what could it be ?

messed up wiring harness? I only recently changed my clutch and added an exhaust with an 02 simulator. It was fine until now but when I scan it it pretty much says no error.

 

"Pretty much"????? If you have a CEL, it will have a code.

 

a CEL doesn't come on for no reason. there is a code stored when the CEL comes on. we need the code.

https://www.s2ki.com/forums/index.php?showtopic=378792


also, did your exhaust go up to the header and remove the cat? installing just an exhaust would not require you to use an O2 simulator since your cat would still be intact....