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W246 Hazard Light Switch Panel Not Working

Hamodi

Member
Joined
Feb 5, 2019
Messages
40
Location
London
Car
W221 S320L
2013 W246 B180 CDI

Couple of weeks ago the old battery died, jump started by RAC and driven to garage to get battery replaced. Noticed afterwards that the hazard light switch panel (hazard light, ECO and ESM gearbox buttons) all stopped working.

Since then, I've tried the following to get this working again but still unsuccessful:
- Disconnected battery for a couple of hours then reconnected.
- Replaced the hazard switch panel with the exact same part, A2469052001.
- Checked fuse box in passenger footwell which said 5A fuse #84 controls the hazard lights and ECO. Fuse seemed to be ok but changed anyway.
- Scanned all modules using iCarsoft MB II. The only error that came back was U100900 "LIN bus 2 has a malfunction" current and stored.

Has anyone come across this issue before? Is there a SAM that controls this switch panel? I would appreciate any pointers on where to look next.
 
Bump - would really appreciate any thoughts on this if possible :)
 
Tried searching but unable to find wiring diagram for Lin Bus 2. If anyone has access to this, I would really appreciate if you could send me a copy. Thank you :)
 
This has now been resolved.

Managed to get hold of WIS wiring diagrams. Traced it back to the upper control panel receiving it's signal from the battery sensor LIN. Went back and checked the battery sensor wiring, seemed okay at first glance, but after I undoing the connections I saw that the mechanic who had changed the battery had pinched one of the battery sensor wires. After freeing this cable, the upper control panel has started to work again. Obviously the damaged cable will need replacing to ensure longevity.

Another example of why I prefer to work on my own cars. In this case, unfortunately it's my mums car who lives 3 hours away and broke down with a flat battery so was towed to an RAC approved garage which she thought she could trust to do a simple battery change...
 

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