P2257
AIR System Control A Circuit Low
Auxiliary emissions control (secondary air)
Generic OBD-II
Low
What it means
P2257 means the PCM detected low voltage (an open or short-to-ground) in the secondary air injection system's 'A' control circuit. The secondary air system pumps air into the exhaust after a cold start to help the catalyst warm up and cut emissions, so this is primarily an emissions fault. The car usually still drives normally; a failing control solenoid, pump relay, or wiring are the common causes.
Low
Can I keep driving? Generally safe to drive — mostly an emissions fault, though you may notice brief cold-start hesitation; fix it to pass emissions.
Common symptoms
What you'll notice
- Check-engine light on
- Possible hesitation on acceleration, mainly right after a cold start
- Often no noticeable driving symptom
- Emissions-test failure
Common causes
Most likely first
- Low voltage (open or short-to-ground) in the secondary air injection 'A' control circuitLikely
- Faulty air control solenoid or vacuum controlCommon
- Faulty secondary air pump or pump relayCommon
- Wiring open, shorted, or corroded to the control solenoid/pumpLess often
- System restricted or plugged with carbonLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and inspect the secondary-air control solenoid/pump connector and wiring.
- Check the control circuit for an open or short-to-ground against spec.
- Test the air control solenoid and pump relay for correct operation.
- Inspect vacuum lines and check valves (on vacuum-controlled systems).
- Repair the wiring or replace the failed solenoid/relay/pump, then re-test.
FAQ
Quick answers
Is it safe to drive with P2257?+
Usually yes — the secondary air system mainly affects cold-start emissions, so the car drives normally, but it should be repaired to pass emissions.
Can I just clear P2257?+
It clears, but returns if the control circuit or component fault remains; it will also block an emissions test until fixed.
Related codes
Often seen with P2257
Read & clear P2257 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX