Cylinder 3 Exhaust Valve Control Circuit Low
Diagnostic trouble code P3423 indicates that the powertrain control module (PCM) has detected a low voltage condition in the control circuit for the cylinder 3 exhaust valve deactivation mechanism. This typically occurs in vehicles equipped with cylinder deactivation (variable displacement) systems when the PCM commands the exhaust valve to deactivate but the circuit voltage falls below the expected threshold.
While the vehicle will usually remain drivable, the cylinder deactivation system will be disabled, leading to reduced fuel economy. It should be diagnosed soon to prevent potential internal engine wear or drivability issues.
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 3 exhaust valve control solenoid
- Low engine oil level or poor oil pressure
- Wiring harness damage, short to ground, or open circuit in the solenoid control circuit
- Corroded or loose electrical connector at the solenoid
- Restricted oil passages to the valve lifter/solenoid
- Faulty Powertrain Control Module (PCM) (rare)
What to check before replacing parts
Check the engine oil level and condition.
Look for: Ensure the oil is at the correct level and is clean. Low or dirty oil can prevent the hydraulic cylinder deactivation system from operating correctly.
Visually inspect the wiring and connectors for the cylinder 3 exhaust valve control solenoid.
Look for: Look for frayed wires, melted insulation, or corroded pins that could cause a short to ground or an open circuit.
Test the resistance of the cylinder 3 exhaust valve control solenoid using a multimeter.
Look for: Compare the resistance reading to the manufacturer's specifications. An out-of-spec reading indicates an internally failed solenoid.
Check for voltage and ground at the solenoid connector with the key on, engine off (or commanded via scan tool).
Look for: Verify that the PCM is sending the correct control voltage and that the ground circuit is intact. Lack of voltage suggests a wiring issue or PCM fault.
Perform an engine oil pressure test.
Look for: Verify that the engine oil pressure meets the manufacturer's minimum specifications, as the deactivation system relies on adequate hydraulic pressure to function.
This page explains the generic P3423 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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