engine misfires.
Common symptoms
- Illuminated Check Engine Light
- Decreased fuel economy
- Rough engine idle or running
- Engine misfire on cylinder 4
- Slight lack of engine power or hesitation
Likely causes
- Low engine oil level or dirty engine oil
- Faulty cylinder 4 deactivation solenoid
- Corroded or damaged electrical connector at the solenoid
- Open or shorted wiring in the cylinder 4 deactivation circuit
- Restricted oil passages to the deactivation solenoid
- Faulty Powertrain Control Module (PCM)
What to check before replacing parts
Check the engine oil level and condition.
Look for: Look for low oil levels or extremely dirty, sludged oil, which can prevent hydraulic deactivation solenoids from operating properly.
Visually inspect the wiring and connector for the cylinder 4 deactivation solenoid.
Look for: Look for broken wires, melted insulation, backed-out pins, or corrosion that could cause an open circuit.
Test the resistance of the cylinder 4 deactivation solenoid using a multimeter.
Look for: Look for an out-of-spec resistance reading or an open circuit (OL) indicating an internally failed solenoid.
Check for voltage and ground at the solenoid connector while commanding the solenoid via a scan tool.
Look for: Look for proper battery voltage and a good ground; the absence of either indicates a wiring harness or PCM issue.
Perform an active test using a bi-directional scan tool to command the cylinder 4 deactivation solenoid on and off.
Look for: Listen for an audible click from the solenoid and watch for a change in circuit state on the scan tool data to verify mechanical and electrical operation.
This page explains the generic P3425 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
Gear guide: Best OBD2 ScannersRead this code yourself next time — from $20 Bluetooth dongles to bidirectional scan tools.Rather have a pro handle it? Find a vetted local mechanic.