Updated April 18, 2025
If you’ve owned a vehicle for a while or driven multiple kinds over the years, you might have heard someone mention catalytic converters at some point.
A catalytic converter helps reduce pollution by changing a vehicle’s exhaust emission.
One of our technicians installed a new one on a Dodge Caravan. The minivan was brought to the shop when the check engine light came on.
When checking the O2 sensors on the computer, he realized the converter wasn’t working properly.
When to replace catalytic converters
Whether a vehicle needs a new converter and indicators of a bad catalytic converter can vary.
Some converters don’t go bad. Others may be replaced if an engine misfire occurs. A misfire shoots raw fuel in the converter, which can’t switch over raw fuel. For a driver, misfires may feel like the car is running rough or struggling to accelerate.
The catalytic converter’s temperature is another potential symptom that it’s going bad. Normally, the catalytic converters we check using a thermal imager are around 400 or 500 degrees. If they’re hotter than that, it means there’s a problem.
In addition to the check engine light coming on, you may notice the smell of raw fumes when a new one is needed. However, the check engine light would be your first indicator.
There are many reasons why a check engine light turns on. If it does, it’s a good idea to bring the vehicle into an auto repair shop soon.
Problems with the catalytic converter would also trigger certain codes, such as catalytic converter efficiency codes (P0420 and P0430) and misfire codes (P0300).
Catalytic converter problems
The converter could be clogged, which was the case with a Lexus RX.
To determine if it’s clogged, we need to see if a misfire is occurring on that bank because it won’t allow exhaust gas to get through. A back pressure test can also be performed to see if it’s out of specification.
For example, if your back pressure is supposed to be less than 1 PSI – meaning you have good flow – and it’s anything north of that it means you have restriction in the catalytic converter.
Other converter problems include becoming worn down where they don’t create enough of a chemical reaction.
These components are built to store oxygen. They can stop doing that, causing them to go below the threshold.
Catalytic converter types
Different types of two-way and three-way converters are available. Years ago, one-way converters were used.
On the Dodge, we installed a two-way catalytic converter, which focuses on oxidizing carbon monoxide and hydrocarbons. Three-way catalytic converters do this and also reduce nitrogen oxides.
The type of converter a vehicle needs depends on the make and model, and how the engine runs.
Some cars can have multiple. Usually, there’s at least one converter for each bank. A lot of vehicles now have a downstream converter that isn’t monitored. It can’t trigger a check engine light unless it becomes clogged.
If it comes time to replace your converter, you’re better off investing in a good catalytic converter rather than a cheap one.
Cheap catalytic converters may not be made up of as much material and don’t normally last very long.
HomeTowne Auto Repair & Tire is an authorized Michelin and BFGoodrich tire dealer located in Woodbridge, Virginia. Automotive repair services are performed on all makes and models, including oil changes, brakes, alignments, inspections, and computer engine diagnostics.