ISM Issue After Transmission Service
but fiddling around whilst some of the cables could be lose would bring some fun - and I'd suggest worth checking more carefully than finding something responds to a cursory poke then walking away




You really should trace this down properly. You may need to remove the carpeting on both front sides . BOTUS indicates lots of issues with the items under the passenger side from drains leaking into the cabin and getting under the floor. If I was a betting man, i would think the same could happen on the drivers side too. However I dont know what is under there so I defer to the real experts on here.
Again you might join the BenzNinja club, he can most likely hook up and tell you exactly what is wrong, where the issue is physically located and certainly can code any modules if they need replacing.
I've looked under the passenger area when I removed the LoJack and everything seemed clean and dry thankfully. I think something got fiddled down there on the driver side during the brake job when they had to use so much force to get the rotor off as well there were crazy strong pulsations when braking after the initial brake front pad and rotor change. I'm definitely going to take a better look it was late last night so I left it for now, but hopefully will have the chance tonight.
I also for example checked the drive train CAN distributor (X30/21) under the driver seat and the circuit board along with the plugs/wires look good physically. I'm trying to look for the drive train sensor CAN distributor (X30/38), which I believe may be in the driver footwell area since the picture I have shows it in the Front SAM area, but I think that must be for a 2007-2008 with dual battery system.
I may contact him as well. I think I need a good power source to keep the battery strong when doing the coding. I honestly did not think of this and it makes so much sense.
This whole situation reminds me of an issue I had with my CLK last year. Knock on wood, she's been good since.
https://mbworld.org/forums/clk-class...-car-wash.html




It might be possible that the mad pulsation after the brake issue damaged something, I think it would be from the rotor(s) not be installed correctly, wobbling all over. That could cause the ABS system to light off. So would the bearing and hub being damaged during the service allowing the hub to wobble. Mad pulsation would be from the ABS system then lighting off. .. Then again they might just have not re-connected the ABS wire back or damaged the brake pad sensor. Lots of things to actually lay hands on :-) Re rotors and hubs ..Check for lateral and vertical runout on the rotors and check the play in the hub/bearing. IIRC there is a thread on here re the front bearings/hub and getting it right.
Be very careful of mucking about in the drivers footwell with the batteries still hooked up ..you dont want to short something out and cause damage or even a fire....
If it was me, I would source another garage to do the mechanical work based on your experience..just sayin'
Last edited by WRC-LVR; Jan 23, 2025 at 09:39 AM.




It might be possible that the mad pulsation after the brake issue damaged something, I think it would be from the rotor(s) not be installed correctly, wobbling all over. That could cause the ABS system to light off. So would the bearing and hub being damaged during the service allowing the hub to wobble. Mad pulsation would be from the ABS system then lighting off. .. Then again they might just have not re-connected the ABS wire back or damaged the brake pad sensor. Lots of things to actually lay hands on :-) Re rotors and hubs ..Check for lateral and vertical runout on the rotors and check the play in the hub/bearing. IIRC there is a thread on here re the front bearings/hub and getting it right.
Be very careful of mucking about in the drivers footwell with the batteries still hooked up ..you dont want to short something out and cause damage or even a fire....
If it was me, I would source another garage to do the mechanical work based on your experience..just sayin'
I believe this as well. To also note, even after the rotors were changed out to a second new set, there was still some slight pulsation and I doubt the pads got deformed by that time. Thank you. Definitely need to get that wheel off and set what's up. As stated before, even the tire shop when trying to balance the wheels had no issue getting all the other wheels off except the driver side front wheel because two bolts were extremely difficult to remove and required replacement (The Visit Workshop Without Changing Gears warning popped up the first time when trying to put it into park at the tire shop before the work was attempted and it refused to go into park or reverse). I removed both front ABS sensors from the hubs and they don't seem to be damaged at all, but again visually can be deceiving since they're electrical parts. I never got any ABS warnings or codes stored in the vehicle. I found a video on how to test them. I didn't think of the brake pad sensor on the passenger side if that could be causing an issue.
My main issue regarding getting to a specialist has been not being able to put the car in neutral. Was hoping to just get it to do that and then have it towed off, but if I have to have it towed in park, I guess we'll have to come up with some creative measures to get it out of the garage and onto the tow truck. I have a family member that specializes in Mercedes and he has a DAS or Xentry system at his shop, I just don't regularly use him, hence why the car had gone to another shop. If the ISM is also indeed damaged at this point, I have found a specialist that offers repair services for these somewhat near me, so if I could get it off the side of the transmission and take it and bring it back it would help as well.




