The Culprit of Catalytic Converter Failure

Poor vehicle maintenance

No matter who you are, if you own a vehicle, any kind of vehicle , you must do intermittent maintenance (or have it done by a professional technician). It can seem like the maintenance is incessant, which is because there are so many moving parts and pieces that don’t always need fixing or replacing at the same time as others. Regardless of whether we do the work ourselves or take our vehicle into a shop, air filters must be changed if dirty, the right fuel must be used, and the oil must be changed on schedule, especially after being in some severe driving conditions or taking many short trips. Falling off track with these maintenance musts is a recipe for having yourself an inefficient catalytic converter.

Eventually, a combination of these conditions can increase carbon accumulation in the combustion chamber, leading to higher combustion temperatures and compression ratios. The result?  Excessive NOx output by the engine.

Combine excessive NOx output with carbon fouling of the spark plugs and O2 sensors with the contamination or fouling of the catalytic converter and you have the ingredients for an emissions systems failure. In short, the catalyzing metals in the converter are no longer exposed to the exhaust gases, and the converter is rendered inactive. When it gets bad enough, it can actually make a vehicle stop running!

The deactivation of the catalytic converter causes a reduction of O2 storage, which is detected by the O2 sensor, resulting in a PO420 diagnostic trouble code.

Thermal Failure

A converter can be destroyed by excessive heat. Since there are no moving parts in a converter, the usual suspect is fuel contamination, the result of an engine operating system failure or malfunction.

When the vehicle is running in a rich air-fuel mixture condition, unspent or raw fuel (HC) along with carbon monoxide (CO) is pumped into the converter through the exhaust system.

The oxidation (or burning process) of the raw fuel continues unchecked, raising the internal temperature of the converter to a point where the converter matting and substrate are destroyed.

The conditions of “thermal failure” prohibit the converter from storing oxygenthus setting off a PO420 diagnostic trouble code.


What are the signs?

-Engine light on (P0420 or a P0430 are the two inefficient codes on the diagnostic)

-Losing mileage

-Losing power

-Can’t reach highway speeds

-Sound of rocks in an empty can (due to overheating of thermal blanket in converter)

2 Options to fix a Failed Catalytic Converter

Catalytic converters come in two basic forms, either a universal application or a direct-to-fit/vehicle-specific application. The most cost-effective way to go is to replace it with a universal application, if available. On the hand, a vehicle-specific application will cost more.

All original equipment catalytic converters carry an 8 year/80,000 mile federally mandated warranty (whether you are the original owner of the vehicle or not). So, if you have, for example, 75,000 miles on your vehicle, and you suspect you have a catalytic converter problem, by all means, take it in to be checked by the dealership for your make and model vehicle. Don’t take it to an aftermarket auto shop when you can use the warranty!

Aftermarket auto part shops offer 2-year manufacture defect warranties on catalytic converters. This is also federally mandated.  Most dealerships only give a 1-year warranty for replacements. Not to mention, an OE replacement at a dealership could cost you twice as much!

Again, the lack of maintenance on the vehicle is the ultimate problem, NOT the catalytic converter. The catalytic converter has no moving parts! It’s essentially a pollution filter.

Keep in mind also, any time your check engine light comes on, the best practice is to IMMEDIATELY have your vehicle checked by a reputable technician.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s