Dead Chassis Batt now Most Sprinter Electrical Systems Fail

[ArcherTC]

Hello all -- found my trickle charger disconnected yesterday and chassis battery dead. I charged the battery and engine started right up. I've since driven a number of miles and restarted the engine a dozen times without problem except ...


I have multiple Sprinter electrical systems not working ... SRS, lights, wipers, electrical door locks, fuel gauge, climate control ...


Check engine light and SRS lights on, brake warning lights on.


Obviously an electrical component failed/fried or a system reset needed. Nearest Mercedes dealer is 2 hours away and I'm reluctant to drive much with all these systems out.


Any tips greatly appreciated!


David J

[Mansderm161]

I don't know the answer but you might be able to call the Mercedes service department and give them the info you provided. It may be a simple thing to reset.

[Lily&Me]

A sprinter dealer may be able to help you, or RV service center.


Maggie

[Titus]

When goofy things happen to computers or garage door openers first thing I do is remove power for 30 minutes. On the garage door opener this means unplug it. On a laptop computer this means remove the battery. So... I would disconnect the Sprinter at the accelerator pedal and wait a while then plug it back in. Be sure that the engine has been shut off at least 10 minutes before disconnecting - there are some after-shutdown things that have to happen before removing power.

[ArcherTC]

Thanks to all ... I think Titus has it right. I did talk to a service tech at MB who recommended disconnecting the battery then after 10 minutes doing a "hard reset" by connecting the (+) and (-) cables to each other (Not the battery of course!). He said this will help discharge any current remaining in the onboard computers.



I followed his instructions and it helped temporarily ... fuel gauge read properly, didn't have time to check other functions though as the SRS warning light came back on and the other systems then failed again. I'm giving it another try with a longer disconnect etc. but at least I'm encouraged that it's not a component problem but rather low voltage error codes that need to be cleared.

[tgilton]

I have exactly the same issue. 2018 GT with 400 miles on it. No evidnce that my battery was low, but van was fine until I packed it up and was ready to leave. Then, exactly as you describe: SRS error, fuel gauge dad, AC and seat heaters dead, lights don’t work, sensors dead, check engine light on, parking break light one, etc. Got towed to mercedes dealer. Dealer says Airstram patched into Canbus with “aftermarket radio” and this caused problem. Then they wanted me to fetch it up and pay for time since it wasn’t a sprinter warranty thing. Obviously this is NOT the problem.

Turns out, it is a setup thing in the Fusion headunit. Just heard from my AS service guy and he is bringing Van by my house (while I was writing the above). Says there was recently a service bulletin from Fusion about this, and AS corporate is now aware of it. I do not yet know exactly what the setup thing is, since he is going to explain when he arrives. I will post when I learn the fix.

[tgilton]

Okay. The Fusion headunit appeared to somehow find itself in the wrong mode after a hard reboot. There is a setting ("settings" then "system") that lets us choose CAN mode, and that was in PSM mode. The device must have rebooted when we disconnected the house battery, and came up in the PSM mode, which pissed off the CANbus and all the signals went nuts for the sensors on the bus. Once our service guy tapped the CAN mode, all the sensors and everything worked correctly... Now, the OP's problem might be different, but the symptoms are the same as mine, and mine is now fixed with this setting selected correctly. Just go into settings, and scroll down to the CAN mode option and pick CAN. If that isn't it, I wait with baited breath to what the solution is to your problem!

EDIT: Mine is a 2018, and I understand that the bus setup might be different for different years, so just be aware.

[ArcherTC]

Wow, Tgilton, amazing ... never would have guessed the Fusion unit could cause this problem! I will try your fix this morning and let you know.


Please tell me who your tech guy is in case I need to contact them, thank you for the information!

[ArcherTC]

A note for anyone else with this problem, tgilton was right. Under system settings on the Fusion unit there are two menu entries for the CANbus. The first looked like it was selected okay but when I tapped the second options were "PSM" or "direct" (I think). Mine had PSM selected. As soon as I changed it all the electrical system problems resolved !


Thanks so much to tgilton, helped resolve a huge headache for me !!!


David J.

[wachuko]

Great news!!!

I need to store this in a non-volatile memory section of my brain in case I run into it

[Titus]

Maybe my Kenwood isn't so bad after all.. Far as I know it does not cause problems with the Sprinter CAN (knock on wood) and does not kill my chassis battery.

[Mansderm161]

I find this interesting. I had a bad chassis battery on my 2018 AI and Mercedes just replaced it. I assume they disconnected everything and would be clueless about fusion? Yet everything works with new battery. Was your problem related to the battery going dead or related to the trickle wire?

[Alex AVI]

Originally Posted by tgilton

which pissed off the CANbus and all the signals went nuts for the sensors on the bus. Once our service guy tapped the CAN mode, all the sensors and everything worked correctly.

First, glad you and AS tech figured it out. BTW - it is so easy to get settings messed up with Fusion. Happens to me a lot just by cleaning the screen, sees it as a "swipe" function. So I clean screen only when Main Disconnect is off

Second, this is the main reason why everyone should stay away from the CANBUS (different thread - Bypass Fusion GPS nanny filter). One wrong move or even a discharged battery and boom, things can cascade into major issue and blow up in your face. Some CANBUS errors are easily reversed by fixing underlying wiring/component that caused it. Others pull up a HARD code that can't get reset without expensive dealer intervention.

[ArcherTC]

To answer mansderm161 ...


I keep a trickle charger on the chassis battery because of the Fusion current drain issue. Last week it got disconnected and I found the chassis battery dead (probably no charge 5-6 days ). I charged the battery and the RV started right up but all the electrical issues I mentioned appeared.


