Interesting...1999 is probably a bit early for that Bosch to be running one of the usual ECU update protocols like UDS. It sounds like it's in the bootloader and looking for a valid executable. So the FW updater is likely in the bootloader.
replyIf you can open it up and find the JTAG pads, it should be simple-ish to use a JTAG reader to dump the image and then you can figure out the update protocol from that. It's unlikely to be complicated.
Not sure about your specific car, but a lot of the “consumer friendly” options like OBDeleven, Carly, etc are fantastic. You often have to pay, but a lot of work goes into them and they often just work.
reply> All that is to say, this space is ripe for some open hardware/software love.
replyThere's just so many computers and what-not in modern cars that this is a very tall ask. You'd need a project on-par with HomeAssistant to get anywhere.
Yeah, it seems like more modern technology has settled on standard protocols (maybe a naive impression--someone will shout at me if that's the case) but there's probably a very long tail of bizarre false starts if you want full coverage of models back to the early 90s when computers became more commonplace.
replyAfter 2006/2007 nearly everyone did CAN. I think that is even mandatory in the US, though I have no clue how to look that up (I assume there are details and exceptions) However before then everyone did their own thing. Often with custom chips that haven't been made since 2004 (or even 1999): good luck finding one that works if it breaks. CAN is cheap and allows a lot of power while hiding most of the protocol complexity. The things before that were often not as powerful as CAN, while being in practice a lot more complex because the complexity wasn't hidden.
replyI remember getting that era working. I concluded Mercedes was trying to be clever in making a protocol so complex nobody else could understand it (thus ensuring you had to use a dealer) - and then discovered they couldn't debug it.
replyeach body model (nothing to do with year or style) was different so clearing dtc but nothing else is not a surprise.
i did get that working, but I last touched it in 2007 so I don't remember enough details to be helpful. good luck.