P3457 indicates that the control circuit for the intake valve deactivation solenoid on cylinder 8 is open, meaning the PCM cannot command the solenoid to close the intake valve during cylinder deactivation. This prevents the Active Fuel Management system from operating on that cylinder.
A broken wire, corroded terminal, or disconnected connector prevents the PCM signal from reaching the solenoid.
The solenoid coil may be open internally, so it cannot be energized even when voltage is present.
Moisture or debris can cause high resistance or an open connection at the solenoid plug.
Internal driver transistor in the PCM may be open, but this is uncommon compared to wiring or solenoid faults.
PCM failure is rare for this code; the majority of cases are caused by wiring, connector, or solenoid issues. Replace the PCM only after all other possibilities have been ruled out.
The vehicle will run, but cylinder 8 deactivation will be disabled, leading to lower fuel economy and slightly higher emissions. It is advisable to repair the fault promptly.
Clearing the code only removes the stored fault; the underlying open circuit will cause the code to return until the physical fault is repaired.
Yes, the deactivation system improves fuel efficiency and reduces emissions; a fault can cause the vehicle to fail emissions testing in jurisdictions that monitor it.