I was getting this error message on the dash maybe 8 times per week and seemingly becoming more frequent. Almost always when coming to stop at a junction, although not necessarily on any incline.
I had also noticed that occasionally pressing the clutch to start the car was ineffective and so I started routinely using the brake pedal instead and forgot all about it, until I put 2+2 together.
Clutch Pedal Switch
. Occasionally it was not registering that the clutch was pressed and so on coming to a stop I would expect the ECU to be confused about how the car was stationary, in gear, engine running, with clutch "not pressed", hence couldn't decide whether to engage hill hold or not.
Picked up a new clutch switch from eBay (£12) and replaced last weekend to find that both above problems are gone.
To change switch:
Tools: Spanner (battery terminals). Torx screwdriver (airbag bolts), Long-nose pliers.
Time: Less than 1 hour.
NOTE: Changing the switch involves removing the knee airbag which is very simple and safe if done carefully, but do so at your own risk!
1. Disconnect BOTH battery terminals and move cables clear of battery, then wait at least 15 minutes before continuing.
2. Remove the driver's central console side trim - this gives easy access to the top-left airbag bolt. The trim just pulls out and is quite flexible so pretty easy.
3. Remove the four torx bolts securing the corners of the knee airbag unit. It helps if you adjust the steering column right up and out.
4. Before you disconnect the airbag unit, touch the metal car body to ensure you're not holding any static. Squeeze the plug and pull out. Put the airbag unit somewhere safe, out the way, face up.
5. Directly in front of the clutch pedal, you can now see the rear of the clutch switch facing you. It is square, beige and has a small, black 2-pin connector on the back. Disconnect the plug (it has small tab on the side to un-hook)
6. The switch comes out simply by turning anti-clockwise. It's set a little way back so grab it with the long nose pliers and turn. It may help to take pressure off the switch while removing/re-fitting by wedging the clutch down temporarily.
7. Refitting is the exact reverse procedure. When re-fitting the switch, it only goes into the hole one way so check carefully where the locating tabs are before pushing in.