P2577Direct Ozone Reduction Catalyst Efficiency Below Threshold
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- P2577 means the OBD system has concluded that the direct ozone reduction (DOR) catalyst - usually a radiator coated with an ozone-destroying catalyst such as BASF's PremAir - no longer converts enough ozone. CARB ties the threshold to the credit claimed: for LEV III/IV vehicles with a DOR credit of 5 mg/mi NMOG or less, a malfunction is a system with no measurable ozone reduction left; above 5 mg/mi, it is a performance loss worth more than 5 mg/mi of credit. Earlier non-LEV III cars used 50 % of the NMOG standard instead. No manufacturer publicly documents P2577. Plausible causes are a non-coated aftermarket radiator or a coating worn or fouled by dirt; the usual fix is the correct coated radiator. Driving is unaffected.
- What you may notice
- Check engine light on
- No change in engine cooling or performance
- Possible failed emissions inspection
- Likely causes
- LikelyAftermarket radiator without ozone-reducing coating
- PossibleCatalytic coating worn, damaged or covered with dirt
- RareFaulty DOR sensor giving a false result
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €150 – €1,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.