Do the faults come back when cleared? Dan. 🇨🇦 2013 L405 5.0 SCV8

The MS-CAN is capable of operating 'one legged' so its unlikely to be a wiring issue unless there is already one leg down. Can you list all U codes on the vehicle please?
Are there any modules on that network that are not reporting any DTC's?
It's possible that there is a module shutting down that is a pass through and interrupting the flow of messages. The alternator will not be connected other than the ECM not receiving data from the ATCU so the charge strategy will be affected, a symptom not a cause.

Phoenix wrote:

The MS-CAN is capable of operating 'one legged' so its unlikely to be a wiring issue unless there is already one leg down. Can you list all U codes on the vehicle please?
Are there any modules on that network that are not reporting any DTC's?
It's possible that there is a module shutting down that is a pass through and interrupting the flow of messages. The alternator will not be connected other than the ECM not receiving data from the ATCU so the charge strategy will be affected, a symptom not a cause.

Another thing to mention is when the CAN system goes down. I can not lock the car from the key. I also can not start the car as it says smartkey not found.
Many thanks.

harryboy wrote:

When the MS can network is down i can't scan or pick codes up on any of the pictured modules, but these codes will be stored when the network is back online.

Thank you again Phoenix for your help, I really do appreciate it.
The HS-CAN system works entirely without fault when the car goes in to MS-Can tantrum mode.
There aren't even any warnings on the dash in tantrum mode other than I notice things like the Auto high beam assist, park sensors, can't lock the car, can't start car unless key held to column. And then eventually the battery charging system or low battery fault will come on. Instruments etc. all work fine. Car drives fine other than steering feels heavy, wipers go slow as the battery voltage drops from 14.4 down to around 12.
It's weird because the car works absolutely fine for a day or two with the new batteries or when I fully charge the battery.

Went out and measured the resistance and it was 62-64 so I'm guessing bang on.
Another thing to note is there was a lot of rain the week the car started having the issues; but i'm not sure if this is just a coincidence or if there are some common places water may have got in from puddles etc.

The frustrating thing is i'm sure this is something simple, it's just diagnosing it seems to be a problem. I don't have any facility to connect to the MS-Can and diagnose this way; but i'm guessing this would reveal the issues? Would a local Indy have this facility or is it delaer only.

Also my other thoughts were maybe the alternator is becoming intermittent and thus battery voltage is dropping and causing issues on the MS CAN network? Just find it strange that the car seems fine when the batteries are fully charged up as if they are masking something.

Thank you again for taking the time to help me

Right, found the diagram (it's in the Wiki as part of the workshop manual) attached below.
Firstly, you need to identify what modules you have installed, if the HS-CAN is staying up then there's a good chance the Gateway module is OK, I'm now re-evaluating the voltage issue as it shouldn't go that low just with lost comms. It is of course possible that the Gateway module is faulting or losing power, it directly connects to the alternator and the BMS so given your issues, it's the most likely culprit at this stage. If you can, get access to it and check the connectors for security, damage, corrosion and if you can get hold of appropriate test pins, pin grip.

None of the above should be prohibitive for an indy that isn't 'afraid' of communication issues, it's just basic electrical diagnostics (and to be fair, not all dealer techs are entirely comfortable with it either, but they at least have, or should have, a trained and experienced Diag / master tech to take over.) If you have the time and confidence, it's nothing that can't be done yourself with a minimum of reliable test equipment.

https://www.fullfatrr.com/gallery/albums/u...ody%20.pdf


ETA - battery voltage would have to be below 10.5VDC, you would also get low voltage DTC's detected on other systems.
It's also important to realise the difference between DTC's for missing messages and 'bus off', the former indicates a module has not received an expected message from another module, whereas the latter indicates collisions (on the network!) detected or other conditions that are preventing communication (shorts to +ve or -ve, malformed packets etc.).

Given that the CJB & GWM are the end of line modules, you can unplug any other module on the MS-CAN without disrupting the integrity of the network, the EOL modules are the only ones reporting 'bus off', it is possible that another module is spamming the network - unplugging them would reduce functionality but should prove network hardware resilience...

