I pulled the an old wiring harness from my 2010 Volvo s40 ordered a new one on eBay everything was hooked up properly and in right place but now it won’t even turn over. What am I doing wrong? No codes are coming up either when I plug a reader into it. Anybody tell me where to at least start? Wipers and lights come on but won’t turn over?

 

did you check fuses? Any other symptoms? there's a few things in play here that may need a deeper dive with a wiring diagram and a probe. If you burnt a harness, its possible you could have damaged other components like the CEM (the central electronics module has relays inside of it). You may want to check out Xemodex to see if they can do any diagnostics on your CEM.