Starter engages and turns motor strongly, and battery is recently good, and connections are clean. However, there is no electrical power to ANYTHING. No doors, seats, locks, dash, lights, etc. since engine wont fire, I suspect ignition is likewise powerless. There is indeed power at the IPM with no blown fuses or links... problem was instant with no precursory problems.

So two things I can think of:
1) bad ignition switch. I think unlikely since starter engages, but testable for other poles...
2) BCM, PCM, ECM. Also I think unlikely since any one of these should not disrupt power to all systems...

is there some master fusible link from the battery? I cant find one, and electrical diagrams show all in the IPM which look good. Tried disconnecting and reconnecting battery, and curiously, some relays keep clacking away until I turn on the key: the APS relay, and something inside the throttle body. I assume these are accelerator position sensor system items and not relevevant to power. However, it indicates that power is momentarily being applied and disconnected and then repeating endlessly, and that key on is indeed functioning.

Any thoughts as to root cause? How else might I test it? A complete electrical schematic would be helpful.

 

where on the planet are you located? so we know of which market area the van is made for.
Did you check and clean the ground cable connection points to the body and eng/trans assembly? Since starter works , possibly a bad body ground wire/connection not completing the electrical circuit for the rest of things?

 

 

Rebel59 made the call. Started check for voltages with the ignition switched on, unplugging fuses and links, to discover only 7V on the ignition circuit to ground battery terminal. So I started digging at the smaller ground wires going to body, and found the disconnect. Can’t understand how I lost the nut, but there it was. I suppose the cable was touching well enough all this time, but finally fell off.

good sleuthing!

 

glad to have helped, Sometimes it is better to check common things than start digging at and replacing EXPENSIVE components. NEVER rule out basic checks without a good "look see"!