Can someone tell me what this is? It turned on and made a buzzing noise when I turned my truck on and now it won’t turn off even after I turned the truck off. I had to unhook the battery

 

ABS module. Shouldn't be powered when the truck isn't running.... (ignition on, at any rate.) and it should only buzz for a few short seconds, and stop.

 

so I’m guessing my ABS is faulty now and I have to replace it?

 

Not necessarily. There may be something activating it that is stuck. Fix the cause, not the symptom.

 

Possibly but try to make sure that's the problem. IIRC you can't get these modules anymore and it's either the junkyard or a rebuild service. Both of which are hit and miss.

Fuse 11 (40A) in the PDC is permanent power to the ABS module. There is also a switched power connection but for now let's assume that it turns on/off as designed. So pull fuse 11 and see if the noise goes away. Then, disconnect the connectors and look for corrosion or heat marks etc.. A couple of years ago I had a nagging circuit error that was remedied with some contact cleaner and exercising the ABS on a dirt road.