Cylinder 4 Exhaust Valve Control Circuit/Open
Diagnostic trouble code P3429 indicates that the powertrain control module (PCM) has detected an open circuit or malfunction in the exhaust valve control circuit for cylinder 4. This code is typically associated with cylinder deactivation systems, where the PCM cannot properly control the exhaust valve actuator for that specific cylinder.
While the vehicle can usually still be driven, the cylinder deactivation system will be disabled, leading to reduced fuel economy and potential drivability issues. It should be diagnosed and repaired soon to restore full system functionality and prevent further engine management complications.
Common symptoms
- Illuminated Check Engine Light
- Decreased fuel efficiency
- Engine misfire or rough running
- Lack of engine power
- Cylinder deactivation system disabled
Likely causes
- Faulty cylinder 4 exhaust valve control solenoid/actuator
- Wiring harness damage (open or shorted) in the cylinder 4 exhaust valve circuit
- Poor electrical connection at the valve control solenoid
- Low engine oil pressure or incorrect oil viscosity affecting actuator operation
- Mechanical failure within the cylinder 4 lifter or valve train
- Faulty Powertrain Control Module (PCM) (rare)
What to check before replacing parts
Check engine oil level and condition.
Look for: Low oil level, dirty oil, or incorrect oil viscosity can prevent proper operation of the hydraulic cylinder deactivation components. Ensure oil is full and clean.
Visually inspect the wiring harness and connector for the cylinder 4 exhaust valve control solenoid.
Look for: Look for frayed wires, melted insulation, corrosion, or loose pins at the connector that could cause an open circuit.
Measure the resistance of the cylinder 4 exhaust valve control solenoid using a multimeter.
Look for: Compare the resistance reading to the manufacturer's specification. An infinite reading (OL) indicates an internal open circuit in the solenoid, requiring replacement.
Check for voltage and ground at the cylinder 4 exhaust valve control solenoid connector with the key on, engine off (or as commanded by a scan tool).
Look for: If the specified voltage or ground is missing, there is a wiring issue between the PCM and the solenoid, or a blown fuse/relay.
Use a bi-directional scan tool to command the cylinder 4 exhaust valve solenoid on and off.
Look for: Listen for a click from the solenoid or monitor the circuit state on the scan tool. If it does not respond despite having good power and ground, the solenoid is likely faulty.
This page explains the generic P3429 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.
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