beingapoorv

I have a really strange situation with W221 (Single Front Battery model). After ignition is turned off, there is a massive drain of 5.5Amps, observed via Multimeter connected in series across Negative terminal.

This drain is intermittent in nature. Comes up for 30 some sec and goes down to 5 mAmps for 10 seconds and then again goes up. I hear clicking sounds coming from Front SAM, ESP, Starter solenoid and god know what other solenoids, but all these clickings are intermittent and drags to drain to 5+ Amps. I have tried removing all relays from SAM and the fuses to no luck. Only when I remove the Pre-fuse to SAM that is 150 Amps pre-fuse, the drain comes down to 300 mApms and stays constant.

BOTUS

puddles on canbus systems ? ever pulled up the front carpets....they pull up from pedal area towards the the seat (unlike any other brand of car)

BOTUS

if that seems fine maybe try another prefuse box off ebay

FYI in general Mercs love their SAM to take a bath - it helps fill their coffers - worth a check often circuit boards all furry !

beingapoorv

Checked CAN bus as advised. No puddles. No corrosion detected. Also check Front SAM, no white corrosion on the board.

I observed and realised that Car stopped beeping when locked/unlocked since many days. Also the Siren when alarm goes off seems to be feeble and lasting for a second only. Other than this every electronic inside works perfectly fine. Can the siren/alarm/no beep be related to Front SAM not going to sleep ?

BOTUS

alarm has own battery pack - they can go bad and cause big issues - certainly worth a check

packs on ebay cheap - anyone with a 10 plus year old car should be swapping them out

https://www.ebay.com/itm/163004369117?

beingapoorv

I think I messed up.

In pursuit of checking where the leakage was I removed one fuse at a time and inserted back while checking the Amp draw on multimeter. I finally found the f****ing culprit. It was Electric Parking Module.

But what I did grave before this was, Disconnected the CGW to check if CGW was the cause of drain. I disconnected CGW while battery was connected.

Now after finding the culprit, I started the car, and f**k all the Dash Light are up, No gauge is working, Command is Off. Car starts fine, Runs fine but nothing functions on the dash (guage, gear indicator etc). AC is working but Command is off so can't see anything. Radiator fan is On full speed.

I am fearing that I messed up bad. Can you gyide me mate @BOTUS 😭😭😭

BOTUS

MIGHT JUST BE COMMS FUN

disconnect the battery for 20 mins and reconnect.... CGWs like to get themselves muddled

beingapoorv

Reconnected battery after a day and started the car. No improvement. Dash lights are still up, command not working, power windows, soft close not working, radiator full on speed. Car starts fine, runs fine.

What should I do ? Will clearing the codes help now ?

BOTUS

umm, not sure. its the problem with modern cars, so much to play up - going to have to go bit by bit with good diadgnostics

CGW is not a simple thing to swap on these - lost of run setting them up and linking chassis number etc.

beingapoorv

Called the Scanner guy with Xtool with MB All system scan capability. Scanner was unable to connect to any System. Looks Comms issue with every system including ECU and other.

Any ideas how this would have occurred ? and what to do next ?

BOTUS

well the one bit with its finger always in every pie is the CGW, and as you mentioned you threw a spanner at it - its got to be the first one to investigate, they often get over with a battery reset - but its not guaranteed

I guess double check fuses as free and simple - then if inconclusive, drop trim above pedals and pull it out - fiddly but simple (small plastic/metal box, on wires from diagnostic socket (it unclips from above / beside throttle pedal), with it in your hands, check sticker and get one secondhand off ebay for not much - then u need a genius to fight it to think your car is the one its meant to come from.... then see where you are

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trigital

CGW is spelled like Central Gateway...so Gateway is like the router in your house, without CGW most of the modules can not talk each other. Disconnect CGW again, dissemble the connector to search for humidity, also you can easily open the cover from CGW to verify. Install everything back if no water traces, all should be ok if the fuse for CGW is still alive.

In your car, any scanner does not scan modules one by one. Just ask the CGW to broadcast the query to each module, so if scanner receive no answer, then CGW is not connected, defective or has fuse blown