MR.AMG.

Hi people is there any auto electricians on here in the surrounding areas of Leeds UK? Or anyone with a good knowledge on electric faults on mercedes. I have fault codes and a scanner. I am a newbie to mercedes. I have tried all sorts with the help of good fellow people on this forum but no luck. The car won't start so i can't even take it to anyone. Thanks in advance.

CaliBenzDriver

Can you give us the background details that lead you to NoGo?

Is this ....
"crank/no start" or "No crank/no start"

What is your scanner telling you???

MR.AMG.

Hi i have a no crank no start. With my scanner i found can bus c and canbus b connector which had water damage I bought connectors off a different mercedes with the same part number but the wires were other way round so i wired it the opposite way to make it right if that makes sense. Please correct me if i have done something wrong. This is is what my scanner is showing...

CaliBenzDriver

You have gathered a lot of info already. The security modules are unable to allow crank request.


No crank!

Water damaged modules have limited survivability rate. You will need to
1 - Locate all bad modules then
2 - replace modules and
3 - program replacement.

Actually I forgot the 1st repair step:
FIX THE WATER ENTRY POINT ASAP.
No new/old module will tolerate soaking.

15/5
15/3
"mute" modules are missing....
More modules will wake-up when bad ones are removedvfrom the bus.

MR.AMG.

Are these the modules..

If they are then i have re wired can c and can b wires already. The only difference was the wiring was the other way round but the part number was exactly the same. How do i program this please?

CaliBenzDriver

this is not a module.... this is only a "bus distribution bar" used to inter-connect many modules on a particular CAN- B or C bus.

Each of these CAN cables is connected to a module at the other end.

MR.AMG.

Can you show me what a module looks like please and how do i trace it? R230 SL

CaliBenzDriver

Your chassis has about 40+ computer modules.

We've already established your 15/3 + 15/5 modules need to see you.

​​​​​​I don't know what modules your scanner is referring to by schematic numbers.

• Once you find out their english naming
• you'll need to find where they are located
• how to remove them
• what EPC current part number
• where to buy parts
• how to program replacements

MR.AMG.

I found this fault on my scanner too..

Thank you for your help so far

CaliBenzDriver

Great detective job with your scanner!

"smoking gun" located
Now we know WHY you're getting "No Crank" condition.


> Status:
Two of the main security modules (EIS + ESM) are disabling crank. These are the gear shifter plus the ignition key module upset by swampy bus bar.


> What To Do....
-- Concentrate on fixing the bus distribution bars we know got swamped. When that's satisfactory these two module will should come back clear and ready to enable start.

-- These modules are NOT defective, only CAN Bus itself is defective. You're savings stacks of cash by not replacing good parts in a hurry.


-- This is not a guarantee another module (F-SAM) is not bad. We'll cross that bridge when we get there, using your scanner.

-- We are going to eliminate the source of "No crank" then see what other faults remain.

++++ CAN Bus signals have polarity...
-- When you reworked your bus distribution bar hopefully you did respect CAN-HI/LO as being distinct signals.

-- Wiring just needs to stay identical regardless of colors being different with replacement cables.

MR.AMG.

Thank you for this information! ^^^

I will rewire CAN C green to green and green/white to green/white and the same with brown/ red on CAN B. The blocks i bought had the exact same part numbers just the colours of the wiring were other way round so i assumed to make it identical to the old block i have to wire it the opposite 😳

I will report back very soon 🧐

CaliBenzDriver

Yes, I think you got it:


> The chassis only care that each CAN Bus Hi+Lo signals still land in the same spot as it did originally.
Meaning CAN-HI/LO must not to be mixed up.

> The position where each connector lands on the bar is not critical but should be preserved because slots are assigned to individual modules.
Meaning connectors should not be mixed up.


> While the chassis is undergoing bus surgery, disconnect all batteries and charge them.
This break will provide a fresh reboot to help sanitize goody modules....

MR.AMG.

what am i doing wrong 😮‍💨

Still no crank.. these are the codes i am left with after scanning again..

CaliBenzDriver

partial fault list...

the top line shows cause for CEL/MIL as 15/3 + 15/5 being still faulty. This translates as... the engine is disabled because of the Tranny being disabled by missing "gear selector".


You can concentrate on....
the GEAR SELECTOR itself hosted by your Steering Control Module (solderless SCM). In other words the unstable SCM may be causing your no-crank by ripple effect.


Process of elimination:
Have you identified your CAN lines to unplug all but mandatory modules from now clean distribution bar.

MR.AMG.

The gear selector rod is broken 😢 do you think this is causing the no crank no start?

CaliBenzDriver

Yes, indeed. The ECU needs the gearbox to be in a safe gear selection.

You can read status with your scanner at both ends:
the SCM
the ISM

MR.AMG.

thank you for all your help! My car finally starts but this is not the end of it lol

CaliBenzDriver

Great, now you're empowered to face this challenge

MR.AMG.

Can't win with these cars 😒 but I'm not giving up on it!
is there a relay or a fuse for the coolant?