CAN Network issue.

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New Member
Jun 7, 2019
W639 vito Sport-W208 CLK Sport-W221 AMG S -Class-W202 C180 EST.
Evening Gents,
I have a CLK320 A208 1998/99 with some some daft issues that I cant overcome that are CAN related.
Not owned car long and bought with ABS/ASR/BAS lights on and took a chance on it being the normal brake light switch as the cruise control also didn't work. Well that did work and i managed to clear the old codes using the Polish MaxiECU software. So now all the lights went out and came back on as rear wheel speed sensor was open circuit.Monster mission latter taking the rear bulk head/firewall 30 bolt plate off job done.
Car drives well.Brakes well.ABS works well. Traction control works well.But the problems are strange.
1) You can take it out of park "without the key in". Steering wheel locks electronically as you pull the key out. Lock out solenoid has voltage but no earth (blue/white). Give it an earth and it clicks.
Car Starts in P and R and all gears past drive are there.
2) Rear windows dont work on switches but do if you open the soft top roof. Or lock the car holding the key fob down.
3)Mirrors don't adjust on consul. But do fold back on a different switch. Mirrors don't adjust in reverse but do activate the parking sensors.Indicating selector knows were it is.Gears that are electronic as in 1,2,3 are all there indicating selector ok.
4) Radio blank dead as a DODO. Pined out rear plugs and constant live and switch live all there.
Polish software read codes of B1058 unkown? and C1025 Can to ABS and nothing else.
1 Month latter and 20 emails to Poland I gave up and bought a C3 Star. That still says the same thing in a much more complicated way.
Replaced: Brake switch x 2. Gear selector.ABS Pump and ECU. Sam x 2 plus both fuse boxs in engine bay.
BAS module under servo. Mirrors,rear window module switch assemble.Alarm Siren with built in battery.
I Dont mind spending money as these parts/spares are cheap as chips now and if you can find a low mileage rust free car with history.....I did. None of these parts are Coded either which is a bonus.
Researched till I was blind how this CAN B system works and all I can make out its like old xmas tree lights (once one bulb blows they all go down but you havent a clue which one.). The X30/7 conector in the left sill panel has a row of brown/black,red wires all connected to two buz bars. Can H and Can L and for the life of me i cant understand why CAN L has a higher voltage then Can H. Neither of these rails ever reach the stated voltage of 11-12 volts during there waky waky time.One is around 4.5 volts that drops a volt but moving a seat or window. 1.8 volts on the other rail. How can that operate anything apart from a clock.
I have pulled these pairs out one at time and re-scanned to see if i can isolate the issue but no joy.
These wires then go into what I consider CAN wires heavier gauge and twisted pairs then disapere behind the dash. Can someone please shed some light on this problem before I get Carted off in a white van. I have rang auto electricians and they wont touch it as they don't understand the can system.
I don't think even taking this car to MB indy will help not unless they have come across this issue.
Your input would be much appreciated.
Sounds as if you have some sort of global low voltage fault. This can be at the supply end---- short to earth pulling other systems down/ faulty alternator electronics etc or my favorite ---- poor systems earths----- somewhere in the system where there's intermittant voltage drop across a high resistance path to earth leaving low voltage for the electronics. I would check every earth point you can find on the wiring loom [ Mercedes love to hide these under wings, behind cladding/trim and on the bulkhead buried behind the dashboard] but start with my all time favorite the engine earth strap.
Thanks Graeme for your reply and was hoping out of all the members you would answer(Had to google your name that's-Graham in England).
Paid £35.00 to just-Answer and no one replied at all with their abundance or Merc Tecs just dying to help?? All i wanted was someone with knowledge of Star software on a daily basis as Iv only ever used the Snap-on for airbags and torn off ABS sensors and the MaxiEcu for my own cars.I am 500 hours into this issue as i never ask for help till now.