My understanding is that the Fusion did a "hard reboot" and in the process the CANbus setting got changed and subsequently scrambled all the Sprinter communication. I believe this is a random event so disconnecting the chassis battery won't always cause this fault.


BTW, I recently updated the Fusion firmware to the latest version: 3.6. Don't know if this version is more susceptible to this fault.

[Alex AVI]

Originally Posted by ArcherTC

To answer mansderm161 ...


I keep a trickle charger on the chassis battery because of the Fusion current drain issue. Last week it got disconnected and I found the chassis battery dead (probably no charge 5-6 days ). I charged the battery and the RV started right up but all the electrical issues I mentioned appeared.


My understanding is that the Fusion did a "hard reboot" and in the process the CANbus setting got changed and subsequently scrambled all the Sprinter communication. I believe this is a random event so disconnecting the chassis battery won't always cause this fault.


BTW, I recently updated the Fusion firmware to the latest version: 3.6. Don't know if this version is more susceptible to this fault.

Sorry for long post below, just no way to say it in a paragraph or two. Read on if you want to be bored

I think you are right in that disconnecting battery won't always cause this fault. The chances are probably higher for these faults to happen with battery charge degrading over time.

Reason for this is there is a minimum 2 to 3 CANBUS'es (depends on make, model). CAN-C is the chassis bus & high speed. CAN-B is the interior (some call it Body) bus, low speed, & fault tolerant. There may be a separate CAN-D which is a diagnostic bus. The issue is they operate on differing speeds and slightly differing differential voltage levels. This makes for some "unpredictable" behaviour as voltages drop over time, in case of discharging battery vs. a quick clean battery disconnect. So when power is back, all nodes/modules report on the bus and all is ok. Though some won't reset until certain drive cycles are satisfied (i.e. emissions modules).

In the case of Fusion setting getting scrambled due to hard reset, it most likely presented itself as an identical module that already exists when the bus started to poll. So now, the bus is confused. The good thing is since Fusion is not part of CAN-C which can pull a hard, non resettable code, fixing the Fusion settings allows CAN-B's fault tolerant protocols to decide that all is ok.

So a question you may ask is why would a device on CAN-B pull up a code for a CAN-C ? Because info from CAN-C can be sent to modules on CAN-B or vice versa via the Electronic Ignition Switch (EIS). The EIS is the only control module that can transfer messages across buses, like a gateway does. Yeah, I know, so they are separate buses, but yet they are connected.

[ArcherTC]

Alex AVI -- thanks for your reply. Interesting but I must admit beyond my understanding of the communication details.


I do want to be sure it is clear that the central problem seems to be the Fusion system settings. The installation instructions mention that the unit can be installed in CAN or PSM mode. The Airstream default is CAN but apparently with the hard reset the Fusion system settings switched to PSM, which is what I found when I checked my unit. This apparently triggers the communication issues for the Sprinter.



Switching back from PSM to CAN mode immediately resolved my problems.


David J.

[Alex AVI]

Originally Posted by ArcherTC

Alex AVI -- thanks for your reply. Interesting but I must admit beyond my understanding of the communication details.


I do want to be sure it is clear that the central problem seems to be the Fusion system settings. The installation instructions mention that the unit can be installed in CAN or PSM mode. The Airstream default is CAN but apparently with the hard reset the Fusion system settings switched to PSM, which is what I found when I checked my unit. This apparently triggers the communication issues for the Sprinter.



Switching back from PSM to CAN mode immediately resolved my problems.


David J.

Yes, you are correct. The PSM is just a way for certain hardwired devices to also be able to interface/connect to the CANBUS-B. The Fusion is dual-capable. CAN has unique 2-pin cable & plugs into CAN bus distributor behind front dash trim under headlight switch. PSM has a different unique 2-pin cable that connects to PSM connector (either under driver seat or under dash, not sure where it is on my '17 Sprinter). BUT regardless of which cable is used, only 1 can be physically used, not both, because the other end connects to same pins on Fusion wiring harness. So if CAN cable is connected and Fusion setting reverts to PSM, then CAN will complain. If PSM cable is connected and Fusion setting reverts to CAN, then PSM will complain.

As a side note, even if you were to use PSM cable plugged into PSM connector & Fusion wiring harness, it would not work because PSM is not programmed for the Fusion system.

[TMorristown]

Originally Posted by ArcherTC

Hello all -- found my trickle charger disconnected yesterday and chassis battery dead. I charged the battery and engine started right up. I've since driven a number of miles and restarted the engine a dozen times without problem except ...


I have multiple Sprinter electrical systems not working ... SRS, lights, wipers, electrical door locks, fuel gauge, climate control ...


Check engine light and SRS lights on, brake warning lights on.


Obviously an electrical component failed/fried or a system reset needed. Nearest Mercedes dealer is 2 hours away and I'm reluctant to drive much with all these systems out.

I had a similar issue in 2016 Interstate GT. Battery went flat while at Airstream shop for a repair. When I picked it up, I had a variety of flashing (very short blinks) for SRS, for ABS, etc. Looked really bad. Essentially everything on CANBUS had a problem, even the fan on the HVAC and the window lift motors would stop briefly as a warning flashed on the dash display. The van was drivable, but it sure made me nervous

I checked on Sprinter-Source Forums and found a tip to check the brake switch at the top of the brake pedal lever. There's a white switch (on the engine compartment side). I pressed it backward (toward the driver). I heard a click, and ALL THE PROBLEMS WENT AWAY!
I'm not sure if the switch had already come loose, then the battery went flat or if someone bumped it. I hope this is helpful to others.