Hello & Welcome,
A fast flash is an indication of one or more of the bulbs being out.
Did you check that ALL of the bulbs is working on each side. Don't forget the side marker lights in the front.
The other main issue that is very common on these vans is that the Rear lights sometimes have problems. If you have replace the bulbs, you know that there is a "circuit board" back there. Sometimes moisture gets in there and causes a partial short circuit. This will often cause the bulb sockets to burn and start to melt. This can cause all kinds of issues.
You also didn't mention which side was flashing fast.
You might also want to compare the two sides with the headlights ON and with them OFF. The side marker lights do have a different pattern when the other lights are ON. This might help to isolate the problem.
I can send you a schematic if that would help. Just let me know if you want it.
Take Care, Greg A.
I don't recall a circuit board in the front lights, just sockets.
Was the socket burned at all?
Here is the schematic.
I seem to recall that if the headlights are ON, the side markers should blink in an "alternate" pattern, instead of at the same time, but I might have that reversed.
Just make sure that each side behaves the same way, on both sides, and in the front and the back. You will have to walk around the van to make sure that happens.
Please let me know if you have more questions.
I have an example of how the front side blinkers should work with the lights ON and OFF. Here is a link to that video. Once there, just click on the text for the Normal Working Blinkers."
OK - You have found the problem, or at least the cause of the fast flash.
When you changed the bulb, did you notice any "burned" areas of the socket?
You will have to take the light assembly out again and test for power and ground at that socket, and any signs of wiring or connector damage.
Do you have a multimeter or test light to do some testing?