DTC codes / P25xx · Vehicle speed, idle control and auxiliary inputs / P2571
P2571 indicates that the powertrain control module has detected an intermittent or erratic signal from the direct ozone reduction catalyst temperature sensor, which monitors the temperature of a specialized catalyst used to reduce ozone-forming emissions. The circuit voltage or resistance is jumping unpredictably rather than holding a steady value, so the computer cannot trust the sensor's readings.
Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.
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