Dear Car Talk:

Two years ago, my son bought a 2002 Saturn L100 in California. When he tried to re-register it and get a smog test this year, the emissions were good, but the car did not pass the smog test because the station said it had the wrong catalytic converter installed. He went to a DMV appeals hearing, but had no luck. He's already paid the registration fee, which is nonrefundable, and is stumped about what to do. He's tried contacting the car seller, with no luck. What is the most logical, speediest way for him to handle this? He wants to buy a converter (with the valid ID number) online and have it installed.

-- Nadine

If the converter is the only thing keeping him from passing inspection, I think buying a proper converter is his best bet, Nadine. Someone pulled a fast one on him.

You don't say whether it was an individual seller or a used-car dealer of some kind. But my guess is that a previous owner of this car failed a smog test. And rather spend the $500 for a new converter, he or she dumped the car. Cheap.

Whoever bought it turned around and "patched in" an incorrect, cheap, aftermarket or possibly used-car-sourced catalytic converter. Somehow, he or she finagled a smog inspection, and then sold the car to your son at a nice markup and changed his or her phone number.

The seller obviously knew that your son wouldn't discover the problem until his next smog check was due, two years later. And here we are.

So his only real recourse, if he wants to keep the car, is to get a legitimate catalytic converter. And if he still has any information about the seller, particularly if it's a business, he should report it to the California Department of Motor Vehicles. That might not help your son, but perhaps it'll help someone else down the road.