Catalyst Heater Control Circuit (Bank 1)
The P0429 code means the vehicle's onboard diagnostic system has detected: Catalyst Heater Control Circuit (Bank 1). This is a low severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- $100 - $500 (parts and labor)
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What Are the Symptoms of P0429?
- Check Engine Light illuminated
- Higher cold-start emissions
- No noticeable drivability issues
- Failed emissions test
What Causes P0429? (Most Likely First)
- Failed catalyst heater relay or fuse Very High
- Open or shorted heater control wiring High
- Failed catalyst heater element Moderate
- ECM heater control driver fault Low
Can I Still Drive with P0429?
Yes, but fix soon. P0429 is rated low severity. It is not an immediate stop-driving fault, but it will not clear itself — book the repair rather than ignoring the light.
Frequently Asked Questions
Can I drive with code P0429?
Yes. The catalyst heater circuit fault only affects cold-start catalyst warm-up. Normal driving and engine performance are not impacted.
Is P0429 only found on hybrid vehicles?
P0429 is most common on hybrid vehicles because they rely on electric catalyst heaters. Some conventional vehicles also use heated catalysts, particularly those meeting SULEV emissions standards.
Can I check the heater element myself?
Yes. With the connector disconnected, measure resistance across the heater terminals. A reading matching the specification (typically 2-10 ohms) indicates the element is intact. An open reading means it has failed.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose P0429?
-
Check the catalyst heater fuse and relay first
-
Measure heater element resistance -- compare to specification (typically 2-10 ohms)
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Verify the ECM is commanding the heater circuit on during cold start
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Check for voltage at the heater connector during cold start
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Inspect wiring from ECM to heater element for damage or breaks
Sources 2
This page is built from documented references. Verify against your own service info before repair work.
- 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
Which Vehicles Commonly Get P0429?
- 2004-2016 Toyota Prius
- 2005-2017 Lexus CT 200h
- 2006-2018 Toyota Highlander Hybrid
- 2007-2019 Toyota Camry Hybrid
- 2008-2018 Ford Fusion Hybrid
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