I had a no crank issue on the truck and sent it to the dealer, misplaced a relay and fried the fusebox, replaced the fusebox and now the truck wont crank,

error codes I got were the following
p2176 perform throttle adaptation
p0607 Voltage supply of component Motor electronics / Battery voltage too low ADC
p2505 voltage at relay 87 too low.

the dealer is saying I need a new ECU. is there something else to test? maybe a blown fuse inside the front sam or sam distribution box? all fuses and relays checked. they are all in working order. I would like to see if there are more tests to run before pulling the trigger and buy or repair the ecu.
thank you.

confirm battery state is good, erase errors, try again. if still same result- check power to fusebox. check ground fusable links. if still no go, it could be the ecu

battery is good, codes were tried to be deleted and nothing. red cable that bolts to the fusebox has solid 12 volt. all fuses are good.

the guy from the shop told me that he ran a test where he basically checked 2 wires that come with 12 volt to the ECU and the ECU does not supply voltage to the circuit.

Isn't this the X164 forum?

??? Got 2 trucks the gl and the ml

Sorry if I missed something but all I see in your ID space is "2009 ML63 AMG". My comment is based on that because I didn't look any further.

Try replacing the voltage regulator of your alternator. This bad electronics of Chrysler/Mercedes has this issue giving codes that do not correspond to the real problem.
If you do not replace the alternator regulator, someday the ECU your car is going fist to enter in emergency mode not allowing it to get up from 2000rpm and in a few days it is not going to start anymore, in this case, you will need a new ECU.
I hope I could help,
Sergio