Most catalytic converters fail due to engine related problems. Replacing the catalytic converter without fixing the cause of the failure may lead to another ruined converter.
Common causes of failure:
Most catalytic converter failures are caused by conditions or events other than converter malfunction:
Installing a new converter
A catalytic converter has three main components:
In addition to these components, many converters will have O2 sensor ports and air tubes.
How a catalytic converter works
As exhaust gases pass into the converter and through the substrate, the washcoat creates chemical reactions that lower the level of emissions emitted from the tailpipe.
A catalytic converter needs two factors to operate properly: sufficient operating temperature (the “light off” temperature) and a steady stream of feed gas. Once the “light off” temperature is reached the catalytic conversions occur: 1) oxides of nitrogen (NOx) are reduced into nitrogen and carbon dioxide, and 2) hydrocarbons (HC) and carbon monoxide (CO) are oxidized to create water vapor.
Converters typically start to work at around 550ºF. The majority of the purification takes place once the converter reaches at least 750ºF.
Diagnosing catalytic converter failures
When a converter malfunctions, it can be due to an engine performance issue or an issue with any of the components in the fuel, engine, and exhaust systems. Typical issues include faulty O2 sensors, incorrect air/fuel ratio, unburned fuel entering the unit, chemical additives in the fuel, malfunctioning sensors, ECM failure, and road damage. One or more of these conditions can trigger a change in emissions at the converter, causing the ECM to record a code that indicates “Catalyst Efficiency Below Threshold”.
If a catalytic converter has failed, it is up to the technician to thoroughly diagnose the problem to find out what caused the failure. If this is not done, it will eventually lead to failure of the new converter.
Codes PO420 and PO430 indicate that the “catalyst system efficiency is below threshold bank 1 or 2. In other words, the vehicle’s oxygen sensors downstream noticed that the converter is not working as efficiently as it should be. However, code PO420 and PO430 can occur for a variety of reasons other than converter failure or malfunction. It is important to properly diagnose and identify any problem or problems before installing a new catalytic converter.
Converter replacement requires ECM reset
When a converter is replaced, the technician will need to perform a drive cycle in order to correctly reset the ECM. Follow the manufacturer guidelines for the correct drive cycle.
Conditions that can lead to a Code PO420 and PO430:
Fuel trim too high
Fuel trim too low
O2 sensor problems
Maintenance / operation problems
Mechanical / electrical issues
Even if you’re not located in California, you may have California emissions-equipped cars come into your shop. Here are some facts that you need to know when dealing with the exhaust systems for California cars that are registered outside of California:
When it comes to vehicle emissions, there are two regulating authorities: U.S. Environmental Protection Agency (EPA) which governs the Federal law throughout the country and the California Air Resources Board (CARB), which governs emission laws in the state of California and 13 additional states that follow CA emissions laws. However, only California applies its stringent regulations to the use of aftermarket replacement converters.So what kind of converter can you use as a replacement in the other 13 states? With so many variables, it may be difficult to know unless you can determine if a vehicle was built to meet federal or CA emissions. Look at the picture below
Both of these systems are listed for a 2000 Nissan Maxima.
However, only the one below fits a CA emissions vehicle. It has three Oxygen sensors and a different configuration.
A common misconception is that a Federal converter can be used on any vehicle not registered in California. However, this only applies to vehicles with Federal systems. If the vehicle has a California system, it must use a converter made for that system. While the converter does not have to legally meet CARB aftermarket emissions standards, it must meet the “mechanical” conditions of the system. This is important because the converter configuration, length and Oxygen sensor locations may be different in the CA car.
Vehicle emissions systems labels
To properly determine whether the vehicle requires a CA or Federal converter, you should check the vehicle’s emissions system label.
Emissions label locations
Common vehicle emissions label locations are: