Grounded O2 sensors possible bad ECM

I had posted this in the Electrical section, I tired to delete from there and add to here but couldn't figure out how. I hope this is ok. Getting desperate for any advice. Thanks!!

My son bought a 2009 Jeep Wrangler JK a few years ago (long story but got totally scammed). Failed emissions in CT and can't get the engine light off so they will not retest. So, now it can't be registered without passing emissions. I took it to a mechanic and the dealership had grounded all the O2 sensors to the wiring harness. He also pointed out a ground wire under the hood that should not be there. At this point, I just want to get the engine light off and hopefully pass emissions so I can register and be good for a few more years. Also, the mechanic said there is really nothing else they can do to troubleshoot the issue because of all the "grounding" to bypass the original problem. Any suggestions or is this just a big expensive lawn ornament now?

 

Too bad about your Jeep experience but I’d focus on undoing any “grounding of the O2 sensors” or whatever damage was done to the wiring harness. Id suggest picking up the OEM repair manual with all the electrical wiring diagrams to help determine any alterations or changes from the previous work. Troubleshooting electrical components compounded by questionable previous work can be difficult and expensive to solve so any DIY work you could perform will be a plus.

 

Thank you for the response. Great idea! I didn't even think of that. Any recommended publishers for the manual? Haynes and Chilton come up a lot in my search. Thanks again!