Mercedes B-Class Assisted Braking
Problem
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The other day my wife
reported that a dire warning message with lots of orange lamps
suddenly appeared and the steering suddenly had became very heavy.
The message told her to look
in the driver's handbook to read about the problem. I did this
and it explained about the radar warnings and even though I used
to work at Plessey Radar, I wasn't really any the wiser. I turned
on the engine and puzzled over the display, then tried to switch
off the various features, in the hope that if these were switched
off, the car wouldn't tell us there was a problem and sure enough
all the warning lamps went off leaving an orange engine warning
lamp. Fortunately this also went off the next day when we were
heading off on a hundred mile journey. The heavy steering also
gave way to normal. At the start of the return journey the whole
thing repeated so I drove back with heavy steering and I also
found that I couldn't engage cruise control which was really
annoying because of very long stretches of speed restrictions
on the M27.
When we'd got back I again tried
turning off the various features but this time to no avail. This
is one of the three different messages that kept appearing...
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Later I looked on YouTube
and found that our "radar" system was carried out by
a module behind the Mercedes Star. It seems that this Star can
be twisted and pulled off for most models but for our particular
W246 B-Class it needs to be prised off.
Without any specific plan in
mind I tried pulling and twisting the Star but got nowhere. It
was firmly stuck in position. I peered at it and because it was
a bit dark didn't really see anything untoward but just as I
was giving up I noticed a tiny twig wedged in a sector of the
moulding. It was really tiny, but I pulled it out and wondered
if this was the problem. I started the engine and the warning
message didn't appear. The orange engine lamp was still lit but
maybe this will extinguish later as before?
The tiny twig had apparently
disabled the following:
ABS, Cruise Control, Assisted
braking, Auto Start-Stop, Collision Warning, and more importantly
made the steering very heavy. Is all this due to AI?
I can see the reasoning for
the true radar-aided features but surely not ABS and steering?
Why didn't the message at least
say, "First look for an obstruction in the Mercedes Star"
??
The radar feature is useful
except sometimes a bit annoying. In the New Forest we have lots
of road narrowing points to slow traffic. These have hefty wooden
posts either side which our car sees and shrieks at us even though
I'm steering between them.
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Heading off down the road
the next day that dreaded warning message appeared again.. it
seems that after deleting the error reports with my OBD device,
one has to drive about 30 feet for the problem to be re-recognised
by the car.
We perservered with the fault
until we got really fed up with the heavy steering. Why is the
steering affected? It's a deliberate action by the cars electrical
system and surely makes things less safe? I know this because
when clearing one of the multiple errors the steering suddenly
makes an odd noise and feels jelly-like (ie. normal).
I decided to check the fault
codes from all 18 control units displayed on my iCarSoft tester.
This time I read every sub-section and noticed one particular
and interesting fault code. This reported a missing signal from
the right wheel speed sensor. Maybe this is the source of the
multiplicity of problems?
In fact this was specific error
was the last one of my mouse nibbling faults
except then it was the left wheel speed sensor and this time
it's the right. And I do recall very heavy steering remaining
after we'd sorted out countless other gnawed wires.
Bearing in mind that there are
lots of rubbish programmers out there (I'm not saying all programmers
are rubbish, but I'm continually finding too many problems these
days whose source is bad software).
Presumably there's a truth table
dreamed up by the Mercedes-Benz system analysis team to guide
the program writers? Something like... left wheel sensor out
of range do X, right wheel sensor out of range do X, rear wheels
ditto. For X do the following.... trigger a set of messages..
light up the following warning lamps... turn off the following
features.... Anyway, whatever was done converts a simple, straightforward
fault into a confusing mess of indications to the driver, for
which the handbook paragraph referred to by the warning message,
incorrectly and confusingly blames the anti-collision radar.
Someone without an engineering background, on reading the messages
take the suggested "refer to the drivers handbook"
as gospel and ask a garage to fix (or even a DIY fix as I just
looked on Ebay and found no less than 130 second hand radar modules
for sale).
Is the whole scenario intended
to signify something dead serious is amiss and head for your
nearest Mercedes dealer forthwith, where they will ponder a few
days, plug in incredibly sophisticated test gear, and mutter
something about "software updates", "faulty ECU",
"faulty radar", etc and make comforting statements
about putting it right and working with customers to reach a
solution... then write out a bill for thousands of pounds only
to discover the fault reappears after you've set off home.
Oddly, I also noted on Ebay
someone selling a "Radar fix" for the firmware which
presumably does away with the consequential actions.. such as
preventing the disabling of power steering?
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Here's my plan. Having,
several months ago, detached the landing platform for mice residents
there were still the odd areas susceptible to rodent attack.
