The tilt function of the steering wheel on the 2014 ML350 Bluetec stopped functioning. The local Mercedes dealer's service advisor stonewalled me by insisting that it will require a 'diagnosis' and that will cost me A$250 plus 10%GST, excluding the repair. This is an outrage!

Symptoms: When pressing up or down on the knobbly steering wheel adjustment lever, electric sound can be heard but the steering wheel don't tilt. Telescopic function works just fine. This occurs after the steering wheel tilted to the upper limit and became jammed.
Cause: There is a small motor under the dash that turns the tilt mechanism. The motor connects to a spring 'bar' that turns a nut. It is this nut that seized up in my car, perhaps because the motor over-rotated it as the steering wheel is wound upwards.

Possible solutions suggested by other forum posts that DIDN'T work for me:
1. Replace a Plastic dogbone part'. I don't think this is applicable for this model.
2. Pull down or bang the steering wheel to shock it into functioning again.

This is my Fix for a RHD vehicles (UK, Ireland, Aus, NZ, India subcontinent, Malaysia, Singapore, Japan, HK, and most Commonwealth countries). The screw positions may be different for LHD vehicles:
Tools required: T20, Philip#2, 13mm Open End Spanner, Flash light.
Times taken: ~2hrs, for being a noob
Difficulty: Medium. Needs to take things apart. Tight working space, Visibility poor and artificial light is required. Working upside down.
Steps:
1. Remove the 3 screws using T20 screwdriver along the edge of the under dash panel. Also remove the two screws that is holding the plastic OBD housing using T20 screwdriver.
2. Remove the plastic fastener with a Philips#2 screwdriver to release the panel from the air vent.
3. Gently ease the panel down to expose the 3 items still attached: Footwell light, OBD, Bonnet Cable Release. The panel is held on the side and back with plastic tongues that holds onto slots, so it is relatively easy to pull it downwards.
4. Detach the wiring to the footwell light by detaching the wiring harness. There is a plastic clip that need to be pressed to release, the wiring harness is then slide sidewards to detach. No tools required.
5. Detach the OBD from the panel by sliding the retaining clip sideway (L & R horizontally) and push the electric connector out from underneath, via the face of the OBD port.
6. Ideally, the bonnet cable release should also be detached but I cannot work out how to do this, so I left it. This means the panel is dangling, so work carefully.
7. Now is the time to look around and orientate yourself by looking up. Check the operation of the telescopic steering wheel adjustment.
8. Also test the operation of the tilt adjustment. The motor (towards the front of the car) should continue to twist the spring 'bar' but the steering wheel does not tilt.
9.Towards the steering wheel of the spring 'bar' (towards the back of the car), there should be a nut. In my case, this nut was stuck/seized. A very gentle wiggle (less than 1/32 of a turn) using a 13mm open end spanner immediately un-seized the nut and the steering wheel now tilt flawlessly. Check the operation of the tilt function again before re-assembly. Space is tight so work carefully. UPDATE(01MAR2024): Sometimes, one needs to grab the solid part of the spring bar near the nut with a plier and give it a wiggle to un-seize it, if wiggling the nut didn’t do the job.
10. Reassembly is the reverse of the disassembly of the under dash panel. Take care to line up the screw holes and making sure the wires are not pinched. Also check that the bonnet cable release still works. I recommend disabling the Easy Entry/Exit feature.
11. There are YouTube video on this. Total repair time is 30-60mins