Volvo L180E Electrical Problem

I have a 2007 Volvo L180E wheel loader. I had to do some welding on the bucket so i unhooked the engine ecu and the batterys. I did my welding and tried to start the loader and all it will do is crank but not fire. I am getting a bunch of ramdom codes on the display in the cab. Our volvo Dealer came out and is saying that there is a bad injector causing this and that there is no way the ecu is bad. When you turn the key on everything is fine, but as soon as you start cranking it, it starts showing all the codes. Also every time you try to start it there with be a whole different set of codes. Almost everythime it throws a code for all 6 injectors. I have cleaned and checked all the connections on everything with no luck. At one point the loader started a couple times but sounded very bad, but not like a injector issue. I have been around truck engine for a long time and have never seen an injector go bad and cause this to happen. I am thinking the engine ecu is bad. Any help would be greatly appreciated

Thanks

You would have to list all of the error codes with the FMI's to really tell what is going on. But most likely when you removed the connectors to the ECU you damaged some wires and the harness is at fault.
One thing to look ath the conectors and the ECU and make sure all terminals and pins are straight and not damaged.

Tell me if you are getting codes for can bus faults, if so, you probably burnt the harness