b556 code

[skidd1000]

First off thank you to this forum for all the help on my 91 reatta. No more check engine light. I do still have a bcm code of 556 (eprom fail). There is a error message where the odometer is supposed to read. Before I dig into the dash and find the bcm, is there anything else that I should be looking for? Also there is a sir code of 061 but I think that is from a burnt out dash light.

[KDirk]

That 556 code is usually because the BCM EEPROM which contains the odometer, vin and option content has been corrupted and can no longer be read by the BCM. Thus the odometer is not displayed and no further mileage is accrued until a good EEPROM is installed in the BCM. Can probably get a GM dealer to send it out and program it still, though that service is getting difficult to find anymore for cars of this vintage. I can be of assistance, if you are so inclined you can PM me here for details. 

 

 

Edited May 11, 2018 by KDirk (see edit history)

[padgett]

AFAIR the EEPROM is a 2816 and pretty easy to clone from a good one. Doubt that 88-91 is the same and I only have earlier ones.

 

First thing I would try is to just R&R the chip (is the smaller one). Disconnect the battery first and see if it clears.

[skidd1000]

Pm sent kdirk. Thanks padgett, I will try that since it needs to come out either way. Is the dealer able to clone a new chip if this does not fix it?

[Chellica]

Hi guys I am also having the B556/bad EPROM odometer error. I tried swapping a working BCM from a 92 Olds Toronado which displayed mileage just fine prior to the swap to the Reatta (91), but it didn't work in the Reatta.  I couldn't switch just the PROMS as they have different connections.  I tried replacing the PCU, but that didn't fix the Odometer error.  Does anyone know of any place that sells just the PROMS?  Or any other ideas for a fix?  I will also try calling around to different GM dealers, but I doubt any in my area (Minneapolis) are going to be able to reprogram them.

[2seater]

27 minutes ago, Chellica said:

Hi guys I am also having the B556/bad EPROM odometer error. I tried swapping a working BCM from a 92 Olds Toronado which displayed mileage just fine prior to the swap to the Reatta (91), but it didn't work in the Reatta.  I couldn't switch just the PROMS as they have different connections.  I tried replacing the PCU, but that didn't fix the Odometer error.  Does anyone know of any place that sells just the PROMS?  Or any other ideas for a fix?  I will also try calling around to different GM dealers, but I doubt any in my area (Minneapolis) are going to be able to reprogram them.

I suspect you will need a junkyard replacement BCM with the Prom from a 1991 Reatta. Is the BCM good and just needs the PROM? A replacement PROM will display the donors mileage and information.

[Chellica]

I’m not sure if anything is wrong with the BCM itself or if it is just the PROM. In addition to the odometer error, the headlights don’t pop up automatically from the twilight sentinel and the warning chime that the fog lamps were left on after the key is pulled out doesn’t work. Would those indicate a bad BCM in addition to just the PROM? The cd player doesn’t work (I don’t think is related). Otherwise all other functions work (including headlights left on chime) and the car drives fine.

[2seater]

Unfortunately, the other items are an unknown. I have been looking at the "E" body parts book for Buick so I cannot tell in the Olds part bears any relation to the Buick. The BCM number listed, 16137994, is listed as a remanufactured controller. There is also a part listed as the calibrator memory for BCM, 16155458. I don't know where that might lead at this point.

Edited April 4, 2023 by 2seater (see edit history)

[Ronnie]

1 hour ago, Chellica said:

I tried replacing the PCU, but that didn't fix the Odometer error.  Does anyone know of any place that sells just the PROMS?  Or any other ideas for a fix?  

I think from what I read in the 1991 service manual (below) that you will have to find a BCM that your PROM will plug in to. Notice that it says the PROM cannot be moved from one vehicle to another without getting the odometer ERROR displayed. Oddly enough, Rockauto lists BCMs for the '90 model but not for the '91 model. That makes me believe the '91 BCM is unique to that model year. Good luck on finding one at a dealership or getting a BCM PROM programmed just for your car.

 

[Chellica]

Interestingly, the part # matches for both BCMs: 16137944. I am in contact with Prospeedo about obtaining a new EEPROM. 

[padgett]

OK, the BCM itself is common to several vehicles, the UVPROM (27(h)c256 is specific to themake/model. The EEprom 2816 is specific to the vehicle and contains the VIN and ODO (plus other settings) it has a checksum so cannot just reprogram.

 

Our vendors probably have a working BCM for your Reatta, will run fine, just have the rong VIN.