P2577: Direct Ozone Reduction Catalyst Efficiency Below Threshold

What it means

This code indicates Direct Ozone Reduction Catalyst efficiency below the calibrated threshold. It does not establish the specific reason for reduced efficiency.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The DOR catalyst is part of the system intended to reduce ozone, and the engine control module monitors its effectiveness using the system's sensor inputs. P2577 sets when the calculated DOR catalyst efficiency falls below the module's calibrated threshold; the code does not identify the cause on its own.

Common causes

Most likely first.

1. DOR coating worn off the radiator
2. Coating contaminated by salt and grime

Symptoms

• Check engine light

How to diagnose it

1. Review freeze-frame data and related DOR sensor codes to confirm the conditions when the efficiency monitor failed.
2. Check for faults in the DOR temperature and deterioration sensor circuits, since invalid inputs can undermine the efficiency assessment.
3. Inspect the radiator-mounted DOR catalyst surface for visible coating damage or contamination such as accumulated salt and grime.
4. Check that the DOR sensor readings respond plausibly under the conditions described in the freeze-frame data.
5. After correcting any input faults or visible contamination, reassess the efficiency result using the vehicle's specified diagnostic procedure.

Common fixes

• Remove accessible salt and grime from the DOR catalyst surface using a method approved by the vehicle manufacturer.
• Repair any DOR sensor-circuit faults found during diagnosis.
• Correct damaged or missing catalyst coating only if the manufacturer provides an approved repair.
• Replace the affected catalyst or radiator assembly if its DOR coating is confirmed to be deteriorated and is not serviceable separately.

Can I keep driving?

The stated symptom is a check-engine light, and no limp mode is indicated, so driving is generally possible if the vehicle behaves normally. The ozone-reduction function may be below its monitored threshold until the cause is corrected.