A faulty direct ozone reduction catalyst deterioration sensor.; Damaged or corroded wiring or connector at the sensor or PCM.; An open or short to ground in the sensor signal circuit.; High resistance in the sensor ground circuit.; A failed powertrain control module, though this is uncommon.; Contamination or physical damage to the sensor element.

DTC codes / P25xx · Vehicle speed, idle control and auxiliary inputs / P2574

P2574Direct Ozone Reduction Catalyst Deterioration Sensor Circuit Low

P2574 indicates that the powertrain control module has detected a low voltage condition on the signal circuit of the direct ozone reduction catalyst deterioration sensor, which is a specialized sensor used on certain vehicles to monitor the catalyst's ability to reduce ozone. The computer compares the sensor's output to an expected range and flags the circuit as low when the voltage stays below the calibrated threshold for a set period.

SystemPowertrain

Code typeGeneric (all makes)

SeverityLow

Fix difficultyIntermediate

AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms.
Possible slight decrease in fuel economy if the system affects air-fuel ratio control.
In rare cases, a rough idle or hesitation if the sensor feedback is used for other control strategies.
No driver-perceptible change in performance in most instances.
Failure to pass an emissions inspection due to the stored code.

Common causes, most likely first

A faulty direct ozone reduction catalyst deterioration sensor.
Damaged or corroded wiring or connector at the sensor or PCM.
An open or short to ground in the sensor signal circuit.
High resistance in the sensor ground circuit.
A failed powertrain control module, though this is uncommon.
Contamination or physical damage to the sensor element.

How to diagnose and fix it

Use a scan tool to verify P2574 is current and check for any related codes.
Visually inspect the sensor and its wiring harness for damage, corrosion, or loose connections.
Measure the sensor signal voltage with a digital multimeter and compare to the manufacturer's specification.
Check the sensor ground circuit for excessive resistance using a voltage drop test.
If the circuit tests good, test the sensor's resistance or output according to the service information.
Replace the sensor if it fails the electrical tests, then clear codes and verify the repair.
If the code persists after sensor replacement, diagnose the PCM and its connectors for faults.

When P2574 is not the sensor's fault

A low voltage code often results from a poor ground connection rather than a failed sensor, so always check ground integrity before condemning the sensor.
The direct ozone reduction catalyst system is specific to certain vehicles, and technicians unfamiliar with it may misdiagnose the code as a generic catalyst efficiency issue.
Wiring harness damage from road debris or heat is a common cause that can be overlooked if only the sensor is replaced.
The sensor may share a ground with other components, so a fault in that shared ground can set multiple codes that seem unrelated.
After repairs, the vehicle may need to complete a specific drive cycle before the monitor runs and the code clears, leading to false comebacks.

Can I keep driving with P2574?

The vehicle is generally safe to drive with this code because it does not affect engine performance or safety systems, but you should avoid long-term driving and address the issue promptly to ensure emissions compliance and prevent potential secondary problems.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.