I recently swapped the computer in my truck for one that matches the hardware and service numbers match but I can't get it to program can anybody help me

 

What specifically is the issue? What do you mean by "can't get it to program"? What is it?

 

If it's what I think you are talking about, you need a computer that is programmed for whatever years you are licensed to tune. If you have HP Tuners. If it's the wrong year you will not be allowed to do anything

 

I ordered a ECU off eBay for my truck which is a 2003 Chevy Silverado LS and is supposed to be compatible but when I install it.... Doesn't work all the numbers match how do I get it to work truck won't start with it installed

 

You have to send it or take it to a tuner that can disable the VATS security system and confirm that it's programmed to your engine/transmission.

Even if the numbers outside the computer match, you don't know for sure if it came from a 4.3/4L60e, 4.8/4L60e, 5.3/4L60e, 6.0/4L60e, 6.0/4L80e, etc.

Other things the tuner can program is things like your truck's VIN and gear ratios.