P2577 Direct Ozone Reduction Catalyst Efficiency Below Threshold

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.

Likely causes

Symptoms

• Check engine light on
• No change in engine cooling or performance
• Possible failed emissions inspection

Repair estimate

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

Related codes

References: law.cornell.edu, basf.com, basf.com.