Aftermarket catalytic converters can fail specifications

By Doug McAllister

Q. I have a Toyota Camry and I recently had its catalytic converter replaced. The problem is my check engine light came back on two months later. The repair shop is telling me the new converter is bad and they want to put a factory one on instead of another aftermarket (part). There is a huge price difference and I really don't want to pay it. What should I do?

A. I totally understand your frustration and the sticker shock because of the price. We run into this a lot and typically my shop will not install an aftermarket converter on a Toyota; they just don't seem to work.

On some cars these catalytic converters will work fine but there are many makes and models on which we have had bad luck. Even though the factory part is double the price of an aftermarket converter, sometimes it is the only way to go.

The algorithm the computer control module uses has very tight tolerances. For some reason, the aftermarket converter falls out of the specs very easily. It is probably still working - it just won't satisfy the parameter that is set up in the powertrain control module (PCM). You are much better off taking the one-time hit and using the OEM (original equipment manufacturer) part. Hopefully the shop will absorb the labor and you will both be off to bigger and better things.

Thanks for the question and good luck,

• Douglas Automotive is at 417 W. Main St., Barrington; 123 Virginia Road, Crystal Lake; and 416 Northwest Hwy., Fox River Grove. For information, visit douglasautomotive.com. Send questions to underthehood@dailyherald.com.