P2257AIR System Control A Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P2257 concerns the control circuit of the secondary air (AIR) pump or its relay, which blows fresh air into the exhaust during cold starts so the catalyst lights off sooner. The code sets when that circuit reads low. GM's 2018 tables (LWE section) watch the low-side driver of the AIR pump control: a resistance of 0.5 ohm or less to controller ground, detected as low voltage with the driver switched off, in 20 of 25 samples of 250 ms with at least 11 V on the powertrain relay, Type B; some controllers also log P0418. VW's 2014 specification books for the CC and Touareg flag a relay control voltage between 0 and 3.26 V. P2258 is the short to power, P0418 the open circuit. Affected cars mainly emit more during warm-up.
- What you may notice
- Check engine light
- Secondary air pump silent during cold start
- Secondary air flow codes such as P0411 may follow
- Likely causes
- LikelyRelay control wire shorted to ground
- PossibleSecondary air relay with a shorted coil
- RareWater ingress in the relay or pump connector
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €30 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.