So if you recall I bought this 05 ML500 in kind of a shady deal, $400
for the vehicle, $275 to spring it from jail where it had been towed.
It had a "Start Error" which would not allow it to start. I spent a lot
of time digging into it with the majick computer, and managed to clear
the Start Error message on the dash. Was not apparently the keys and
code chips as those all checked out OK, the DAS (Drive Authorization
System, a little loop antenna around the key switch that reads the chip
in the keys) appeared to be happy. I had pulled a DAS loop and module
from a junker for cheap, they are like $175 new, did not need to use it.
Still would not start, after doing some research it was suggested that
the starter power K11 relay in the fuse box under the hood was either
bad or it was not getting power to make it work. Swapped out relays
(there are a bunch that are the same), still no workies. Turns out
after doing some electrical diagnosis I discovered I could jumper the
relay contacts to get the engine to turn over and start with the key in
Run position 2 (all dash lights come on. (YAY!!!!). I put a momentary
contact switch on the jumper wires so I could lift the hood and turn
over the engine to start. (I tried to run it into the cabin but
couldn't find a convenient hole).
So that suggested that an electrical switch behind the key lock switch,
that the key lock actually actuates to start the car, was bad in the
start position 3 -- positions 1 and 2 worked and I could start and drive
the vehicle in position 2. There is a way to test the switch and
wires right there at the switch (pink wire I think, marked #15?) but it
is tight in there so I didn't bother with that aspect, in any case that
wire is what goes to the relay activator contacts (these are the
contacts in back of the relay slot that are along the axis of the car,
the actual starter actuator contacts are the front ones that are
transverse) and I was getting no power to activate the relay.
Common issue on these vehicles apparently, can make you crazy, a new
part is like $25 so I ordered one the other day.
There are 3 covers to take off around the back of the steering wheel and
the various arms behind it. There are 3 Torx T25 screws on the bottom
one, some plastic tabs on the top one, and some tabs and metal snap
connectors on the right panel. They mostly pop out with release of the
tabs and a bit of gyration and having the wheel tilt up or down.
The electrical switch is at 90deg to the key switch in a round housing.
They are (fairly) easy to pull once you get the covers off. Small hands
would help but I managed to get the connector off (there are locking
tabs with little arms you can squeeze with your fingers, although I used
a screwdriver to push the front lock tab you can see and managed to
squeeze the back one and the connector popped right off. Note that
there are some tabs on the top of the copnnector that slide into the
back of the lock and in the housing so it will only orient one way,
pretty much with the tabs on the top at 12 oclock if you could look from
the back.
The actual switch is further inside the round housing, and there are
also 2 locking tabs that hold it in. You can feel inside the round
housing and get the tabs released, although again you can use a
screwdriver on the one if front. I could not get a good grip on it to
pull it out so got a small pair of pliers to grab a contact tab and pull
it right out.
There is a small tab on the back of the key switch that turns the
ignition switch, it is like 1/4" wide it looks like, you can see on the
new one how it will fit over the key switch tab. The old one was
clearly chewed up a bit and it was hard to turn with a screwdriver even
if the slot was OK (which it wasn't) so that was the problem, the switch
wore out or bound up and would not turn to position 3 to start the engine.
The new one slid in OK once I got the tabs oriented to the slot in the
housing, as with the connector, although I did have to put the key in a
move it a bit before the new switch would slide over it but that was
easy enough.
Buttoned everything back up, took out my jumper switch, popped the relay
back in, and JOY!!!! Engine started right up. YAY ME!!!! I did notice
too that the key turned more easily so the switch was definitely
buggered from that indication as well.
This time it took like an hour, next time would be like 20min.
I"m going to put this in Benzworld with pics of all the bits involved.
https://www.benzworld.org/threads/w163-ml500-ignition-switch-no-start-fixed.3060413/
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--FT
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