X2 on the FICM send it to Ed

Also check Alternator output

You said that you had 12Vdc and it went down to 10VDC on FICM Lodgic power

It should start Low say at 10VDC right after crank IMO and then slowly rise untill GP turn off and then you should hit 14.3VDC as the alternator charges

The way you put it looks like the Alternator has Taken out the FICM start 12VDC and Lose Volts as it runs to 10VDC

And welcome to FTE