Cylinder 1 Exhaust Valve Control Circuit Low
Diagnostic trouble code P3407 indicates that the powertrain control module (PCM) has detected a low voltage condition in the control circuit for the cylinder 1 exhaust valve deactivation mechanism. This typically means the circuit is shorted to ground or has excessive resistance, preventing the cylinder deactivation system from operating correctly.
While not usually an immediate safety hazard, driving with this code can lead to poor engine performance, reduced fuel economy, and potential internal engine wear over time. It should be diagnosed and repaired soon to restore proper cylinder deactivation function.
Common symptoms
- Illuminated Check Engine Light
- Engine misfires or runs rough
- Decreased fuel efficiency
- Lack of engine power or sluggish acceleration
- Cylinder deactivation system disabled by the PCM
Likely causes
- Faulty cylinder 1 exhaust valve control solenoid
- Wiring harness damage (short to ground or open circuit) in the control circuit
- Poor electrical connection at the valve control solenoid connector
- Low engine oil pressure or incorrect oil viscosity affecting the deactivation lifters
- Mechanical failure within the cylinder 1 exhaust valve lifter assembly
- Faulty Powertrain Control Module (PCM) (rare)
What to check before replacing parts
Check engine oil level and condition.
Look for: Ensure the oil is at the correct level and is the proper viscosity, as the cylinder deactivation system relies on oil pressure to function. Dirty or low oil can cause this code.
Visually inspect the wiring and connector for the cylinder 1 exhaust valve control solenoid.
Look for: Look for frayed wires, melted insulation, corrosion, or bent pins that could cause a short to ground or an open circuit.
Measure the resistance of the cylinder 1 exhaust valve control solenoid using a digital multimeter.
Look for: Compare the resistance reading to the manufacturer's specifications. An out-of-spec reading indicates a faulty solenoid that needs replacement.
Test the control circuit for a short to ground.
Look for: With the solenoid disconnected and the PCM disconnected, check for continuity between the control wire and ground. Any continuity indicates a short to ground in the wiring harness.
Verify the voltage supply to the solenoid.
Look for: With the key on, engine off (or engine running, depending on manufacturer procedure), check for proper voltage at the solenoid connector. Low or no voltage indicates a wiring issue or a problem from the PCM.
This page explains the generic P3407 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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