So… we ran through our full suite of tests to determine the cause — thinking perhaps that it was the brake lamp switch (which is a little plunger-type switch attached to the brake pedal.) Then we discovered something odd: when we would turn the parking lights and headlights on, the brake lights would come on and the van would be able to shift again.
So we continued running down the problem and discovered that it was a simple fix: the brake light bulbs have two filaments in each bulb — one for the parking lights and one for the brake lights. Like any other light bulb, they tend to get hot when on for long periods of time. Turns out all the stop-and-go driving in this van actually caused the two filaments to melt together, completing the circuit when the parking lights were on and shorting out the brake light circuit. Total repair: two bulbs and a fuse.
We have some of the brightest minds in the industry working to solve your car problems. What seems like a major problem could be something simple.