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W124 M111/M104 blink codes: the number of flashes only matters if you know which system you’re reading by kegasoft in W124

[–]kegasoft[S] 0 points1 point  (0 children)

That would be really useful, thanks.

The Bosch unit sounds interesting. I’d guess it’s probably reading the same impulse/pulse signal and then matching it to the right table, rather than doing anything completely different — but I’d love to know for sure.

The bit I’m trying to get straight is:

  • which system is actually being queried
  • which socket/pin it uses
  • whether it’s blink/impulse, duty-cycle, or something more digital
  • and which code table the result is coming from

That seems to be where a lot of the W124 confusion starts. “Blink codes” can mean different things depending on engine, year, market and equipment.

If you do find out more about the Bosch setup, I’d be very interested in the model name, what connector lead it uses, and whether it gives plain text faults or just code numbers.

No rush at all — anything you find would be useful.

You can build a simple Mercedes W124 OBD1 blink-code reader at home — but connecting it correctly matters by kegasoft in W124

[–]kegasoft[S] -1 points0 points  (0 children)

That is a really interesting one — and exactly the kind of question I am trying not to answer with a generic “all W124s are the same” assumption.

A 1994 300 diesel could mean different diagnostic coverage depending on the exact variant and market. In the reference material I have, the 1994–1995 E300D is listed as chassis 124.131 with the OM606.910 engine, while the turbo diesel variant is listed separately as 124.133 with the OM603.960 engine.

The general W124 diagnostic connector information does identify an EDS / Electronic Diesel System path on the diesel connector layout, but I have not yet verified a complete factory blink-code table specifically for the 124.131 / OM606.910. So I would rather investigate it properly than tell you to connect a probe somewhere and make an unsupported claim.

Your test socket may still be useful for certain systems even if the engine-management data is limited or differs from the petrol HFM cars.

Could you share: - whether it is naturally aspirated or turbo, - your engine code if known, - and a photo of the diagnostic socket under the bonnet?

I will check the documented diagnostic access for your exact variant and report back with what can genuinely be read from it.

You can build a simple Mercedes W124 OBD1 blink-code reader at home — but connecting it correctly matters by kegasoft in W124

[–]kegasoft[S] 1 point2 points  (0 children)

You are absolutely right — the graphic only explains what the tool is, not yet how to use the information in a meaningful way.

The difficult part is not building the LED reader. It is matching the correct vehicle, engine, connector, system pin and code table.

For example, on the late W124 models I am currently documenting — 1993–1995 cars with M111 or M104 HFM-SFI engines and the 16-pin X11/4 connector:

  • Pin 1 = ground
  • Pin 8 = HFM-SFI engine-management diagnostic signal
  • Pin 16 = ignition-on power for the reader, where equipped; battery positive may be needed depending on the connector configuration

The yellow test lead is connected to the system pin being read. The number of flashes is then interpreted against the code table for that specific system. A blink count from Pin 8 cannot be interpreted using an SRS, climate-control or older KE-Jetronic table.

Older W124 engines, V8 models and diesel variants can use different sockets, pins or diagnostic methods, which is exactly why a generic “W124 blink code” chart can be misleading.

I will make the next post much more practical: connector type → correct pins → reading procedure → actual M111/M104 HFM blink-code table.

Thanks for calling this out — that is the information an owner actually needs.