There are many reasons for E150. Please make sure the battery is 100% No shorts to frame.
Most common problem is break in the can-bus wire harness right over the brake brake drum where the harness flexes. This is a grey four wire harness that runs from the plug on the drive motor and goes over the brake drum to the diagnostic plug. This wire is part of the main harness. To verify this, Jack up the truck, remove the top cover and harness clamps. Pull back protective cover and get access to the grey 4 wire harness. There are 2, one is for the motor encoder, grab the other that goes to the diag plug. Put the truck in drive, get it spinning the drive tire. garb the grey harness and pinch, wiggle it at the area where it bends on turns. If the truck codes out, you have a break in the harness. As a rule, it's 30 inches from the drive motor plug. there can be 2 wires broken. black ones usually. You can repair the break and re-route the harness further back where it no longer flexes. Or replace just the can-bus wire, or complete harness. Good luck