P2257 indicates that the powertrain control module has detected a lower-than-expected voltage condition on the secondary air injection system's control circuit. The secondary air injection system helps reduce cold-start emissions by pumping fresh air into the exhaust, and this code means the electrical command path for that system is not reading correctly.
A short to ground, open wire, corrosion, or pin damage in the harness between the PCM and the air injection components is the most common cause of a 'circuit low' code.
The solenoid valve that diverts air to the exhaust may have a shorted or open coil, pulling the control circuit voltage below specification.
A seized, shorted, or internally failed pump motor can draw excessive current or create a low-voltage condition on the control circuit.
A damaged relay, poor relay socket connection, or blown fuse can prevent proper voltage from reaching the air injection system control circuit.
Although uncommon, the PCM's internal driver for the air injection system circuit can fail, but this should only be considered after wiring and components test good.
The definition is universal; the diagnostics are engine-specific. Open your vehicle for the codes documented for it:
Usually yes for normal driving, but emissions will be elevated, cold-start performance may suffer, and the vehicle will likely fail an emissions inspection.
No. P0410 is a general secondary air injection system malfunction, while P2257 specifically points to a low-voltage condition in the system's control circuit.
Usually no. PCM failure is a rare cause of this code. Most cases are caused by wiring shorts, connector issues, failed valves, or pump problems, so those should be ruled out first.
Yes. A blown fuse or faulty relay can prevent the control circuit from reaching normal voltage and trigger this code.