I keep coming back to the charging and lighting issues though, both of which use the GWM....

Apologies for the ramblings - I'm just working through the wiring diagram, the door modules and wiring through the door harness flex connector could be a source of the problem, you could try opening and closing the doors and manipulating the harness in the rubber boot to see if it provokes a response - the same goes for the upper tailgate flex connections, again though, that shouldn't cause the GWM to inhibit basic functions just because it turns off the MS-CAN.

Just noticed there is a fault showing in the PCM in one of the above photos - what is it please?

Thanks again, we are getting somewhere on this.

Correct; HS-Can is staying up without fault.

My car does appear to have most of those modules on your wiring diagram. Something which may be of note, someone has removed the running boards/side-steps at some point and left the connectors dangling by the cills. They were corroded and short circuiting and full of mud. I just disconnected the entire running board module in the boot (early on in my testing as I initially suspected this could be the issue?). However it made no difference. Do you think this may have caused some irreversible damage to something?

Well my next course of action will be to inspect the GWM and see if there's anything obvious going on. Would it be worth buying a second hand one of a car with similar spec to see if it works?

With the whole network going down am I correct in thinking that the problem is either the GWM or the junction box - central? (just to check, is this the fuse box behind the dash?) As they have the terminating resistors?

The weird thing is on my initial fault codes Parking Aid is on the HSCAN but this fails and stops working when the car goes in to tantrum mode and then will work again when the car is normal Not sure what relevance this has...

I can't thank you enough for taking the time to help! You're probably bored of hearing it haha.

The deployable side steps / running boards shouldn't be an issue if you've disconnected the control module, I've never known CAN of any speed to not recover (sometimes after a couple of ignition / power cycles) once the source of disruption is removed. I'm not sure if the GWM is a 'one shot' device, when I worked for a LR dealer, we did change a few but they were always new (obviously), maybe contact GAP first to see what their procedure is for re-coding. The KVM is, without a doubt, a one-shot device, if you add a trailer module you have to replace the KVM.

Yes, the CJB is the one behind the dash, with fuses & relays, next time the MS-CAN fails, can you measure the supply voltage at one of the modules, other than the CJB or GWM, it'd be best to expose one of them ahead of time so you can check the voltage with the minimum of fuss. The terminating resistors primary function is to stop 'reflections' on the network but also gives the ability to test network integrity, I've never known them to go 'bus off' just because they're EOL devices. It is possible that there is some powersaving mode that shuts off the devices on MS-CAN - but - there should be DTC's for low voltage / powersave initiation...
Without being 'hands on', I'd suggest checking the GWM more closely, one more question - does the system voltage drop before the loss of MS-CAN or after?

There was once something related to the electronic steering rack with a code improper shutdown? But I don't think this is relevant to anything as it only happened once or twice and I put it down to the very low voltage and there were a host of other DTCs.

Yes I'll check the voltage at one of the modules such as the drivers door module (assuming I check it whilst module is plugged in?)
I'll have a look at the GWM and see if there's anything obvious. I'll also have a look at the CJB to check this and the fuses.

I can't answer the last question accurately but I shall check it and see next time.

Thanks - nothing on the vehicle should suffer an 'improper shutdown' with system voltage above 11VDC, yes, you'll get low voltage warnings but everything should still work or at least communicate down to 10.5VDC and sporadically beyond.
Body system module voltage can be checked open circuit but is always better whilst connected - back probing the connector is better than potentially opening up the receptacles in the housing anyway.

Not wanting to teach any egg-sucking, when checking the modules, use all your senses and note anything unusual in the general area, don't just focus on the modules themselves. For example, look for condensation in the vicinity, listen for any relays activating or contacts arcing, check for localised heat or any 'hot electrics' smell along with the more obvious water dripping out of the module when moved or green connector pins / corroded screws.

Will do, thanks again for your help. Will report back when I have some new findings.