I have a reminder in my agenda to check PSD fluid as it is often forgotten. Today was the ay. I checked and fluid level was fine. No problem. The GTS has a little peek-hole in the rear left fender and if you remove the cover plate you can see in. You can also reach in. A quick refresh of the fluid is rather easy if you have the right tools, and there is no need to take off the (often brittle) cover inside the fender. So no risk of damaging that one.
You're supposed to bleed the bleed screw on top of the valve, but since there is no air in the system I figured that was not absolutely necessary. You can just bleed over the nipple at the slave cylinder. So that is what I did.

Small hands required :)

  1. First go in with your hand and clean the lid on the reservoir.
  2. Unscrew the lid and leave it hanging on the overfill hose.
  3. Use your finger to take out the little sieve that is on the opening of the reservoir. Now make sure that no dirt enters the reservoir.
  4. I use a large syringe with a 15cm hose on it to suck out brake fluid from the reservoir. Just enough so that you have a little left.
  5. Replenish with fresh fluid all the way to the top. Way more than the max marker. The syringe with a short hose on it is perfect to guide the fluid back in without touching any dirty areas.
  6. Locate the 7mm nipple at the final drive pass side. Undo this a little and put a small hose on the nipple to guide the fluid into a container or a catch bottle.
  7. Use a diag tool (like the PDT999, UDT999, Bosch Hammer) to command the PSD ecu to bleed the system. Small pulses of old fluid come out of the bleeder hose. Watch the reservoir. It must not (!) run empty.
  8. Stop, refill, and do it again. Until you used up about 500cc. That should be more than enough to flush out the old fluid.
  9. Close the nipple, undo the hose, check fluid level, put in sieve, close the lid, clean things again if you spilled, close the peek hole, and do a test drive.