I'd expected perhaps a radar system wire at first, but having
read that wheel sensor error and noted it was just for the right
wheel, surely the problem was another nibbled tasty wire?
I jacked up the drivers side
and removed the front wheel. I could then see the cable emerging
from the sensor, clipped neatly into the front suspension and
disappearing behind the wheel arch liner. Although hidden I could
feel what seemed to be the end of the cable termination in a
plug and socket but no obvious signs of nibbling so could it
just be a failed sensor or nibbling further along the cable en-route
to its control unit? The sensor is a Hall-effect device which
magnetically monitors rotation of a toothed ring around the front
axle and in some older cars it's not a bad sensor as such but
a badly corroded toothed wheel that messes up the system. But
surely.. as the car has covered only about 20,000 miles the toothed
ring must still be good so would a new sensor fix the fault?
It could even be a bad cable or a corroded plug/socket pins.
I ordered a new sensor. Now,
this is not straightforward as there are lots of different cables
available, where the sensor fixing or the plug or cable length
varies.
Below, I'm assured is the correct
sensor, and indeed it was the correct one. Thanks mainly to the
feature on Amazon and Ebay where one adds a car to ones "garage"
where a check links a chosen intended purchase to your cars bits.
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As the far cable termination
was hidden and refused to budge I had to remove the wheel arch
liner and the cover under the chassis behind the wheel. These
are held in place by a mixture of 2-part clips, self tapping
screws and nuts. Then by lying down under the car I was able
to see and detach an odd-shaped piece of plastic holding two
sockets (the one at the end of the sensor cable plus a second
terminating the brake disk wear indicator cable). Once detached
I could see how to remove the plugs by pushing a thin metal screwdriver
into the housing whilst pulling the plug from the socket. Note
that on my W246 B200D the wheel sensor wires are Blue/Brown and
the wear cable wires are Green/Yellow. Both cables disappear
up into the engine compartment and are loosely covered in a tape.
As I'd inspected the whole area
around the wheel arch and not discovering any evidence for illicit
mouse activity there was no reason not to fit everything back
into place. The sensor fitted nicely and I'd spotted the toothed
wheel was shiny so if the new sensor doesn't fix the problem
it'll probably be mouse nibbling in the engine compartment rather
than under the car.
I used my iCarSoft tester to
clear all the faults with the last being the orange engine lamp...
why was this lit? Can anyone explain the reasoning for warning
of an engine problem or is it merely a ruse for extracting cash
from worried owners? "We need to do a full test of all the
electronic systems on our Mercedes-Benz super diagnostic computer"...
"a bargain offer of £300 pus VAT"... "then
isolate all the faulty components, remove and replace for a mere
£2000 plus VAT".. "Oh.. and then recode the parts
to match your VIN... only £250 plus VAT". Guarantee?
you ask... "We'll guarantee the parts and labour but who
knows if a further fault might show up later"... I wish
I'd bought another 1948 Austin instead.
With no warning lamps and no
messages I ran the car (the Merc not that Austin) up and down
the drive with its jelly-like steering and... no messages appeared
and having completed 20 miles all is still OK... but who knows
if a further fault might show up later...
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Mercedes B-Class Windscreen
Washer Problem
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Not long after I bought
my Mercedes B200D I noticed the windscreen washer was pretty
poor and after a few years was only producing a dribble. In fact
a couple of years ago my MoT failed with "Windscreen Washer
inoperative.. needs filling" or something similar. As a
rear tyre was damaged, this was replaced and the car passed its
test (with an "empty" reservoir). A year later the
MoT guy didn't notice the poor windscreen washer or similarly
decided it just needed topping up so I had no trouble.. that
is unless you really need one's windscreen properly clean. When
we decided to take a bottle of water with us recently on a long
trip I decided I must fix it.
Youtube wasn't much help and I decided to fix it through
investigating the problem myself. In fact,
because mice had ravaged the wiring a few years back I'd
already formed the opinion it was a gnawed-through tube that
was the problem and vaguely imagined fitting heatshrink tubing
over any damage. Under the bonnet I found some of the washer
tubes which actually looked OK and pretty tough and I'd already
looked for evidence of water leaks or drips under the car and
found nothing. I'd also completely filled the water reservor
and tried the washer button. In fact by now even the dribble
had gone and I could hear the washer motor whining away to no
avail. The rear washer had also completely failed as well I should
mention.
So, with no real alternative,
I jacked up the car and removed the nearside front wheel. I then
noticed a detachable panel roughly where I imagined the washer
pump was located so removed this hoping to see enough to make
repairs but promptly dropped it behind the wheel arch cover leaving
me little option but to remove the whole cover (something I'd
already planned to do anyway).
