Changed BCM and now "limp mode"

Hi, I recently replaced a BCM in my 96 Caravan 3.3. The gas gauge didn't work with the replacement so I took it out and put back the old one. Problem is now, the panel doesn't light up when the headlights are turned on and the transmission is in limp mode. Does anyone have any suggestions on how to fix my problem?

Hope you did all disconnecting/reconnecting with the neg battery cable disconnected otherwise you can easily damage fragile microprocessors in the module.

Are you seeing the Service Engine Soon light? It indicates you have a fault code stored. You can cycle the key from off to on 3 times then with the key at "on/run" count the flashes of the SES light. That's your code. If that doesn't work head to AutoZone or most parts stores. They will scan it and read the code for free.

You could remove the BCM again and check for any damaged pins or shake the wire harness and see if anything comes alive.

Yeah, I actually gave up and sold the van. I've still got my 05 GC to get me around. Thank you for the help RIP.

Well hey, that's one way to "fix" it.