Motopilot

Okay, I bought a 2000 Trans Am stone stock. It runs great, the only problem with it is the drivers side post cat Oxygen sensor throwing a code, and therefore is keeping me from passing emissions.
After testing, it threw a po 140 No activity B1 S2, so I replaced the corresponding sensor. Cleared codes, and drove until MIL lit up. Got back under the car, and realized the colored wires were in the incorrect places in the male connector(attached to the wiring harness). I put the wires in correct places, and re-tried. Threw code again. So, thinking I may have damaged the sensor, I swapped with a working one. After driving, it not only threw po140, but also po160 B2 S2 No activity (the one I swapped).

I guess my question would be, what should I do now? Is it a wiring harness issue, or pcm? Did I damage the computer by plugging wrong colors into sensor?

Also, don't know if this is the right place to post this thread. I am new, and it is a technical question so I assumed. Thanks, Motopilot

Chris25

iTrader: (1)

Are you sure the cat isnt clogged on that side causing the sensor to read a fault.

Motopilot

Could be. Do you think it would throw a no activity code for that? Stupid question: How would I be able to tell if its clogged?

RevGTO

iTrader: (12)

You would probably have a cat inefficiency code if that was the problem. I take it that you have stock manifolds and cats, right?

Motopilot

Thats what I thought, would be a po420 or something like it. Yes, the exhaust is completely stock.

Mercier

iTrader: (15)

1) $1 piece of rebar for cat "adjustment" (poke, shake, repeat, wear a dust mask)
2) O2 simulators(rear only)

$50 and a few hours of work and you wont have the problem again.

Not sure if the inspectors in your state are smart enough to look for such a thing but in my state they definitely are not. Don't know if they would even care.

RevGTO

iTrader: (12)

^Following your suggestion would leave him with non-functioning cats but wouldn't do anything to solve the O2 sensor codes he is throwing.

Mercier

iTrader: (15)

How is that? Do the aft simulators not work on F-body cars?

Motopilot

Agreed, I'm thinking at this point, the problem isn't bad Cats, or Sensors. Haven't been able to get a long enough node for a volt meter yet, but my best guess is that there is a wiring issue on the harness somewhere on that side. I think this might also explain why the (new replaced) B1S2 o2 got fried. If anyone has any type of procedure on how to check if the wires to the sensor are bad I would greatly appreciate it.

Fry_

You could unplug the PCM and the O2 sensor put a jumper wire between the wires at the sensor plug and check for continuity with a DVM at the PCM connector.

Motopilot

Fixed the problem. Turns out the wires were plugged into the connector wrong. Switched them around by using the working side as a baseline, and now I have no code. Still have an unrelated intermittent starting issue, but at least it passed emissions. Thanks for the help.

Just in case someone finds this thread with the same issue, the CORRECT wiring sequence from harness to sensor should be:



Purple-Purple Purple= Signal Wire 1volt ish

Brown-Pink Pink= Heater 12v ish

Brown-Black Black= Ground None if correct

Tan-Tan Tan= Heater 4.12v

blackbird8702

my 2002 firebird formula is running full headers and a cat-less borla exhaust with an electric cut out. what o2 sensor would be best to work with this?, and should i use a tuner/get it tuned after replacing sensors?, or just replace sensors and clear codes? any advice would be greatly appreciated. thank you

RPM WS6

iTrader: (3)

Just to be clear for future readers of this thread, there is no code to indicate a clogged cat. The P0420/P0430 codes DO NOT directly indicate this at all. In fact, if you remove the cats entirely and don't re-tune the PCM (or install O2 sims), you will eventually trip a P0420/P0430 as there will be no difference in O2 sensor readings from pre to post cat.

There seems to be some internet misunderstanding about the nature of these "catalyst below efficiency threshold" codes. The PCM compares pre and post cat O2 sensor readings as A/F ratios are adjusted, and if the post cat sensor too closely follows the pre cat sensor readings, then it's determined that oxygen storage capacity of the cat is below acceptable levels thus representing tail pipe emissions that don't meet EPA standards.

Yes, it's possible to get the P0420/P0430 due to a damaged cat that also happens to be clogged, but the code doesn't actually indicate a clog nor any change at all to exhaust *flow*, nor is there any other code that directly indicates a clog or change in flow.

P0420/P0430 will present any time that a cat is removed, or when substrate coatings have worn off making the cat a useless pass-thru (common issue for '00-'02 F-body LS1s), or if the substrate has been damaged in such a way that reduces its ability to "scrub" the exhaust to acceptable levels.