501C: CAN Signal 'Reverse Gear Engaged' From Control Unit ME-SFI Is Implausible.
Does anyone know where the front end can block is located?
Also, while inspecting the ABS pump, I noticed the bracket that holds three of brake lines is broken into two pieces and separated.
lots more CAN under the alloy plate less passenger footwell (lift up the carpet)
others say lots behind the drivers seat (around that vent (I’ve not bothered looking here yet)
I doubt its CAN faults - as I said battery volts and then the ISM is likely dead they ALL do it




501C: CAN Signal 'Reverse Gear Engaged' From Control Unit ME-SFI Is Implausible.
Does anyone know where the front end can block is located?
Also, while inspecting the ABS pump, I noticed the bracket that holds three of brake lines is broken into two pieces and separated.
Maybe use the tow truck sling to raise the rear end up and pull it out that way. Place rear tires on roller pads to pull up onto flat bed. Then have it taken to your family member with Xentry for proper diagnosis...Then report back
Last edited by WRC-LVR; Jan 24, 2025 at 09:55 AM.




lots more CAN under the alloy plate less passenger footwell (lift up the carpet)
others say lots behind the drivers seat (around that vent (I’ve not bothered looking here yet)
I doubt its CAN faults - as I said battery volts and then the ISM is likely dead they ALL do it
Yeah I want to get the ISM off as I found someone that has ability to both repair and reflash them.
Maybe use the tow truck sling to raise the rear end up and pull it out that way. Place rear tires on roller pads to pull up onto flat bed. Then have it taken to your family member with Xentry for proper diagnosis...Then report back
Thank you. I really appreciate this input for how to tow the car. I know the dealers have a free wheel adapter I read on here, so was going to check if my relative has that and I can pick it up to have the tow truck put on the wheel and send off to him.
Also, I decided to check my brake fluid this morning. Seems too high even after the front pads and rotors replacement (It's all the way up to where the inner cap mesh sits and is slightly seeping through the mesh).
The Best of Mercedes & AMG




Last edited by gaazmon; Jan 24, 2025 at 05:29 PM.








Two other odd things I noticed. When I hit the front driver side rim or the headlight with the palm of my hand, I hear a strange buzzing sound come from somewhere either around the rear of the headlamp area or further back. No such noise on the passenger side. As well, I just noticed when I turn the ignition on, the ABS pump / ESP module will make a constant clicking noise and it does not stop. I still think it's an ABS sensor or similar issue. The reason I'm leaning to this is because of a thread I found on here on the ML forums as well as a thread on another forum (Even though his vehicle had temperamental starting issues while mine started with temperamental ISM issues).
https://forums.mercedesclub.org.uk/i...ervice.198909/
He had a similar sequence of events as me: Took vehicle in for a Service A, transmission service (He mentions this later in the thread), as well as brake job. His solution was to replace all 4 wheel sensors and a relay in the front SAM (I tested that relay in my vehicle and it's working fine). I have also been getting sometimes codes show up in the Comand module scan (Shutdown due to low voltage), but they haven't come back since removing the brake pad wear sensor.
does it have air tragic suspension ? likely as it was std - you need to check (and likely replace) all three level sensor link rods - they seize and snap off - one each at the top inside of the front wheels - and one hiding at the back above the park brake actuator. These also operate the headlight levelling - which is driven from one master headlamp (I forget which one it is)
All the original issues sound like the garage messed up the brake disc replacement - I don't believe its possible to leave a car with ABS permanently active - that said I have had a motorbike with a dead rear ABS sensor leave the traction control permanently active and the vehicle became unrideable, as the engine power cuts out
I believe all along we said drive the car looking at live data from each ABS wheel speed sensor - if they don't match going slow in a straight line one is playing up - and must be fixed
there are always two parts to the sensor operation - the sensor and the bit that gives it something to be excited about - the reluctor - aka the lump of iron that disturbs the magnetic field the ABS module seeks to understand. On the Front - of non 4x4 models - this element is built into the inner wheel bearing seal
check the old seal in the picture below - the pattern on the black bit is magnetised brake disc gunk, reacting due to magnetism in the seal face, they come smooth like the new one - you can only clean and check it by removing the front hub - no amount of trying in situ has any effect. If the front wheel bearings are way out of adjustment that could also lead to issues.
rear suspension level sensor link rod - and the silly bracket (holding the ball) that snaps each leg off one by one over time - till the car drops to the floor and becomes undriveable
.
Last edited by BOTUS; Feb 7, 2025 at 06:02 AM.




