ok so i have a 98 grand 4.0 today i had to weld a hole in exhaust pipe behind cat inorder to remove broken o2 senser no biggy right but after i was done and had new one in i went to start it up and all it does is run for 3sec and dies thing that i have tried are new ecm new body computer and a new dash cluster any help please oha by the way no there is no reading on the dash no volt no check engine light nothing and the power windows dont work now

 

Did you disconnect the battery before welding the exhaust?

 

no

 

You may have fried something then.

 

ha i know but what could it be and how to i find out what

 

U need to check fuses theroly.. Zj has a extreme fuse / relay issue with stock security system.. Is the stereo keepinf memory or the overhead lights working?? Check all tge fuses in the box inside the passenger door

 

AC welding on cars with the battery connected is bad news. On older cars, you can even fry the diode bridge in the alternator. Hopefully, the fuses caught the brunt of it. Check the fuses for anything that is hot at all times, like the PCM memory, radio memory, etc.