Speedometer not working

That looks like a 1991 BCM I believe.

No special way to distinguish the BCMs other than having someone who has an '88 Reatta to pull one from.

We have a couple in stock. The come without the prom and you just swap yours in. Give me a call if you'd like to order.

That looks like a 1991 BCM I believe.

No special way to distinguish the BCMs other than having someone who has an '88 Reatta to pull one from.

We have a couple in stock. The come without the prom and you just swap yours in. Give me a call if you'd like to order.

Unfortunately the prom is exactly what I need.

Easiest way I know is by the color coding of the connectors. 88 is black/black/red. Part numbers can be used if you have a cross reference (I don't have) but aftermarket remans (non-delco) will frequently not have any part number that traces back to GM. Note that there may be more than one valid part number for a given year.

Anyway, interesting that you apparently have a 91 bcm there. I've not had the BCM out of either of my 91's yet so don't know exactly what it - or the proms inside - looks like. Will find out soon enough as I will be dumping (copying) the PROMS for archival and to be sure I have a usable image to burn if I ever have a PROM failure myself.

My offer to make an 88 BCM PROM stands, if you are unable to source a correct one elsewhere.

KDirk

Well let me try and get the vendor to send me the right one. If I am unsuccessful I will definitely pm you.

Post #9 in this thread:

http://forums.aaca.org/f116/prom-codes-documentation-project-377091.html

shows that the part # for the BCM used in the 88s was unique. The 89/90 had a different one and the 91s a third.

So you need to find a BCM from an 86 to 88 vintage GM V6 car.

Standard motor products PN was EM7333. Used in:

BUICK REATTA 1988

BUICK RIVIERA (1986 - 1988)

CADILLAC ELDORADO (1986 - 1988)

CADILLAC SEVILLE (1986 - 1988)

OLDSMOBILE TORONADO (1986 - 1988)

One is available reman from RockAuto.

Only way I know to the sure is to pull the square plate and look at the four letter code on the PROM. Should be AMTR or AKTH for an 88. Do know that the wrong PROM can screw up the speedo in an 88 also know 88 is slightly different from later ones.(see below - BCM is on left).

Over the past two days I've been on the phone with Roger from Reattas.com who has been an immense help. Using some known working BC she went around moving them between years to are the effects. As we thought, the BCM from an 89 causes for the speedometer to read 0 constantly. Roger was able to reproduce the same problem on his own 88. Roger has been an enormous help and has gone above and beyond what any vendor I have ever met. I would highly recommend ordering parts from him in the future! Now all I have to do is receive the correct bcm and my Reatta should be in working order.I'll keep you posted.

Have you located the parts you need? If not, I have 1227333 with AMTR PROM installed.

Yes I have it on the way already thank you.

That new 88 bcm with an 88 BC did the trick! The speedometer is back to working order once more and I can finally do the state inspection! Thank you so much to everyone that helped and a special shout out to roger from Reattas.com who really went above and beyond to help me! I hope this thread can help people that run into the same problem as me!

I assume you now have a prom that has the wrong mileage and VIN? Might be a problem if you decide to sell the car. Maybe not depending on the buyer.

Ronnie,

Hopefully he is using just the new EPROM (one E) and is reusing the EEPROM (two E's) that was already in his car's BCM (presumed by me to be correct to begin with) as the latter holds the odometer and VIN along with all data specific tothat particular car. The other chip is the same accross all 1988 Reattas built and just contains the core program common to all Reattae of that year. So, no harm in using that one.

I would stress however that if the entire BCM with both chips from another 88 Reatta was swapped in, then yes the mileage and VIN will reflect those of the donor car. That is clearly a problem that could affect resale and eveyntuall show up in state dmv and carfax records as an odometer discrepancy.

As a side note, this episode is a good example of why swapping modules in these cars can be very problematic if the PROMS from the car's original BCM are not transferred to a replacement unit taken from another vehicle. Cars now have more sophisticated safe guards in place to prevent swapping modules that could go undetected. Almost all current cars have their respective VINS encoded in all major modules, and this is checked by the main controller (varies by make/model) to verify no improper modules are installed. Dealer reprogrammming is typically required to get past this, further reducing the opportunity for fraud, whether intentional or not.

KDirk

What's a BC?

I put in a whole new working bcm and will move the eeprom from the old bcm. It is good though that it gets mentioned here. It is unfortunate that these modules can be swapped so easily by a mechanic that didn't do their homework.

The only thing I wanna do now is replace the sparkplugs and wires, though I'm not sure where to start with those haha. There are so many differences in vehicles! My mom bought a used land rover and wow, I don't even know where to start with that one haha.

happy that you seem to have got the speedo, etc. working.:cool:

when you're ready to do the plugs/wires, you may want to start another thread. the front (of car) p/w's aren't that bad at all. the rear ones - not so much fun, but doable.

i'm sure you'll get several here to chime in with "easy tricks" for the rears. plus recommendations on what spark plugs and wires to use.

What's a BC?

i believe it's a type of powder used mainly by southern U.S. folks trying to rid of headaches caused by continually repairing their vehicles!!! :rolleyes:

Hey Kerry, the rear plugs aren't so bad. If this 61 year old with half a heart and a bad shoulder could do it, it can't be that hard.