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Outstanding Contributor Always Remembered RIP
216 with everything. 2002 SL500 with everything. 2009 SL500 with everything.
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6,543 Posts
Discussion Starter #1 (Edited)
This is a guide to the CAN bus in the 230 it applies to all models right up to 2008ish. This is not an explanation of how the CAN and WAKE UP work, it is a guide to a simple way to know if your car is going to sleep, and how you can check with just 2 voltage checks. We are only dealing with CAN B as this is where all of the problems usually are.
The instrument cluster has its own Robert Bosch CAN and not included here.

An outline into the CAN.
The CAN is a high speed data bus for communication for the electrical components in the engine and body, it is also used for fault finding as any faults are logged and stored to make fault finding easier. The CAN has 2 wires only, a twisted pair these carry the CAN H for high, and the CAN L for low, should a fault occur in one of these lines, the CAN will still work on the other one, but slower.

What is a CAN System?
A CAN system is:
A digital communication link between multiple Electronic Control Modules (ECM)
A 2 wire, bi-directional communication link with data transmitted
according to priority
Message specific addressing
CAN C - Engine CAN (also known as chassis CAN)
Fast communication speeds 125 kbps or 500 kbps

CAN B - Interior CAN (also known as body CAN)
Communication speed 83 kbps

Information from CAN C can be sent to control modules on the CAN B or vice versa via the Electronic Ignition Switch (EIS). The master, the EIS is the only control module that can transfer the messages and is known as the gateway.

CAN C has priority over CAN B as CAN C controls the actual running of the car and all safety components.

First, an outline of the connectors in the 230. They are known as X connectors (please note the all these connectors have a locking bar that un clips across the top, and the plugs cannot be removed until this locking bar is released)
The first connector in the passenger side foot well is the X30/18 Wake up with wires coloured green/white, this connects to the ignition switch.

The second connectors that also come from the ignition switch the X30/15 is the start of the CAN bus. All CAN bus wires are coloured brown and brown/red except the inter connects that join the 3 CAN connectors, these are coloured brown and brown/black.

So if there is a fault somewhere on the CAN it is quite simple to remove a brown and brown/black inter connect plug to isolate the the fault. Normally one would start with X30/15 and remove the interconnecting Brown and brown/black from connector X30/16. Now a voltage check can be done, if all the correct and normal voltages, then that interconnect can be put back and move on to the X30/16 and remove the inter connect that comes from X30/17, again check the voltages and if all are correct one can concentrate on the last one , the X30/17.


X30/18 First one next to X30/15 in the left sill is the CAN C. these items seldom give any problems in the car not sleeping or any CAN faults.

EIS (N73) Ignition switch
IC (A1) Instrument cluster
SCM (N80) Steering column module
ECM (N3/10) Engine control module
DTR (N63/1) Distronic
ABC (N5/12) Suspension
ESM (N15/5) Electronic selector
ETC (N15/3) Electronic transmission control
ESP (N47-5) ESP

X30/15 The second one in the left side sill is the start of the CAN B.
EIS (N73) Ignition switch
IC (A1) Instrument cluster
SCM (N80) Steering column module
DCM-L (N69/1) door controllers
SAM-FL (N10/10) Front SAM L
AAC (N22) Air con
LCP (N72) Lower control panel
ESA-L (N32/1) Seat adjustment


X30/17 in the rear fuse box.
RVC (N52) Vario roof
SAM-Rear (N10/8) Rear SAM
PTS (N62) Parktronic
TPC (N88) Tyre pressure control
KG (N69/5) Keyless go
BNS (N82/1) Battery power supply
TELE AID (A35/8) Not in UK early cars
COMAND (A2) Comand
PSE (A37) PSE pump

X30/16 right side front sill
SAM-FR (N10/11) front SAM right
OCP (N70) Over head control panel

DCM-R (N69/2) Door control L and R
SD (N55) System diagnostic connector
ESA-R (N32/2) Electric seat adjustment

Please note that Green/white wires are all wake up.
Brown and brown/red are the CAN H and L
The wires coloured Brown brown/black are the interconnects from the preceding connector or it goes to the next connector.


To test the CAN

A simple voltmeter is all that is needed, to measure any CAN voltage it is easier to lift the complete strip connector, on the rear there are 2 metal strips running the length of the connector, one is CAN H and the other CAN L.

If the car is all good and sleeping, that is with nothing running or active CAN L will have 11volts and CAN H 0.025 volts. If the car is active and one can make it active, just turn on the comand or open a door and you will see CAN L drop to 4.65 volt and CAN L go up to 0.65 volt. This voltage change when the CAN is active only last for a second and it should revert back to the dormant voltages.

When checking the voltages you must wait long enough to be sure that something is not going to try and start up, and that the car really is sleeping, that is with 11volt and 0.025 volts respectively. If these voltages are correct, then no fault.

