P0420 Catalyst System Efficiency Below Threshold (Bank 1)

Hello all,

I have a '95 Eclipse GST with 86k miles and my "check engine" light came on recently. I took it to my local dealership and got back a OBD code of P0420 (Catalyst System Efficiency Below Threshold (Bank 1) ). He recommended replacing the rear O2 sensor --AND-- the converter ($1369).

My questions are: Shouldn't the dealer know if it's just the rear O2 sensor by doing some diagnostic tests-- thus saving me +$1000 dollars? Or would he definately know it's the converter, and if so, why is he suggesting replacing the rear sensor as well? I just want to make sure everything is on the up and up...

Oh, and also: He asked me if I planned on keeping the car for long, and I said not if it keeps costing me this much to run it. Then he said I probably should not get it fixed because it's only going to get worse. You think he's being sincere, or is this just a way to get me from going elsewhere to find a cheaper solution?

Thanks!

  xj220

wow i love guess and check technicians. its either the rear o2 or cat crapped out.. highly unlikeyly both. but yea replacing both will fix your problems.

although he should suggest to u to check the cat first. i didnt know cats were that expensive.

  thongsai

Thanks for your reply.

Yeah, this a-hole dealership has gotten the better of me before, so I'm much more cautious of their "solutions" now. I only take it to them because they're the only Mitsu dealer around for miles.

One time, I took in for service for brakes, and they told me the battery died (without warning)-- wanted to charge me $150 to replace it. I went to Sears, bought a $59 battery and I replaced the damn thing myself at the dealer's lot. During another service they said my headlights were oxidizing and wanted to charge me $540-- PER HEADLIGHT to replace! I ordered them on the Internet for $169 per headlight. So yeah, I doubt the cat really costs much to replace.

Ok, enough venting. Time to find an good, honest tech in the area...

  xj220

You can test an O2 sensor with a propane torch and voltmeter. Pick up the special socket at a parts store or something. How many miles does this thing have?

  PeteC