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  • An activated P0429 trouble code indicates a problem in the catalyst heater control circuit.
  • A bad exhaust temperature sensor, malfunctioning catalytic converter, and exhaust leaks are some of the most common reasons why on-board diagnostics can log this code.
  • Other than an illuminated check engine light, the only other symptom for this code is poor fuel economy.

Catalytic converters are one of the most significant emission add-ons ever installed on a vehicle. They reduce tailpipe emissions of carbon monoxide (CO) and hydrocarbons (HC).  However, they could develop issues over time. P0429 is one of the trouble codes related to a fault in the catalyst heater control circuit.

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What Does the P0429 Code Mean?

Diagnostic trouble code (DTC) P0429 stands for “Catalyst Heater Control Circuit Bank 1.” The powertrain control module (PCM) sets it when it detects an issue with the catalytic converter’s heating element.

catalytic converter with issue in heating element
A catalytic converter uses a catalyst to create a chemical reaction that converts harmful exhaust emissions into less harmful substances.

A catalytic converter uses a catalyst to create a chemical reaction that converts harmful exhaust emissions into less harmful substances. These catalysts are usually made up of rhodium, palladium, or platinum. These elements plus the extreme heat of the engine exhaust make the conversion of harmful substances possible.

The PCM logs code P0429 when the exhaust oxygen concentration measured by the upstream and downstream oxygen (O2) sensors is comparable. It could also store the code if it detects an electrical issue with the heated catalyst control circuit.

Note: The definition of code P0429 might be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of the P0429 Code?

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What are the Common Symptoms of the P0429 Code?

How to Diagnose the P0429 Code

DTC P0429 is a generic trouble code, but that does not imply that it has a universal solution. The steps for diagnosing this trouble code might differ depending on the vehicle.

In most cases, you’ll need more than a scan tool to diagnose a P0429 code. You’ll need specific equipment as well as up-to-date technical information about your vehicle’s traction control system. So if you are unfamiliar with vehicle repair and diagnosis, it is best to leave it to a reputable mechanic.

How to Fix the P0429 Code

Attempting to resolve any trouble code can be difficult, and the P0429 code is no exception. If you don’t have the necessary DIY skills and automotive know-how, it’s best to leave the job to a mechanic. Otherwise, you might end up causing more problems with your traction system.

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However,  if you’re an experienced automotive DIYer and you want to do the job yourself, we recommend looking for vehicle-specific information before starting. Guides like those from Chilton or an ALLDATA subscription are helpful.

About The Authors
Written By Automotive and Tech Writers

The Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Contact Center Manager and Technical Reviewer at

William “Bill” Guzenski has produced hundreds of how-to videos for the automotive community. He’s an ASE Certified Master Automobile Technician, and is affiliated with the Specialty Equipment Market Association (SEMA). He loves attending race events and car shows throughout the country, as well as traveling in his 40-foot motorhome, exploring abandoned mines and ghost towns.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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