Hi all,

I have a very strange query. I have a W204 C250 CDI with 200,000km / 124,000m on the clock and I keep getting strange faults that come and go. For example - the "third break light" error will pop up for a few days and mysteriously go away( B16B715) , I also get a B179715 - left standing light 2 has a malfunction. There is a short to positive or an open circuit, but there is nothing wrong with the light, In addition I get the same for the right standing light but again, no problem with the light itself. I also get a C1076D86 'Circut 54' is unreasonable. There is an incorrect signal.

All codes are off a iCarSoft MB v1.0 with the latest version of software installed.
None of these seem to be valid faults but they are clearly generating error codes, what could be the cause of this. Is there a short somewhere that would cause these false reading/errors.

Any help would be appreciated ?

 

Your weird issue reads like a poor GND at R-SAM.
Marginal connections cause erroneous voltage to be measured by R-SAM the chassis lights control module.

While cleaning bad GND connections is easy, the hard part is locating where what circuit is acting up.
This is what makes a simple job complicated and time consuming....

The shortcut is to clean painted GND Posts comprehensively such as:

• Trunk area Right/Left
• (Footwell R/L)
• (Engine bay R/L)

-- Besides even the Rear-SAM can get showered from leaking rubber grommets overhead. Look for signs of dried moisture.

-- Don't discount low-voltage chaos abilities.... read chassis voltage while driving or listen to starter crank speed as an indication of battery charge...

-- Can you pls give us a report with all faults descriptions from every modules?
We need to see what modules are involved in your party. It's rarely party of one.
When the Rear-SAM computer is crazy unstable, it tells stories to its partner: the Front-SAM computer...


poor seals cause moisture damage courtesy @juanmor40
-- In addition, you can arm yourself with a tube of automotive high-temp silicone RTV to seal every exposed connector you come accross.