Last edited by gaazmon; Feb 9, 2025 at 08:47 PM.
even so some filth like, moisture, combustion gases, acids, and oil mist can wander down the engine loom and blow the brains out of the engine ECU - quite common, quite expensive, quite a nuisance
if this happens either replace the engine loom (whilst replacing all the other bits) - or go to great lengths to flush out the crud or you blow up the new ECU
I'd start with cleaning up corrosion / gunk - if brave pry open the engine ECU and use contact cleaner - do not use heat, its not needed and tends to make the aged sealant sticky again - manipulate the silly cover back to normal before refitting with appropriate sealant - when apart clean and look for blown capacitors - they die from heat and as they leak can blow up the chips beneath that control the coil voltage - YouTube videos of those specialist repairs
might get lucky just cleaning things up




even so some filth like, moisture, combustion gases, acids, and oil mist can wander down the engine loom and blow the brains out of the engine ECU - quite common, quite expensive, quite a nuisance
if this happens either replace the engine loom (whilst replacing all the other bits) - or go to great lengths to flush out the crud or you blow up the new ECU
I'd start with cleaning up corrosion / gunk - if brave pry open the engine ECU and use contact cleaner - do not use heat, its not needed and tends to make the aged sealant sticky again - manipulate the silly cover back to normal before refitting with appropriate sealant - when apart clean and look for blown capacitors - they die from heat and as they leak can blow up the chips beneath that control the coil voltage - YouTube videos of those specialist repairs
might get lucky just cleaning things up
Could it be transmission oil seeping up through the plug at the transmission not engine oil?
Last edited by gaazmon; Feb 10, 2025 at 04:57 PM.
try cleaning up as best you can - if you think water ingress got in the ECU opening and drying would be the best thing to try - then clear all the faults - start it up and check after a 10 min drive
I don't think trans fluid could get in here - but its beginning to sound like you need to try some other modules - why are you so confident the ISM is good - they built them to die and that's what they do - but now you throw a curve ball and the engine one might be a close second








1. There is brown stain on the side of the padding. It's dry and don't see anywhere else on the padding, only on the side that touches the side frame. Looks like rub-off from that liner along the frame. Felt a bit around down there too and no sign of dampness or water yet.
2. I found a loose bolt hanging around by the wire loom and I believe this is what caused that short the first time around when trying to poke around down there. I realized right away where the bolt is supposed to go. There is a screw in the side panel by the AUX battery mounting that didn't seem to belong. This bolt matches the other two there so I removed that screw and put this bolt back in it's place.
I doubt though there's any water issues with this vehicle. In the last 8 years since ownership, it's always garaged and only has been driven about 16k miles in that time. I don't think it's even seen rain in that time. It was purchased from a local Mercedes dealer and was dealer serviced by the previous owner according to the CarFax.
when you go to a garage they forget / don't care about w221s emptying full batteries in a few seconds given half a chance - open the door leave the key on, 10 mins later it will be mostly flat - these things eat so many volts then almost need plugging in to recently upgraded nuclear power station on permanent basis










