[jtjohnston]

Actually, a few days later, I have found my own answer.
The harness clip I found on the rear pillar was the right one.

Yellow - left signal
green - right signal
white - gound
brown - tail lights
It would appear that my test light was not working.

To save money buying the very expensive harness, or even a used harness piece, I made a very nice homemade connection to fit in the female clip.

All I did was take my four pin wire,
strip off a centimetre of each of the four wires,
twist the copper wire until it was stiff,
apply solder to the bare tips, (when cold each end becomes stiff),
nip off each end just long enough to fit (push) into the existing female harness.

The colour-codes match up.

I should use hot glue or electric tape to seal it off, but I will keep the van for a year or so; therefore, a professional job is not necessary. If the van was new, I would go buy a male clip to fit into the exisiting female harness. All the same, my homemade fix is very safe and cheaper. I essentially created my own male tips and inserted them into the existing harness.

The main thing is that the female harness connector existing in the rear driver's side column (of rear tailights) works. My tester light did not. Keys do not need to be on. And I did not have to hack up the wires and solder into the existing harness.

All you have to do is match up the existing wires, which match standard colour-codes:

Yellow - left signal
green - right signal
white - gound
brown - tail lights