My car started to act up recently and I'm stuck solving this fault. The car is a 2003 E400 CDI. Several modules show errors that they either cannot send or recieve messages on the interior canbus. System diagnosis shows error code: 9313 – Interior CAN bus: short circuit in CAN lines / CAN bus low short circuit to GND - Current. My CGW has a part number of A211 445 25 00

I checked the CGW connector, no corrosion on the module or the harness plug either. But with a multimeter I can measure continuity between PIN 1(GND) and PIN 9(CAN-B Low). Then I removed the carpet, to check the X30/7 distribution plug, but there I couldn't find a short, not even on the plug that goes to the CGW. I cleared the faults, drove the car a bit, and they come back almost immediately after starting the engine, every time.

I have access to WIS, Xentry DAS but I cannot think of how to proceed with the troubleshooting, any help is greatly appreciated.

 

Most likely one module killing the CANBus; been there, done that, got the T-shirt twice.

I have a couple of posts on CANBus diagnostics for my W210 E55. Those will give you some tips. Advanced search upper right

Also, take a look at this:

https://mbworld.org/forums/w211-amg/...ml#post8985282

 

Also this:
https://mbworld.org/forums/w211-amg/...ml#post9215132

Be sure to look at the attachment and not just the links.

WIS with electrical schematics available at charm.li.

 

Thanks for the links, I will look thru them. Someone here suggested that I should try and change the CGW module. Do you happen to know how to code in a used second hand CGW module?

 

EDIT: When you open the door (amongst many other things) the W211 CANBus wakes up. You will need to let it sit for 10-20 minutes for it to go into "sleep" mode. Just so you know why the voltages show "awake" when you check the voltages a few minutes after opening the door.

How do you know it is the CGW? Do not fire the parts cannon until you know where to aim. Gets very expensive and frustrating otherwise.

Check the voltage levels on the CAN-Hi and CAN-Lo lines. A low-ohm resistance to ground will cause both voltage values to be incorrect as I posted in the W210 diagnosis.
-Multimeter(s) connected to X30-7; two multimeters (one for the Hi line and the other for the Lo line make it a bit easier and quicker). Note voltages with CANBus asleep with key off. Then turn key to position 2 and note the voltages with the CANBus awake.
-Pull connectors out of X30/7 one at at a time; if voltage values remain incorrect, reinsert the connector and go to the next one. Repeat until the voltages on the CANBus display correctly. That connector connects to the faulty module. Only remove one connector at a time and do not mix them up. Each connector should correspond to the electrical schematics in WIS (Mine did. Others have reported differently.)
-Go to the the suspected faulty module and pull the connector from it. If you like, for piece of mind, check for continuity from the X30/7 connector to the module connector and also to chassis; that ensures you are at the correct module in case WIS does not match your build.
-Go back to X30/7 and plug the connector back in while leaving the module disconnected from the harness. Do voltages display correctly? If yes, you found the faulty module you need to replace. If no, then I would look at a wire grounded to chassis due to abrasion or pinched under a mount or washer (unlikely but possible).

On my W210, it was a 95-ohm short on the CAN-Lo line internal to the rear door window control module. The second time, I didn't even bother measuring the resistance; I just pulled connectors from X30/7 one at a time until the voltages displayed correctly. There was no doubt about it; with connector at the rear window control module plugged in, voltages vastly incorrect at X30/7. Connector at window control module pulled, voltages on X30/7 immediately displayed correctly. I ended up replacing both rear window control modules on the car. First one was a learning experience, the second one took literally minutes to diagnose.

Remember, a short on the CAN-Lo line anywhere in the circuit will kill everything since every module is connected to the CAN-Lo line.

Best way to reprogram a CGW is to use STAR/Xentry to pull the coding from the old module, then reprogram the replacement with the coding from the previous module. If you have to reprogram a CGW from scratch, that involves using the vehicle data card and programming each item as present/not present. I've never done it so I cannot provide more advice. Whatever you do, do not attempt to reprogram your current CGW while in Xentry; the data is erased and the computer attempts to reach the servers in Germany that have the file for your car (which will now be "bricked" and require a flatbed to the dealer so they can reprogram it (assuming the CGW is good). One, maybe two instances in the W211 sub-forums where a member did that and bricked their car.

 

I didn't have much time, but did some testing anyway.

With the key in position 2 I could measure 0,6-0,7 Volts on the CAN-B High side. If I understood correctly that is a good value, and it means the communication between modules takes place as it should.
However, the CAN-B Low side didn't show any signs of life, 0 Volts each time I tried measuring. I disconnected some plugs - one at a time - from X30/7 but nothing changed. Here I should measure 4,65 Volts if the system was in good working order, I think.

