Older K bikes are fitted with ECU's that use a Texas memory chip type 87C510-15JT. These chips are Dodos and pretty obsolete. The numbers on the ECU chip are B5846 which is a Bosch part number, produced for BMW by Texas.
These old memory chips need different hardware and software on the ECU board. Many cheap programmers won't handle them and the firmware programs in later BMW ECU's are loaded into later, cheaper and more easily sourced memory chips.
The chip reference after the dash in the part number is the speed. This oem chip is spec'd at (15) 150nS which is pretty slow by today’s standards, but ok for engine management processing.
MY 1997 KRS DOES NOT HAVE A PROBLEM WITH THIS ECU. IT RUNS LIKE A TRAIN!
However, better gas consumption would be nice and others with older bikes and ECU's may one day be faced with a dead ECU and don't like the price charged by the stealer. K1200 ECUs have many different part numbers. In this early example the circuit board, memory chip, and code will be different to later oem replacements. Trying to understand what the differences are between BMW ECU part numbers will drive you mad and I suggest you look at the old and new photos to try to work out which you may have. I have never worked out from their labels what's exactly inside the box.
There is very little scope for taking the old ECU any further. My old ECU is labelled Bosch 1 465 232. Even the chip tuners had to make a special adapter board. If you have problems with one of these then read on.
At some later time which I think may be post 2001, BMW came out with a new ECU hardware design using the later memory chips M27C512-12B3. These are the OTP or One Time Program type with a speed of (12) 120nS. They are compatible with the ubiquitous 27512 memory chips which can be got with UV erase windows and electrically erasable versions. Both these types allow the program in memory to be erased and replaced.
I wanted an ECU I could try to update with the later memory chip, and maybe even try some tuning chips and play with map codes. Much has been posted about the K- Bike idle and stumble and pi**sed most of us off. Many got a BMW warranty swap done free and the less fortunate stumped up megabucks for a stealer oem part. I believe that around 2003 and later there may have been some ECU changes that were not fully effective creating more unhappy owners. So I wanted the ECU that stumbled and had write ups because I knew this would have the later board and eprom. The ECU label ends in 166 - see photo.
My used 166 ECU came off a USA K1200GT 2003. Now there could be some issues. I think the ECU handles some of the cruise function and early KRS's like mine don't have cruise. My 166 ECU came at the end of last year waiting for service time (Now). The very latest ECU listed has a label ending 296. I acquired a .bin file dump not knowing if it would be compatible with the 166 ECU board.
I could have blown the 296 code into UV programmable memory but didn't want to mess about with UV erasure. I have a Chinese Willem universal programmer board - clunky to drive and not for beginners! I decided to use a Winbond W27C512-45Z EEPROM. These don't have UV windows and look more like the oem chip. These are 45nS, faster than the oem but probably don't need the speed in this application.
With the blank Winbond chip programmed with the 296 ECU code I set about the swap. The ECU case requires a 'security torx bit' - That's a standard torx with a hole in the center. After removing the 4 case screws, you carefully work around the case cover separating the cover from the silicon bead (without damaging the silicon bead). Cover off you do the same thing to lift and remove the board. You need patience working around the edges as the cover and board are stuck quite firm.
With the board removed you can locate the memory chip bottom left which ha a white plastic clip over it to stop it jumping out. Push a needle down the slot in the top to push each locking tab outwards and remove the cover.
Check the oem chip type underneath their silver parts label. It should be a M27C512-XXXX. Replace with the new pre-programmed chip being careful to straighten up the pins so none get bent. Re-fit the white locking clip and ECU covers.
Remember I said there was nothing wrong with my old ECU.
Turned on the key and got the fuel pump whirr (That's an ECU function).
Rolled the throttle back and forth a few times.
Pressed the starter and the bike went to about 1150-1200 rpm and held steady.
Rolled the throttle on and off and the rpm went up smoothly with a good response and fell back the same. No sign of any hesitancy or stumble.
After about 4 minutes ( O2 sensor kicking in) the rpm dropped to about 1050 (seems right). Still no idle stumble or hesitancy.
Left the bike on idle waiting for the fans to cut in (another ECU function). Yes they did, so off for a ride test.
Results have to be entirely subjective. I won't be able to feedback any change in gas consumption until I've run through a few full tanks. The first impression was at pull away the throttle control was perkier and more responsive. I noticed when shifting, the rpm didn't drop abruptly like it did before, making shifts a bit smoother. At cruising speeds and accelerating up from the 60's, performance seemed and sounded smoother and I didn't think I had lost anything.
After a 1/2 hour cruise and a hot engine I decelerated to a stop. The idle was rock steady with no hunting, hesitation or stumble. The muffler spout was grey to brown. I also think there may have been less smell from unburned gas after a cold start.
It's too early to give a total thumbs up to the 296 firmware in a K1200GT 166 ECU for a 1997 KRS, but I'm optimistic there are no downsides.
I will be watching for:
Fuel gauge low fuel light trigger point (may need diags re-calibration)
Winter cold start and running.
Thanks to Rick aka K-K and Bob RFW for 'contributions'.
I hope this helps out somebody with an older bike and a dead ECU, or somebody with a 'Stumbler'. Note that if you are looking for a boneyard 166 ECU, you should pay bottom dollar because there's too much written about throttle stumbling problems. When I got mine I noticed of all the K bike ECU's on offer, the 296 was ridiculously expensive and the 166 was often the cheapest.
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