We are all too familiar with this scenario: You replace the catalytic converter on a vehicle and the Check Engine Light (CEL) comes on.  To the customer, it appears that you, the mechanic, are at fault for poor quality work or installing faulty parts.  The customer feels they should have taken it elsewhere, and your reputation is damaged.
 
We agree that nothing is as difficult to resolve as warranty issues.  That is why we are offering solutions to these problems so that you will have fewer warranty problems, and your customers will be satisfied.  To cover this, we feel that you need to be informed about the vehicles and how they operate, so that you can accurately fix the problem.
 
We have put together a list of things that can be done to do the job right, and to minimize problems with your new catalytic converter.
 

1
Make sure to install a converter that is certified for the application.  Most aftermarket converters are certified by displacement and GVW ratings, but this does not always make them suitable for every application.  Common sense must be applied to determine the suitability of a converter for a given application.  One cannot install a round body universal into a full size truck and expect it to work.  Likewise, using regular universal converters in a GM car with a 3.1L or 3.4L is a recipe for disaster.  Careful planning must be employed to determine the correct converter to use.  For the troublesome vehicles, use heavy duty units or suitable aftermarket assemblies that have been tested to work effectively in the intended application.
 

2
 Replace the O2 sensors.  Most O2 sensors are designed to be replaced every 50-80 thousand miles.  If the vehicle has more miles than that, the O2 sensors should be replaced.  Also, if the vehicle has a Mass Air-Flow sensor, it should be thoroughly cleaned.

3
 De-carbon the vehicle.  This is a particularly important step, and is becoming more important due to the increased sensitivity of OBD-II cars.  What happens is the carbon absorbs, then slowly releases oxygen, such that the fuel does not burn completely, and the O2 sensors simultaneously read a lean condition.  The ECU enriches the mixture till the O2 reads correctly, but the vehicle is actually running excessively rich.  Often, doing a de-carbon treatment (B-12, Sea foam, etc.) through a vacuum line, or doing a carb-vac or similar treatment will resolve these issues.  Cleaning or replacing pipe and other exhaust components that have an excessive carbon build up is required.
 

4
 Check the ignition timing.  This is often neglected because most newer cars do not have adjustable timing, but checking it can reveal misfires or faulty sensors.  This is relatively easy to do on most cars.  Excessive ignition advance can lead to excessive Knox emissions, and insufficient advance can lead to excessive Hydrocarbons.


5
 Perform an emissions test.  This is often neglected because newer cars monitor their own emissions.  However, the O2 sensor on a car does just that.  It monitors O2 levels.  A proper IM testing device monitors actual HC, CO, CO2, and Nox emissions and can help isolate any problems. Any unusual readings, such as high Nox or CO can suggest what areas might be causing the trouble.
 
 
 
 
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We have additional information regarding troublesome applications that we feel that you should know about so that you can better serve your customer.  We will begin with the common ones.


GM Trucks.  GM trucks equipped with the 5.7L Vortec engine from 1996 through 1999 equipped with the factory tow package (most are) have questionable computer programming.  Suggestions to correct this problem are: Good high quality converters.  We offer a line of converters for these applications that have an extremely low failure rate.  Secondly, replacement of all O2 sensors.
4.3L, 4.8L, 5.0L, and 5.3L equipped models from 1999 - 2005 are equipped from the factory with cats that are too small to meet the needs of towing and hauling heavy loads. The original cats are small 4" diameter round converters, which overheat when the vehicle is operating under load. We recommend replacing these with larger freer flowing converters that are more suitable for trucks. We also carry bolt on assemblies which are designed to meet the flow requirements of these trucks. Many other aftermarket replacements, especially those made from stainless steel, break behind the driver side flange. Our part is designed to resist thermal and physical stresses, and will not break.
 

GM cars and minivans with the 3.1L , 3.4L , or 3.8L engines require special high-efficiency cats, especially on the California and LEV(Low Emission Vehicle) models.  The solution is to use converters that meet Low Emission Vehicle requirements.
 

Volkswagen cars equipped with the 2.0L engine manufactured for 1998 - 2003 model years.  These cars were manufactured with faulty MAF sensors, which caused damage to both the O2 sensors and the catalytic converters.  Replace these units only with a Low Emission Vehicle compliant converter, and at the same time, replace the O2 sensors and the MAF sensor.  Chances are the MAF sensor was already replaced previously, but it is an inexpensive part, and serves as a little insurance.  We carry replacement weld-in converters and assemblies that meet LEV standards.  The original converters on these cars have a high failure rate on the converter substrate breaking apart.  Our converter is guaranteed not to fail for a period of 5 years or 50,000 miles.  A de-carbon treatment is also highly recommended.


Mazda Protégé and 626 models from 1996 to 2002 have a history of catalyst-related problems.  It is common for most converters to loose some efficiency over time.  All OBD-II vehicles are designed to trigger a CEL and set a code if the converter drops below a certain efficiency. These particular cars often drop below this critical point and fail without warning, often with no fuel management issues.  Our solution is to perform all regular service, including new O2 sensors, and a decarb if the vehicle has very many miles on it.  We have an aftermarket replacement that is designed to operate at higher efficiency. It boasts greater catalyst content, as well as a stainless steel body.  This particular unit has one of the lowest failure rates in the industry.   We offer a 2 year, 25,000 mile warranty on the catalyst, and 5 year 50,000 mile warranty on the stainless steel body.  For some model years, an aftermarket replacement is not yet available.  In these cases, we offer a high efficiency remanufactured unit.  It carries the same warranty as the above listed aftermarket unit.
 
 
 

Honda Civic CX, LX and DX models made from 1997 to 2000 have a converter with a build in manifold that cracks, causing various converter related codes to be set.  The cracks are often not repairable, and repairs are often expensive.  Many repairs also fail.  The manifold is made from cast iron, making it difficult to weld. The OEM part  is expensive and will eventually fail in the same manner.  Our current solution is a one-piece steel manifold and converter set.  It is of the highest available quality, and resolves the issue.  You will also find our cost to be competitive with other lower quality units.  Our warranty is 5 year 50,000 miles on the ceramic biscuit, and 5 year 50,000 miles on the body and manifold. Avoid 2 piece manifold converter sets, or units that have cast manifolds.
 

Honda Accord EX, LX, SE with the 3.0l engine and the Honda Odyssey with the 3.5l from 1999 and newer require very high efficiency Low Emission compliant converters.  These vehicles have special requirements.  They have O2 sensors in the middle portion on the converter body and typical aftermarkets are not efficient enough to pass the vehicle's self-diagnostics.  The O2 sensors should be replaced, and the EGR system should be checked for proper operation. Additionally, the engine should be de-carboned to optimize its performance. 

Many Toyota vehicles meet Low Emission Vehicle requires. These vehciles require specialized replacement cats that are efficienct enough to keep the CEL off. Standard tune up procedures should be followed, including new O2 sensors every 50,000 - 80,000 miles.

Bear River Converters
We are the catalytic converter experts!
Selling superior quality converters, flex pipe, and stainless tips.
Check out our eBay store!

We carry an extensive line of premium quality converters. If you need a converter, we will get it for you!
This guide was written by Bear River Converters, the catalytic converter experts. To find a complete line of premium quality converters, flex pipe, and stainless steel tips, visit our eBay store here.
To contact us:
Bear River Converters
1877 W. Park Avenue
Riverton, UT 84065

Web: www.bearriverconverters.com
Phone: 888-782-8825 (Toll Free)
Fax: 801-446-4511
E-mail: brc@bearriverconverters.com