Service Engine soon ligh

All four go out at the same time is a bunch of crap.

Just replace the bad one, but take it to a local shop that won't rip you off like that dealership. If you have them change out the sensor, ask for the old and then test it your self using a propane torch.

Next time you get a check engine light, take it to AutoZone and they can read the codes for free. You should probably take it there anyway and they could probably sell you the part too.

Rich

I'd just replace the faulty one, and at that, you can buy after market ones that will work fine. On this NG, Bosch seems to have a bad name, but there are other supplies of O2 sensors. The error code the dealer read should tell you exactly which oxygen sensor has failed.

Isn't a 2002 vehicle still under warranty??

If it is, then have them replace all four, after all it's thier recommendation!!!

In the U.S., newer cars (including 2002 model years) are covered under federal law through the Federal Emission Control System Warranty. Your car manual should have info on this. For 2002, I think the warranty was

5 years or 50,000 miles and covered the catalytic converter and powertrain/emission control modules.

So yeah, have the mechanic change all four O2 sensors if he feels it's necessary... on his dime! :)

just replace the bad sensor, they should last at least 90,000 miles. Bosch has a bad name on here, but I've never had a problem with them and I have no problems using them either.