P0137 Before or after CAT???

[thats_reality]

hi, have a 1996 3.8L. installed headers and got P0137 code within 1,000 miles. have headers, hi flow cat (about 2 yrs old) and magnaflow catback. just changed the precat O2 and code came back (1996 has 4 sensors, 1 in each manifold, 1 just before cat and 1 just after cat). p0137 refers to bank 1, sensor 2. does anyone know FOR SURE if this is the sensor just before or just after the cat? if its not a faulty sensor then what could cause this code? if the headers could be causing this would adding an o2 sim correct the problem or what? any help is appreciated. thanks

[Richardcoelho]

Re: P0137 Before or after CAT???

i believe it is before the cat,i have the exact same code,alson with po146 bank1 sensor 3 CKT no activity which i believe has to be after the cat,since i dont have a cat i dont have a sensor there anymore so i understand that code but i dont know about the first,it says CIRCUIT LOW VOLTS?

[thats_reality]

Re: P0137 Before or after CAT???

ya, says low voltage, bank 1 sensor 2. was getting the code about every 100 miles. put a brand new sensor in and now i'm getting it about every 10 miles. i am assuming its because the new sensor is reading everything better? no idea really. from what i've read the 2 down stream sensors won't have any effect on performance but will stop me from passing inspection. wondering if a leak at the headers or more likely at the y-pipe would give the p0137? anyone know for sure? seems like the manifold sensors would ses if a leak were at the headers. is it the just before cat or just after cat that ppl have used o2 sims? again, thanks for any help!