R170 2001 first flashed up the check engine light. So I bought an OBD-II tool which showed error P0720 and P0500.
Then soon thereafter, five warning lights popped up and a new error code P0600.
1. Brake pads worn down
2. Check engine
3. Brake Fluid Low (or handbrake on)
4. BAS malfunction / ESP malfunction
5. ABS malfunction
When these came on, the car switched to limp home mode... 2nd gear, no speedometer.
So after a lot of internet searching, I decided to remove the front wheels and check the front pads. They were at 5mm, which is the depth at which the sensor triggers a warning. I unplugged the brake pad sensor wires and put the wheels back on. I then used my OBD-II to reset the error codes and took it for a test drive. No warning lights, no errors. I stopped by both the best mechanic on the island and the auto electrician who agreed with likely diagnosis, saying how a single minor error can light up the dash like a Christmas tree and toss in limp mode.
As it happens, I am flying to the US in a few days, so will order front & rear pads, sensor wires and brake light switch from Pelican because they have such a helpful web site (and way better prices than down under).
It seems a poor design to drop the car into limp mode when the brakes have 5mm left on them, and the erroneous warnings (like brake fluid low... it was not) almost seem to be designed to drive business at the dealer.
In another posting, someone asked if the R170 would become a classic, collectible. I would say with the electronic systems and the potential extreme costs when something goes wrong (I was lucky), the era of collectibles may be over. The R170 is a fun car and I love the vario roof, but unlike my 1982 G-Wagon, electronics can be a financial nightmare.
Anyway, for the next person to encounter these symptoms, pull your wheels, inspect the pads, and if they are close to 5mm disconnect the sensors. If the problem goes away after resetting the OBD then you know it's just the pads... but be sure to replace them.