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Above, with the wheel
arch cover removed, you can see the windscreen washer reservoir
(that large black plastic thing). Those water stains are from
over-filling before I'd started. The pump is clipped into the
side of the container and has two black plastic tubes connected.
Also, on the left of the pump, is the fitting for detecting the
reservoir is empty and on the top of the pump is its two-wire
power plug.
I unclipped that nearside tube
by slipping its black plastic clip upwards and tried the washer
to see if water was ejected. No water dribbled out and worryingly
the pump wouldn't come on. In fact the wipers wouldn't work either
and I was then concerned I'd disturbed and broken another mouse-gnawed
wire so rummaged under the bonnet trying to duplicate my initial
pulling and prodding of tubes and wiring then tried the wipers
again. Still no response and then I suddenly realised the bonnet
being open might be the reason for disabling the wipers. Sure
enough, closing the bonnet brought the wipers back to life and
surprisingly no water was emerging from the pump from the hole
from where I'd detached the tube.
Was the pump blocked up so I
decided to remove and test it? Maybe the frenzied whining wasn't
indicative of a working pump.. maybe something had bunged up
or come adrift inside? Despite pulling and levering it the pump
remained loosely fixed in place although I could lift it just
enough to pull it out from the reservoir output hole.
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I realised something quite
odd though.. despite sliding the pump upwards and clear of the
reservoir, no water emerged ..... not even a single drip. Maybe
there was a rubber valve in place which only allowed water to
be pumped out once the pump was plugged in? I resolved to remove
the pump and I realised I had no option but to just pull it until
something gave way. I detached the power lead by levering under
the lower edge of its plug and lifted the pump to its highest
position free from the reservoir output hole and pulled very
hard on the pump body. There was a loud "pop" and the
clip around the pump body detached itself from a mating hole
in the reservoir and the pump was freed albeit with the leftmost
tube still attached. In fact the clip on this tube was different
and looked fairly secure and immovable so I left it. At this
point I'd assumed the nearside tube I'd removed was for the rear
washer and the other was for the front. This turned out to be
wrong and almost certainly it was the way air could get in to
avoid producing a vaccuum.
I filled a container with water
and made sure the pump input tube at the bottom was below the
surface and got my wife to start the car and press the washer
button whilst I watched the hole from which I'd removed the nearside
tube. No water emerged so I shouted to stop and try again. The
pump whined away and again no water emerged so I shouted to stop
again. The pump clearly wasn't pumping.. but no .. in fact the
windscreen was being drenched in water.. twice, but I hadn't
heard the shout of glee above the engine noise and pump whining...
So.. the pump was fine and I
turned my attention to the hole in the bottom of the reservoir.
There was a rubber thing with a hole in the centre. I decided
to investigate (I'd assumed it was a valve) so pulled it out
which was accompanied by a vertical jet of water. I put my finger
over the hole in the reservoir and peered at the rubber valve
fitting. It was coated in black gunge. I rubbed some off and
noticed some really tiny holes. So, it wasn't a valve but merely
a filter. I wondered about the contents of the reservor and decided
it would be best if I just let it empty and scour any gunge left
inside so removed my finger and let it finish emptying.
I examined the filter and found
its loads of microscopic holes were blocked so carefully cleaned
the thing in running water until all the holes in the base and
slots in the sides were completely clean.
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Apologies for the blurred
image on the left but you can see the number and size of the
holes compared with a published picture of a replacement on the
right showing larger less-blockable holes.
Is this perhaps an example of
a design problem? Too many owners filling the reservoir with
none-to-clean water or from a garden hosepipe with contaminants
from degraded material leading to complaints?
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To be safe I extracted
all the water from the bottom of the reservoir with a sucker
in case it was mucky. It wasn't and after fitting the cleaned
filter and re-fitting the pump I tried the washer. The pump whined
very loudly and nothing happened except for a warning on the
screen "Refill windscreen washer" ... oops I'd forgotten
to fill the reservoir so carefully added a bucketful of clean
water with a spot of Fairy liquid and on a second push of the
button (with the bonnet closed of course) the windscreen was
completely drenched from the three jets. Now to fit the wheel
arch cover (below). |
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Refitting the cover is
a really messy job whilst lying on a gravel drive with minimal
clearance under the car and, after pushing and pulling with limited
luck, I couldn't fit the last few screws so gave up (the other
16 screws should be enough). The wheel was also difficult to
fit. Some are easy but this wasn't... probably because I hadn't
bothered to turn the steering back from full left lock and the
wheel was exceedingly heavy and awkward to grip.
Hopefully this story will be
discoverable and be of use to other Mercedes owners who perhaps
will be blaming the pump or contemplated getting a garage to
diagnose and remedy the fault? Material and parts costs zero,
labour priceless!
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