13 Button OBC Code Plug Matrix

[Klug]

I found this little picture buried on bimmerforums- it is the part number and differences between the 13 button OBC Code Plugs. Handy for all those doing OBC swaps and need to find out their correct coding plugs.

I'm looking for #21 (Late model M20B25) and I've been striking out!

[Steve Corbett]

I bought a complete set up and installed in my 89 325I. Car is being sold after I get the front end back together. I am pulling OBC out before it goes away. I will see what coding plug it has but I am pretty sure it was correct.

[Blacke30vert]

Swap code plug from original obc

Can I swap my old code plug from the original obc into a new to me obc? I have a 3.8 version I believe is from an e car and I have a 325i

[CharlesMerlen]

Still searching ODC Plug TYP 4-6 1385941 ? I've got one to sell.

It's delivery with my kit but, originally for 325i.
I change the plug for my 323i. Not use now.

PM me.

[george graves]

Somewhere I have that in a easier to read format. Yes, the OBC and even the cluster coding plug is a little eprom. It too bad really, and it doesn't allow to adjust for everything.

[Andrew325is]

Has anyone ever done a readout of the coding plug? I read here it's a "fuse-programmed ROM" so it can't be overwritten, but how about programming a new ROM?

[bmwman91]

I have always thought about dumping the ROM contents from a few different ones and determining what the scaling factors are so that I could make custom ones. Never got around to it, though.

[george graves]

I have always thought about dumping the ROM contents from a few different ones and determining what the scaling factors are so that I could make custom ones. Never got around to it, though.

Unfortunately, it's not scaling factors or values. It's just a flags for what is installed. (I'm 99% sure of that, I look into it years ago - and it wasn't worth messing with) - there is a guy on ebay that sells aftermarket ones. After all it's just an 8 pin DIP eprom on a board - nothing else.

[bmwman91]

Hmm, so just flag bits in the plug, and the MCU in the OBC has an internal table from which it uses the flags to select scaling values? I opened one and checked the chip PN once, and IIRC it was a 32 byte parallel ROM device or something.

[george graves]

Hmm, so just flag bits in the plug, and the MCU in the OBC has an internal table from which it uses the flags to select scaling values? I opened one and checked the chip PN once, and IIRC it was a 32 byte parallel ROM device or something.

Afraid so. With the price of PCB's dropping, a better hack would be just to remake the main board in the cluster. There is one after market version out there since at least 2000-ish. It's really not doing all that much processing wise? No? Keeping track of miles? And driving a few things???

[bmwman91]

A project that I used to have a lot more enthusiasm for was a "Super OBC". Basically, retain the OEM buttons & display, but put in a more modern microcontroller with a serial-USB interface for programmability and data logging. It already has input for wheel speed and injector pulsewidth, and splicing in a tach signal would be super easy. If nothing else, simply being able to tweak the parameters related to fuel economy would be cool. It could all be done with pretty minimal components these days, rather than the hilarious collection of passives and logic gates, along with a 4 bit microcontroller that the original ones run on!

[george graves]

"4 bit microcontroller" I didn't know you could make a UC with 4 bits - that would be a interesting thought experiment. 4 bits, you sure couldn't do anything that was more then 0-16????

[Andrew325is]

Who is knowledgeable on the differences between the coding plugs? I need one for an M42, but they're NLA, for both fuel tank sizes. They're still available for the S14. Would one of those be more accurate than the one for the M20 I have now? They're both DOHC 4 cylinders.