OBD-II code P3479 indicates that the engine control module (PCM/ECM) has detected a low voltage condition in the exhaust valve control circuit for cylinder 10. This code is set on engines equipped with variable valve timing (VVT), variable valve lift, or cylinder deactivation systems that use electronically controlled oil or solenoid-actuated exhaust valves per cylinder. The 'Low' designation typically means the circuit voltage has dropped below the manufacturer's calibrated threshold, often due to an open, short to ground, or excessive resistance somewhere in the circuit.
The exhaust valve control solenoid for cylinder 10 is the most common failure point. Internal coil failure, contamination from oil debris, or normal wear can cause the solenoid to draw abnormal current or produce low circuit voltage.
Wiring chafing, heat damage, oil contamination, or a loose/corroded connector at the solenoid or PCM can introduce high resistance or an open circuit, triggering a low-voltage reading. Inspect for broken wires, spread pins, and water intrusion.
Many VVT and deactivation systems rely on oil pressure to actuate valves. Insufficient oil pressure, a clogged oil control passage, or degraded oil can prevent proper solenoid operation and may cause circuit faults that present as low voltage.
A partially stuck oil control valve, a clogged oil passage leading to the exhaust cam phaser or deactivation solenoid for cylinder 10, or a weak cam phaser can trigger the code even when electrical components are intact.
If the overall electrical system voltage drops below normal during operation, the PCM may interpret solenoid circuit voltage as abnormally low, setting the code without a true component failure.
The engine control module itself is an unlikely cause for P3479. Internal driver failures are possible but uncommon; replacement of the PCM should only be considered after all wiring, connectors, oil pressure, and solenoid tests rule out other causes.
Short-term driving is usually possible, but the engine may run roughly, lose power, or use more fuel. Prolonged driving can lead to catalytic converter damage or additional misfire codes, so diagnosis is recommended as soon as practical.
No. While the solenoid is a common failure, low-voltage codes are frequently caused by wiring faults, connector problems, or oil pressure issues. The solenoid should be tested before replacement.
Almost never. Drivers are sometimes told to replace the engine computer for low-voltage circuit codes, but P3479 is far more often caused by the solenoid, its wiring, or oil pressure problems. Replacing the PCM without first testing those components usually wastes money.
Yes, on engines with cylinder deactivation or variable valve lift, this code points to the control circuit for the exhaust valve actuator on cylinder 10. The same general diagnostic approach applies regardless of the specific valve actuation technology used.