I will continue the search for the faulty module, and also have a look at the connectors X30/4 and X30/6 at the passenger footwell.
The 66 page long PDF about the CAN system showed Xentry DAS screenshots where it's possible to monitor the CAN system communicaton whether it's stable or not. Unfortunately tho, I couldn't find that menupoint in my DAS system.

 

Yep, that's a dead short on the CAN-Lo. You will have to go to the other block connectors and do the same thing.
FWIW, I actually found it easier to use a multimeter and the CANBUS monitor to troubleshoot.

 

Not sure if this one will assist but check out pages 6 and 13.

 

I spent this afternoon with searching for the short, and I've concluded that this car is full of surprises. Thank you bbirdwell for the PDFs, they were a huge help.

I started with the X30/6 connector, then X30/4 and finally X30/7. The faulty module (or wiring) is the driver electronic seat adjustment/dynamic seat control unit. After unplugging this module from X30/7 the error about shorted can lines didn't come back. Unfortunately the connectors order did not match to the order that WIS showed me.

I was about to go for a test drive when i heard the idle speed fluctuate a tiny amount. When I looked at the dash I saw the dreaded red battery - visit workshop error message.
With my multimeter, I measured the charge voltage which was a bit too high for my liking - 14,9 Volts , with occasional fracture of a second long spikes of almost 16 Volts. Then I ran a quick test on the car with DAS, and found a new fault code in the BCM: Code 9055, The terminal 61 signal on the CAN bus is missing or is faulty. If there is no specific customer complaint, ignore fault code 9055.

Funny thing is, the alternator voltage regulator was changed, approximately 6 weeks ago, because the original one didn't manage to charge higher than 13,7 Volts. The first replacement Bosch unit was dead, with that there was no charge voltage at all, and the second bosch unit worked fine up till now.
Could still be an issue in the can lines, or did this regulator just die on me? I have the original and the other bosch regulator still in my garage, but to change them for testing would be a really painful job to do again.

 

Is code 9055 "current" or "stored". Current indicates a problem right now and stored means it happened sometime in the past.
You can reset the BCM by disconnecting it from power and signal for about 10 minutes. There is a tech bulletin that indicates if there is a low voltage condition at any time the BCM will might go into a "Safe" mode that effectively takes the BCM offline. I posted on the procedure a month or so ago; I'll have to search for the posts. You can, however, find this information in the technical bulletins in the WIS download from charm.li (you can also just peruse the WIS online rather than downloading the .zip file). There is a section that will walk you through an end-to-end test of the entire charging system.

FWIW, AlexHemi on this subforum had (IIRC) two failed voltage regulators in a row despite the fact they were "new" parts. He also replaced his BCM after discovering that a failed BCM can default to a low-voltage (~12.9 volts) charging mode. When I last talked to him a month or so ago he resolved the voltage/charging issues. Alex is a very high-tech individual who stays busy with his consulting work in the petroleum/aerospace industries. Smart guy whose posts are worth reading.

Personally, with the voltage spiking such as you describe, I would attribute it to a faulty voltage regulator. I and others have found that even though the box may say Bosch, the part is not German but rather a cheap Chinese manufacture. Zooming in on the photos online can sometimes show the "Made In China" molded into the Bosch part.

Warms my heart to hear you zeroed in on a faulty module. The seat control module has been described in multiple posts as draining battery with a >1 amp draw when the system should be asleep. You are the first to my knowledge to attribute the module to a CANBus failure.

 

Another wonderful two days have I spent trying to figure out what is going on with the car.

I partially removed the driver's seat, and managed to determine that the short to GND seems to come from N32/19 - Dynamic seat control module.
The electronic seat control module had some corrosion looking substance on its PCB, but it measured okay even before cleaning that.

About the charging error. BCM logs the "terminal 61 signal missing" error as current and stored, and also the engine control unit has the fault code P2010 - Generator Communication fault as current and stored. Xentry gave me some instructions to measure voltages at the driver's SAM, to see if the terminal 61 signal is okay there. The specs are, for my car at least, 1-2 Volts with ignition on, and 11-14,5 Volts with engine running. My measurements were 40 mVolts with ignition on ,and 70-85 mVolts with engine running. In my understanding that means that the almost brand new voltage regulator failed completely, and the alternator is working now 100% when the engine is running, that's why I get 16-17 Volts at idle.
I'm going to remove the alternator, have it examined and refurbished by a professional. Unfortunately I will only have time to do this next year.

In the meantime, I'm going to remove N32/19 and check it, hopefully it can be repaired.