Heated Catalyst Efficiency Below Threshold (Bank 2)
The P0433 code means the vehicle's onboard diagnostic system has detected: Heated Catalyst Efficiency Below Threshold (Bank 2). This is a moderate severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- hard
- Estimated cost
- $400 - $1400 (parts and labor)
Reads enhanced codes and shows real-time O2 sensor data. Verify the cat is actually bad before dropping $1,000+ on a replacement.
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Common Symptoms
- Check Engine Light illuminated
- Sulfur smell from exhaust
- Slight decrease in fuel economy
- Failed emissions test
Probable Causes (Ranked by Likelihood)
- Degraded heated catalytic converter on Bank 2 Very High
- Bank 2 catalyst heater circuit failure High
- Engine misfire contaminating the Bank 2 catalyst Moderate
- Faulty Bank 2 downstream O2 sensor Low
Frequently Asked Questions
Can I drive with code P0433?
Yes. The Bank 2 heated catalyst is underperforming but the vehicle drives normally. Emissions will be higher during cold starts.
Is P0433 the Bank 2 version of P0423?
Yes. P0423 refers to Bank 1 heated catalyst efficiency and P0433 refers to Bank 2. The diagnostic approach is identical but applied to the opposite exhaust bank.
Do I need to replace both bank converters?
Only if both are failing. If only Bank 2 has set a code, replace only the Bank 2 converter. However, if both are similar age, proactive replacement of both may save labor costs.
What actually makes the computer set this catalyst code?
California's OBD II regulation — the rule that defines when an OBD system must set an emissions code — requires the system to flag the catalyst when its conversion capability drops far enough that Non-Methane Organic Gas emissions would exceed 1.75 times the FTP full-useful-life standard (Title 13 CCR 1968.2, section (e)(1.2)). So the code is not reporting that the converter is dead; it is reporting that measured efficiency crossed the line the monitor was calibrated to. This is the threshold the monitor is designed around, not a description of your specific fault — the regulation says what the system must detect, not how to find it on your vehicle.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
-
Check for catalyst heater circuit codes on Bank 2
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Compare Bank 2 upstream and downstream O2 sensor activity
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Verify Bank 2 catalyst heater operation by measuring current draw during cold start
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Check for exhaust leaks and misfire codes on Bank 2
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Replace the Bank 2 heated catalyst if all other checks pass
Sources 3
This page is built from documented references. Verify against your own service info before repair work.
- California Code of Regulations, Title 13 section 1968.2 (OBD II)malfunction criteria, section (e)
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
- Cross-checked against the SAE J2012:2002 DTC table (2026-08-27)archived scan of the SAE standard — readable copy, not SAE’s current edition
Commonly Affected Vehicles
- 2004-2016 Lexus RX 400h
- 2005-2017 Toyota Highlander Hybrid V6
- 2006-2018 Lexus GS 450h
- 2007-2019 Lexus LS 600h
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