Well this old lady has been off road in a Barn sipping sherry for years and started with 11.5 volts at the battery, so I'm sure the engine earth is good.
Thing is everything works.From the electric roof to the heated seats. Even the drivers seat cushion recognises weight and allows the Hood to be operated that's a real safety in mind device with kids alone in the car. Clever bit of kit for 20 year car. I had every earth off and cleaned up with a dremil.

My background. 7 years Honda Uk Tec. 30 year's Bodyshop owner for MB and Lexus. 3 Years Mclaren MP4 12c. So i'm not new to re shelling cars and not metal chassis cars as in SMC Supercar. Earths mean everything.

My biggest concern is how this car can be taken out of park with no key in the ignition.How can that system fail. That should be a Can C issue and light the dash up like blackpool tower but doesn't.
On Star the EWM (gear shifter) "is not there"that's why I changed it even though I can select all the lower electronic gears and the inhibitor is working. The EGS51 has no faults.No banging into gear as in limp mode.Car shifts fine.Kick down works fine. Clear gearbox adaptions and it learns very quick within 10 miles.
Another strange thing is "i cant get the warning lights back on" with the engine running.If I could then I could do the steering wheel angle sensor to ask to be reset using the left/right x 3 procedure. Which maybe would then open the gateway to drill down these modules playing up.
I do have some area's to eliminate as in the after market Tow ball wiring fitted with dreaded Scotch locks. Going to take the whole wiring off and run continuity either side of were these locks cut into the wires. Also someone has run a wire from the of offside light loom right to the back of the radio wiring. This has tape on with reverse written on it. Its not connected to anything. Radio illumination is also supposed to drawn from the offside rear light? According to WIS. Radio also has a signal from the rear ABS sensor that turns up the volume in relation to wheel speed. Now this is really getting over complicated to get a radio to work. Best Regards Gary
Thanks anyway Graeme,
Yes I'v seen these articles.Seems Can B is everywhere even when there's direct live and earth in-place.

Best regards Gary
Just want to pass info on about your can voltages and why can l has higher voltage than can h.
They are both exactly the same but mirrored so can l starts at twelve volts and goes lower and can h starts at 0v and goes higher.

Hope that clears that up?

As with the car maybe a bit of water ingress in to wiring or fuse box/Ecu box somewhere?

Maybe more than one fault you’re dealing with
Thanks for that,so the voltage returns from the module after doing its job like moving a seat. Well i would love to know were my voltage drop is as I have nothing like 12 volts to start with.
Checking for water and dry joints and I have opened up every module,fuse box,relay and nothing. BAS unit under the servo PCB board had a slight residue on one corner but that just blew off and polished up with tooth brush.Then replaced with another one anyway.
You would think that much voltage drop would be a short to earth somewhere and a flat battery but that's no the case. Battery- to earth strap 0.25 amps draw. Very light spark on connecting up.
Had all the front carpets up and its bone dry,all the lower dash off and glove box. Opened all the sill panel plastic cable tracks looking for cooked-frazled-damp-dried out connectors and nothing. Door cards off ,all modules dry and and work. Seat memory's still there. I can have it connected to Star for two hours and the car still starts fine.
Drivers seat did do something odd when moved all the way forward as the headrest went right to the top. Who has 2 foot legs and a neck like a giraffe.
Need to take some pictures of the screen shots of the Interior Canbus as seen using the DAS as someone who's used to looking at Star values would go "look at that you dongo" That aint right. Check blah blah multiplug under heater blower.

Also using Xentry it shows were to measure the k line voltage to the N15/5 gear selector. Diagnostic plug X11/4 pin 12. (7-16 volts) "there is no pin 12" just a hole in the socket. Ok! so maybe I have the picture up the wrong way so turn it round and pin 12 is still not there. Had the whole plug out and nothing is broken, missing, torn out.Its just no pin 12 on that 38 pin hole socket.Hope the picture uploads.
Star recognises car vin number and model then sends me up the garden path.
Any ideas are welcome this stage Gents.
Best Regards Gary


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