Thread: P0140- Bad Cat or Sensor?

SEL light turned on today and this is the code that it's giving me. The car is a 98 GT with 61K miles one it. There's no serious engine mods and only exhaust work done after the cat. I've done some searching and know this is the code for the rear o2 sensor but what I'm not sure about is the cause. On a car that old with that amount of mileage would you guess it's a worn out sensor or a bad cat? Is there a test I could do that would tell me which one it is? I already have a 2.5" downpipe sitting in the garage and a Reptile tuned PCM that will erase the code so it's not a big deal but I'm just curious. I've been lazy installing those things but looks like I might have to sooner rather than later now. Just have to order a emulator now.

http://www.obd-codes.com/p0140

not a cat, the o2 heater is dead.

Alright so I guess through everything I read I misunderstood what it meant a little bit. Does that mean though that replacing the sensor will solve the problem?

it should. hard part is getting the old one out. they like to rust in there and fight on the way out.

Thanks Scotty. Looks like i'm going to get an emulator and just swap it with the DP this spring/summer

you can just delete it and tune it out. mines long gone.

I actually have a PCM from Reptile with the code tuned out. I'm going to get the simulator just to be safe though being in NY with the state inspections.

run the pcm and forget about the rear o2. it will show ready and thats all that matters for inspection.

pretty sure i got 24 codes deleted or so. i passed inspection.

Alright guess that's what I'll do then. Should I just swap the bad one over then when I switch dp's?

good chance it wont come out at all. not with out a torch maybe. you can have no o2 at all with it tuned out. or put a wide band o2 sensor in the hole.

if you stop by a local garage they have o2 sensor plugs laying around sometimes. they come in new dp's and they tend to save em time to time. one of my local guys has a box of em.

If I put a plug in there could that cause a problem come inspection time if someone notices?

i dont think they count o2 sensors, as long as it shows system "ready" its a go.

That's what I'll do then