We had this problem with a COMM (AN/MRC-145A )truck. One of our Marines found a burnt out wire and no one knew what it is. After some research i found this.
"On the M1097R1's my unit recieved from Red River Depot (recap program), there is a wire with a diode in the middle (looks like a small fuse link) and has a yellow tag on it. It plugs into the 54C wire by the fuel injector pump and grounds to the intake manifold bolt. This same part is also plugged into the 25B wire and then goes to ground, by the horn. Russell from Red River says that it is an upgrade that reduces feedback to the PCB. You won't find it in any TM.
The NSN is 5961-01-180-5634
We recieved these vehicles directly from the RECAP program with a burnt out semiconductor already. No telling how quick these will need to be replaced.. "
I'm still waiting for this part to come in but I'll updated when we get it.