P2573 — Direct Ozone Reduction Catalyst Deterioration Sensor Circuit #

The exact wording of this code may vary depending on the vehicle manufacturer.

• Direct Ozone Reduction Catalyst Deterioration Sensor Circuit (Generic/OEM standard)
• Ozone Reduction Catalyst Efficiency Sensor Circuit Malfunction (Honda/Acura)
• Ozone Catalyst Deterioration Sensor Circuit Fault (Toyota/Lexus)
• Ozone Catalyst Sensor Circuit Range/Performance (Mazda)

Summary of the P2573 Code #

The P2573 diagnostic trouble code (DTC) relates to the Direct Ozone Reduction Catalyst Deterioration Sensor Circuit, a system integral to modern emission controls. This code signals that the engine control module (ECM) has detected an abnormal signal, or lack thereof, from the sensor responsible for monitoring the condition of the ozone reduction catalyst. This catalyst helps convert ozone (O₃) in the exhaust into less harmful oxygen molecules before release into the atmosphere—a key part of meeting stringent emissions standards. When this circuit malfunctions, the ECM may be unable to accurately determine catalyst efficiency, potentially leading to increased emissions and compromised compliance. While not immediately catastrophic, this issue should not be ignored if you want to keep your vehicle running clean and compliant.

Common Symptoms for Code P2573 #

If your vehicle has stored the P2573 code, you might notice little to no difference in daily drivability, as this code is often emissions-related rather than performance-based. However, there are some telltale signs:

• Illuminated Check Engine Light (CEL) or Malfunction Indicator Lamp (MIL)
• Failed emissions test or state inspection
• Stored codes related to emissions or catalyst efficiency
• Possible reduction in fuel efficiency over time
• On rare occasions, a slight sulfur or “rotten egg” smell from the exhaust

Probable Causes for Code P2573 #

Several factors can trigger the P2573 code, with some causes more frequent than others. Understanding these causes helps prioritize your diagnostic steps:

1. Faulty Ozone Reduction Catalyst Deterioration Sensor (sensor failure or aging)
2. Wiring issues in the sensor circuit (corrosion, open/short circuits, damaged connectors)
3. Failed or deteriorated ozone reduction catalyst (physical or chemical breakdown)
4. ECM/PCM software error or internal ECM fault (rare)

Step-by-Step Diagnostic for P2573 #

Diagnosing this code requires a systematic approach to avoid unnecessary parts replacement. Here’s a proven procedure for professional and DIY technicians alike:

• Verify the code with a reliable OBD-II scanner and check for other related DTCs.
• Inspect the ozone reduction catalyst deterioration sensor wiring and connector for damage, corrosion, or loose pins.
• Test the sensor using a digital multimeter, following the OEM’s specific resistance and voltage guidelines.
• Check catalyst condition physically if accessible (look for melting, discoloration, or contamination).
• Review live data from the sensor to see if it’s responding to engine operation as expected.
• Clear the code and perform a road test to see if it returns.
• If all external checks pass, consider ECM/PCM diagnostics or software updates as per OEM technical service bulletins.

Possible Repairs for P2573 #

Once you’ve pinpointed the cause, the following repairs are typically effective for resolving P2573:

• Replace a faulty Ozone Reduction Catalyst Deterioration Sensor
• Repair or replace damaged wiring/connectors in the sensor circuit
• Replace the ozone reduction catalyst if it’s physically or chemically deteriorated
• Reflash or replace the ECM/PCM if a software or internal fault is confirmed

Is it Safe to Drive with Code P2573? #

Yes, you can generally continue to drive with a P2573 code, but it’s not recommended for an extended period. The main risk is failing an emissions inspection and possibly causing long-term harm to your vehicle’s emission system. Ignoring this code for too long could lead to further catalyst damage or higher emissions, which may be illegal in some regions. If other codes or symptoms accompany P2573, have your vehicle checked promptly.

Vehicles Most Commonly Affected by P2573 #

This code appears most often in vehicles equipped with advanced emission systems, particularly in models from the early 2010s onward. The following makes and models are commonly associated:

• Honda (Accord, CR-V, Civic, Odyssey, Pilot)
• Toyota (Prius, Camry, Highlander, RAV4)
• Lexus (ES, RX, NX hybrids)
• Mazda (CX-5, Mazda3, Mazda6)
• Other brands with direct ozone reduction catalysts as part of OEM emissions strategy

Frequent Mistakes & Best Practices for P2573 #

Misdiagnosis is surprisingly common with P2573, especially when technicians overlook basic checks or skip straight to component replacement. To avoid headaches and extra costs, keep these points in mind:

• Don’t replace the catalyst before confirming the sensor and wiring are in good condition.
• Always check for technical service bulletins (TSBs) related to P2573 for your specific make/model.
• Don’t ignore other codes that may point to related or root causes.
• Use only OEM or OEM-equivalent sensors and components for replacement.
• Document your diagnostic steps for future reference or warranty claims.

Quick FAQ for P2573 #

Is P2573 covered under my emissions warranty?
In many cases, yes. Most manufacturers cover emissions components, including sensors and catalysts, for up to 8 years or 80,000 miles. Check your owner’s manual or contact your dealer for specifics.

Can a bad battery or charging system trigger P2573?
While rare, low voltage or charging issues can cause false sensor readings. Always check your vehicle’s electrical health before replacing expensive components.