GMC Sierra 2500 HD Catalytic Converters

The Powertrain Control Module (PCM) or computer is designed to monitor all the emission components on the vehicle amongst other things. When a component is operating outside its pre-determined parameters, the PCM records this information and alerts the driver of the vehicle that a problem may exist by illuminating the warning light or Check Engine Light (CEL).

By definition, P0420 code reads “bank one Catalyst Efficiency low”.  A vehicle displaying this code indicates that something is causing the converter to operate out of specification. Further diagnostics and/or inspection is required before determining the part is defective.

Not necessarily. The Oxygen Sensors are an integral part of the engine management and emissions systems. They should be tested to confirm they are operating properly and replaced if damaged or not within specification.

All California emissions compliant vehicles will be identified on the Vehicle Emissions Control Information (VECI) label located under the hood of the vehicle in the engine compartment.

EFN stands for “Engine Family Number”. It is found on the emissions control tag underneath the hood of your vehicle. This number is needed to ensure the correct part is provided for your California compliant vehicle. It is illegal to equip a registered California or New York vehicle with a federal and/or non-California compliant part. For more information, please visit the following page.

You can start your search here where you’ll provide your vehicle information, including year, make, model and sub-model. If you have further questions, please contact our technical department here.

Standard grade products are manufactured with the required precious metals to be compliant with a properly tuned and operating vehicle.

HM and OEM grade products are designed to function with the Engine Family Number specific designs calling for more precious metals to be used. HM and OEM grades ensure both tailpipe and engine management system compliance is adhered to, while keeping the “check engine light” off. In addition, the extra loading of precious metals will allow for proper engine management interaction and provide additional emissions conversion for vehicles which may not be running at 100%.

Both options will perform equally. Direct-fit parts are easier to install as they are designed to be bolt-on with zero welding required. Universal parts will require professional installation that may include cutting and welding in order to fit. To check the available parts for your vehicle, please start yoursearch here. If you have additional questions, you can contact us here.

Catalytic Converter shape and size is not dictated by any form of legislation or by any current rules. Often time competitors may use non-stock shapes simply because they lack the appropriate design to facility near original fitment. MagnaFlow offers the most number of catalytic converter body configurations and shapes of any other manufacturer available today and considers installation and proper functionality in body selection.

MagnaFlow’s warranty policy is stringent due to a number of factors. Moreover, this is to ensure that the products designed are used in the proper fashion and to reduce unnecessary “redo” work at the shop level. The overwhelming majority of catalytic converter failures are caused by engine related problems which have gone unchecked. Warranty claims are monitored by Emissions governing bodies and high rates of return due to misdiagnosis or no diagnostic can affect continued EO validity.

No, it will not. It is illegal for a dealer, installer or manufacturer to deny you the OE warranty because you’ve changed the exhaust system. Please refer to the Magnuson Moss Warranty Act of 1975, 15 USC, 2302 and Clean Air Act 42 of USA code 7541 for more information.