S-Class (W221) 2007-2013: S 320 CDI, S 350, S 450, S 500, S 550, S 420 CDI, S 600

Locked W221

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Old Oct 9, 2023 | 06:28 AM
  #1  
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W221
Locked W221

Hi everyone.
My 2010 W221 is locked and does not react to any of my two keys. Not a single light goes on.
The driver-side door is impossible to open with the emergency key (I assume the lock was changed by the previous owner(s) for a reason unknown).
I was able to open the trunk and get to the rear SAM module but have no idea how and where to connect the spare battery since it's an MOPF model, there is no secondary battery in the trunk.
Can you please advise? Breaking the window or calling the lockpick guy is not quite an option for me at the moment.
Thank you.

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Old Oct 9, 2023 | 08:18 AM
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2008 CL550, 2022 EQB 300, 2023 EQS 450 4Matic
I had this happen a few months ago. Did you use the proper procedure for using the mechanical key? I think you have to turn it twice in a row. I got in, and oddly the car started right up with no issue.
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Old Oct 9, 2023 | 08:23 AM
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W221
the thing is I can not turn the key in the door. I only succeeded with the trunk. I assume the lock on the door was changed so my key does not work anymore there
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Old Oct 9, 2023 | 08:40 AM
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W221
The car will start up since for that purpose, it uses a different battery which il located under the hood, and not n000000004039, the tiny one under the dash.
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Old Oct 9, 2023 | 10:43 AM
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its usually the boot key that is stuck from a build up of all the road filth - wd40 and a toothbrush then wiggle and wiggle it usually goes (its NOT force that gets it to go - might take you 15 mins) - I'd try that on the door (don't forget its never been moved for 13 years)


how did you open the bonnet ?


if not I'd consider - of course any errors playing will be a big mistake !!! - I'd find a perm live around the edge of the fuse box (the bit you are incorrectly calling the SAM is really the SRB - they clip together and you normally see the view like the diagram below - from inside the car - looking in after lifting the plastic cover once you folded down the rear seat arm rest )

right side as you look in from the boot where some option stuff gets its power (I think) is some Perm Live points - then put a gentle charger on it and see if you can get it to come round after an hour or so....



in this pic (back to front to how you'll see from the boot) 133 to 140 I think are perm live outputs - there are two massive power wires but I'd be careful play with them....


115 50A Heated rear window
116 10A Engine 157, 275, 278: Charge air cooler circulation pump Engine 156: Engine oil cooler circulation pump S 400 Hybrid: Circulation pump 2 power electronics
117 15A Rear cigarette lighter
118 30A Engine 629, 642: Fuel pump 15A S 400 Hybrid: Circulation pump 1 power electronics 15A Engine 642.8, 651 from 1.6.11: Refrigerant compressor with magnetic clutch
119 7.5A Front central control panel
120 Reserve
121 10A Audio tuner control unit
122 7,5A Control unit COMAND
123 40A W221: Front right reversible seat belt pretensioner
124 40A W221: Front left reversible seat belt pretensioner
125 5A Voice control control unit (SBS)
126 25A Ceiling Control Panel
127 30A Seat back lower pump Pneumatic pump for multicontour seat Air pump for dynamic seat adjustment
128 25A Engine 156, 157, 272, 273, 275, 276, 278, 642: Fuel pump control unit
129 25A UHI (Universal Cell Phone Interface) Control Box / Ceiling Control Box
130 30A Electric parking brake control unit
131 7.5A Antenna amplifier module above the rear window
133 15A Trailer recognition control unit 5A Rear view camera
134 15A Socket in luggage compartment
135 7.5A Radar control unit (SGR) PTS control unit (PARKTRONIC)
136 7.5A Engine 642.8: AdBlue® control unit
137 7.5A From 1.9.10: Rear view camera
138 5A Navigation processor (Taiwan, before 8/31/10) Emergency call system control unit TV plug/tuner connection (Japan)
139 15A Refrigerated box in the back of the rear seat
140 15A Cigarette lighter plug with ashtray light, rear Socket 115 V
141 5A Rear view camera control unit Rear view camera power module
142 7.5A PTS control unit (PARKTRONIC) Radar sensor control unit (SGR) Control unit for video sensors and radar sensors (from 1.9.10)
143 25A Rear seat control unit
144 25A Rear seat control unit
145 20A AHV drawbar connector, 13-pin
146 25A Trailer recognition control unit
147 Reserve
148 25A End sleeve terminal 30 panoramic sliding sunroof
149 25A Panoramic sliding sunroof control module 150 7.5A Combo TV tuner (analogue/digital) TV plug/tuner connection (Japan)
151 20A Trailer detection control unit 25A Electric parking brake control module
152 25A DC/AC converter control unit 7.5A Antenna amplifier module above the rear window Relay M Terminal 15 relay (2) / reserve 1 (changeover relay) Н Relay terminal 15R O Socket relay P Heated rear window relay Q Engine
156, 157, 275, 278, 629: Circulation pump relay S 400 Hybrid: Circulation pump relay 2 power electronics R cigarette lighter relay S Engine 642 except 642.8: Fuel pump relay Engine 642.8, 651 from 1.6.11: Magnetic clutch for refrigerant compressor S 400 Hybrid: Circulation pump relay 1 power electronics
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Old Oct 9, 2023 | 01:37 PM
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Hiring a locksmith is going to be much cheaper than breaking the window and then having it replaced.
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Old Oct 9, 2023 | 01:39 PM
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Originally Posted by nath_h
I had this happen a few months ago. Did you use the proper procedure for using the mechanical key? I think you have to turn it twice in a row. I got in, and oddly the car started right up with no issue.
The procedure I know that works is that you turn the key and pull rapidly.
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Old Oct 9, 2023 | 02:07 PM
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W221
Locksmith hired. The job's done. Some of the ECUs went rogue and drained both of the batteries. Now the fun part begins, to figure out which one of them ECUs is guilty.
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Old May 24, 2025 | 12:50 PM
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Originally Posted by alien2k1
Locksmith hired. The job's done. Some of the ECUs went rogue and drained both of the batteries. Now the fun part begins, to figure out which one of them ECUs is guilty.

how did the locksmith do it, in the same position but my key turns but pulling the handle 3x won’t pop up the lock tab
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