2011 Electrical fault gremlins

[Midland]

Just went through a bunch of electrical issues on a Prostar. Make sure the big red wire from the 100 amp fuse area is in good condition and tight on both ends. International says the test for good ground on the BCM is to open the door and see of the dome lights come on. Lights on = good ground according to their manual. My experience is that it (BCM) is grounded even when unbolted from the truck body, so that means it would ground through various plugs. Find those grounds and make sure they are tight and not subject to water penetration. There are a lot of interior cab grounds behind/under the dash pretty much straight ahead from the headlight switch. More on the outside of the firewall at the same location. I don't recall what each 100 amp fuse (located on the outside firewall by the grounds) go to, but when one of mine was bad either the horn blew all the time or the wipers ran as soon as the key way on and the truck brake lights were always on. Those fuses look OK even with they blow, though I would suspect from your description that yours are OK but would still check the connections. There have been some cases of water leaking in on the BCM--my truck occasionally leaks from somewhere near where the visor bolts on which can't be good for a lot of things including the BCM. As I understand it, the BCM drives the IC (instrument cluster) and if you are loosing all your gauges including air pressure that points to a BCM issue and/or wiring between the BCM and IC. If you are only losing engine/speed information that could also point to data link from the engine which goes through the BCM before it goes to the IC. Sort of a ramble here, but work on all those wires right inside and outside the firewall directly above and ahead of the BCM.