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Discussion Starter #1
Hi all, I'm a new member in need of help.

I'm after the ECU wiring diagram for Mercedes CLA.

Long story short...I accidentally sparked the ECU body with positive battery terminal and now my remote key don't work to unlock/lock doors. Also I have to provide earth/ground to ECU for it to power up and enable car to start, I've done that by simply getting a piece of wire from chassis to ECU body. If I remove the ECU earth connection made by me the rad fan comes on and the car don't start and doesn't not go in gear either. Also has the message saying "Anti-theft protection activated". On OBD scan it's says "Air quality sensor malfunction, there is an electrical fault" also the ignition lock doesn't work either.

So was wondering if the 2 are linked?
 

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Good grief!

May wanna consider a search on virginized ecu and remarrying / replacement
 

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Well i would install new front sam. I am not sure if it needs to be coded to the car. 2014-2018 Mercedes CLA250 C117 Front Fuse Box SAM Control Module Unit BCM OEM | eBay
It sounds like you fried ground circuit maybe it make to pay mechanic to trace wires. I would start with sam. I don't believe ecu is blown because car starts. You keep saying you need to add ground to ecu and electricity traveled over ground and i am sure it melted burned ground circuit in your sam.
 

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Discussion Starter #7
Well i would install new front sam. I am not sure if it needs to be coded to the car. 2014-2018 Mercedes CLA250 C117 Front Fuse Box SAM Control Module Unit BCM OEM | eBay
It sounds like you fried ground circuit maybe it make to pay mechanic to trace wires. I would start with sam. I don't believe ecu is blown because car starts. You keep saying you need to add ground to ecu and electricity traveled over ground and i am sure it melted burned ground circuit in your sam.
Thanks for that, I'll try get this checked out. One thing I was wondering was does the ECU has any sort of connection? I've seen another car where ECU body has no connection to earth or positive.
 

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I doubt body of ecu has direct ground connection to body but you can search for youtube ecu videos they show ecu with removed top cover.
 
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