In some cases one CAN line maybe short circuit, if this is the case then the CAN will still operate in most cases on the other CAN line, it will be much slower to operate and execute comands, this is known as the single line mode. Again this is easy to check by using the voltage checks above.

Its good if you can to keep the plugs in the same sockets on the connectors, there are no markings on the CAN plugs or wires to say what they control, and they will be positioned as in the diagram above.

This is the chart for the voltages present when active and sleeping (no activity on the CAN


Please note that if the comand has been used for a journey, you must wait up to 1 hour, for it to shut down completely.

Re any multimeter being used on these test, the meter should be set to the fixed 20 volt range, using an auto ranging meter will not work, as the CAN signal has passed before the meter can update.
 

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Outstanding Contributor Always Remembered RIP
216 with everything. 2002 SL500 with everything. 2009 SL500 with everything.
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6,543 Posts
Discussion Starter #2
If the above article is good enough, could it be moved to a sticky somewhere please.

I can do an extension to include the 202,210 215 and 220 in less detail, only the voltages are different.

Thank you

Malcolm
 

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W221 & Audio Moderator
2013 S550
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10,914 Posts
Thank you, Malcom!

I am certain owners of those additional models would appreciate the information. I am adding this to the W220 S-Class Encyclopedia sticky, in the section that discusses CAN bus, so I KNOW there are W220 owners who would appreciate it.
 

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Outstanding Contributor Always Remembered RIP
216 with everything. 2002 SL500 with everything. 2009 SL500 with everything.
Joined
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6,543 Posts
Discussion Starter #4
OK I will start on an addition for the 220 and 215 as they are the same in this respect, while I have some info to hand it would be better if I can add the location of the connectors.
 

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Registered
2003 SL55
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479 Posts
If the above article is good enough, could it be moved to a sticky somewhere please.

I can do an extension to include the 202,210 215 and 220 in less detail, only the voltages are different.

Thank you

Malcolm
Good work Malcolm :thumbsup:

am in the process of making a global sticky so will add this one to it.
 

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Outstanding Contributor Always Remembered RIP
216 with everything. 2002 SL500 with everything. 2009 SL500 with everything.
Joined
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6,543 Posts
Discussion Starter #6
Thank you :)

I am in the middle of another for testing the electrics in general.
 

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Registered
W220 S350/S500 2004
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386 Posts
it is a guide to a simple way to know if your car is going to sleep, and how you can check with just 2 voltage checks.
Can you tell why one would want to check it? Is it possible to use this technique to check if there is parasitic battery drain?
 

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Outstanding Contributor Always Remembered RIP
216 with everything. 2002 SL500 with everything. 2009 SL500 with everything.
Joined
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6,543 Posts
Discussion Starter #8
Can you tell why one would want to check it? Is it possible to use this technique to check if there is parasitic battery drain?
In many cars when there is a battery drain, the fault may not be the usual door and seat controllers. Some cars wake up and go to sleep, the only way a car will not go to sleep is if the CAN bus is still active once you have turned off, and locked the car. The first check should be done with a clamp meter that can resolve down to milli amps dc. For most cars post 2000 (new models) the drain on average is 55ma, so you have drain if this figure exceeds this by some margin.

Some well known things from a few years back for a car not going to sleep were.
Comand
OCP
Telephone ECU
Battery modules.
SAM

The idea behind what I have written is to make it easy with just a volt meter, you do not need a scope to check the system out.

Anything connected to the CAN could cause a problem.
 

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Outstanding Contributor Always Remembered RIP
216 with everything. 2002 SL500 with everything. 2009 SL500 with everything.
Joined
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6,543 Posts
Discussion Starter #10
My idea was to put the whole thing into a more simple language, and how to test for faults with a simple volt meter, an oscilloscope is not required.
 

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2004 E55
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624 Posts
Hi Malcolm,

My issue is on my 2003 sl500 with the instrument cluster, it doesn't transmit any data on the can bus and I cannot communicate with it from my star das/xentry, I can talk to every single module in the car except the instrument cluster. It works fine no issues at all, I even put it into another r230 and I can communicate with it just fine.

Thanks, Mike
 

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1 Posts
Hi Malcolm,

My issue is on my 2003 sl500 with the instrument cluster, it doesn't transmit any data on the can bus and I cannot communicate with it from my star das/xentry, I can talk to every single module in the car except the instrument cluster. It works fine no issues at all, I even put it into another r230 and I can communicate with it just fine.

Thanks, Mike
Hi Mike,

I have exactly the same issue with an IC from an R230 SL600. It worked perfectly fine in the car, including access via DAS/Xentry. I have removed it due to upgrade to an AMG IC and using it now in my test bench. It reacts perfectly fine on CAN-B traces, but it does not send any message! :-|

I am wondering if you have identified the root cause? That would be extremely helpful for me, since I am at a loss. No clue why the iC is not transmitting. Beside the CAN-C there is only a hardwired input from SRS, but even with those inputs missing it should transmit, shouldn't it?

Cheers
Robert
 
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