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Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4495
Experience:  15 years master certified 100% fix rate and have access to factory radio codes, wiring, and instructions.
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We have a Mercedes SLK 200 that is draining the battery

Customer Question

We have a Mercedes SLK 200 that is draining the battery overnight. It was invovled in an collision and we replaced the airbags, dashboard, seat belts and had the airbag ECU repaired. Everything was acquired from a UK airbag supplier that sells airbag kits and repairs ECUs etc.The drain was traced to fuse #45 (Fuse N10/1F45) Brown armada airbag control unit (N2/10) Airbag Indicator & Warning Lamp (A1e15) 7.5 Amp rating.Remove the fuse and the drain drops offConnect scantool with fuse removed and we get the following fault codes:1) 9002 Stored & Current - Control Module N2/7 (Restraint Systems Control Unit) (Circuit 15R) no voltage when voltage present at 152) 902D Stored & Current - The component or the signal line to the component B48 (Front Passenger Seat Occupied and Child Seat Recognition) has open circuitWhen the fuse is refitted the above faults clear but 3amp drain on the battery comes back.
Submitted: 2 months ago.
Category: Mercedes
Expert:  Lou P. master tech replied 2 months ago.

Hello, my name is***** and i will do my best to assist you.I am going over your story now and will reply back soon with some info,thanks!

Expert:  Lou P. master tech replied 2 months ago.

The fuse not only power the airbag module but it powers the weight sensor module under the passenger seat . Unplug the module and see if the draw goes away .

Expert:  Lou P. master tech replied 2 months ago.

The module has an 18 pin connector but only 10 pins are being used . It is a module mounted to the track of the seat . Hope this helps . I will have to step away for a bit but will check back as soon as I can .

Customer: replied 2 months ago.
Lou, We disconnected that module under the seat as you recommended and still have that 3amp drain.
Expert:  Lou P. master tech replied 2 months ago.

Ok then unplug the airbag module and see if the draw goes away . Make sure not to turn the module over or tip it

Customer: replied 2 months ago.
We disconnected the airbag ECU and the drain goes away. We have removed it and presumed the fault is in the ECU and that it needs to be replaced. Do you agree?
Expert:  Lou P. master tech replied 2 months ago.

that is a fair assumption. let me take a look at the wiring diagram one more time to see. but i agree with that.,

Expert:  Lou P. master tech replied 2 months ago.

yeah the power supply is a straight shot from the fuse box to the airbag module. so i think the module is the issue, that is the best i can suggest at this point. since there is nothing else attached to that power wire.

let me know how it goes.

Please take a second and click the stars at the top of the screen to rate me so i may receive my credit , 5 stars is ideal , please request me in the future.Keep in mind then when you rate it does not end our conversation, you can still return here to me for follow up information if needed just simply reply back, thanks!
Lou P.
Master Mercedes-Benz Technician
Master ASE Certified

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