P2577 code meaning
Direct Ozone Reduction Catalyst Efficiency Below Threshold
Powertrain system Generic code P25xx codes Check engine light
What P2577 means
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.
P2577 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor1 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P2577
- Check engine light on
- No change in engine cooling or performance
- Possible failed emissions inspection
Common causes of P2577
- Most likelyAftermarket radiator without ozone-reducing coating
- PossibleCatalytic coating worn, damaged or covered with dirt
- Less likelyFaulty DOR sensor giving a false result
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Dor catalystRadiator
What each part of P2577 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 5 | Area: vehicle speed, idle control and auxiliary inputs. |
| 77 | The exact fault in that area. |
What to do next
- Note P2577 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P2577
What does P2577 mean?
P2577 means "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. It is a generic code, so it means the same on every make.
Is it safe to drive with P2577?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P2577 fail an emissions test?
Yes, it can. P2577 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P2577 to fix?
Difficulty: medium. A typical repair takes 1 to 3 hours of work. This is a job for a workshop.
Will P2577 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.