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P0140- Bad Cat or Sensor?

SomeDudeAtHome

SomeDudeAtHome

New member
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.
 


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?
 


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.
 
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.
 


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