BCM

[Guest SwiftBuicks]

O.K. I found a number of posts on this forum that related to a guy who was trying to restore his Cruise Control. He eventually found replacing the BCM, the solution. This time around, I am going to try the Junk Yards for a replacement. Of course this means rubbing shoulders with some rather interesting characters, but I definitely want not to be distracted. However, is there a source of new ones somewhere?

[dship]

The BCM handles alot more than just the cruise control. You might get deeper than you expect when replacing it just due to cruise control. And what's the problem with junk yard folks...they tend to have a wealth of car knowledge...might find them very informative if one takes the time to talk to them.

[D-a-n-i-e-l]

BCM can be bought new from most part stores, but i would find a used one first. Remember either way you must swap out the proms. I also agree with DShip, there are better places to start with.

[padgett]

Most common cause of cruise control failure is the brake switch. Next is the servo. Why do you think it is a BCM problem ?

[Guest SwiftBuicks]

There's nothing wrong with junk yard folks and don't think for a minute I have implied that. I started by replacing the vac hoses. Then I sanded the harness connections and sprayed them with WD-40. I put in a new brake light switch. (I had been driving without brake lights, I found.) Of course, the RESUME light remained on and there was no Cruise Control. I checked the hard button contacts. Then I replaced the Servo with a new one from AZ ($80 with core). No dice. Yesterday I bought some contact cleaner from Rat Shack. I'm going to go back over all the circuitry if I can next. However, now I only see one error code, B334, and the Computer Communication warning screen. I did locate the BCM and will clean the harness contacts again. Lasty, if you are interested, I found a long thread on this forum that followed a guy who went through all this. However, I have one CRT malfunction that leads me to the hope that the contact cleaner will restore everything. The tach usually doesn't work, but it has kicked in on a few occasions. This must be a bad electrical connection.

[DAVES89]

B334 code = loss of ECM data

Affects Cruise, A/C clutch,ECM service mode.

Because you got a warning on your touch screen or instrument cluster [can't remember which] regarding cruise control, I think that you are going down the right path thinking that it is an electrical connection in the cruise control.

BTW did you check for a crack on the big vaccum hose that goes from the servo to the fire wall? Mine was cracked and wouldn't allow the cruise to work. You didn't say but I think you might have changed only the small vaccum hoses. Also recheck your small tube tee for cracks as it is very brittle due to age.

However does your A/C clutch engage?

[padgett]

Is the RESUME light on all of the time, even when you have just started the car ? That would indicate a failure in the BCM. Have you followed the diagnostics in section 8A-34 of the FSM ? (page 8A-34-6 in the 89)

[Ronnie]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Of course, the RESUME light remained on</div></div>Just a little food for thought... what normally makes the RESUME light come on? Tapping the brake. It would seem logical that something is telling the BCM you have tapped the brake as soon as you try to engage the cruise. The BCM in turn would turn on the RESUME light immedeately. A defective switch or wiring could cause that.

[Guest SwiftBuicks]

Well, thanks there Ronnie. I had no real understanding as to what put the resume light on. >>It would seem logical that something is telling the BCM you have tapped the brake as soon as you try to engage the cruise.<< Actually, the Resume light goes on when the IP lights up and it stays on constantly. I did consider that it could be a bad circuit i.e. a fuse, fusable link or short. However, I am also getting the error code B334 and the <span style="font-weight: bold">COMPUTER COMMUNICATION PROBLEM DETECTED some vehicle function may exhibit degrading performance</span> screen message. That fits in with the lack cruise control, Tach or other vehicle function. <span style="font-weight: bold">Padgett</span>, >>Have you followed the diagnostics in section 8A-34 of the FSM ? (page 8A-34-6 in the 89)<< I haven't obtained an FSM, yet, and am still shopping for one. However, if you could scan that page and put it up or send it to me, I'ld be your cyberbuddy for life. >>Because you got a warning on your touch screen or instrument cluster [can't remember which] regarding cruise control, I think that you are going down the right path thinking that it is an electrical connection in the cruise control.<< Now, after replacing the Servo with a new one, I only get the Computer Communication warning screen. >>However does your A/C clutch engage?<< The A.C. has been automatically turned off because the freon is low. I see that screen once in a while, but haven't seen it recently. The B670 series error codes have disappeared, though, with the addition of the new servo so I assume that the BCM sensed it.

>>BTW did you check for a crack on the big vaccum hose that goes from the servo to the fire wall?<< I did check that hose on both sides of the firewall as I found it when replacing the brake light switch. It seemed o.k. to me. (Not that it has given me any expertise but I used to work in Boston Woven Hose, a division of American Biltrite. I was an agitator for the United Rubber Workers. ) >> Also recheck your small tube tee for cracks as it is very brittle due to age.<< I'll do that.

[Ronnie]

Sorry that i interrupted you chain of thought. It appears you have already thought of everything. Well, maybe not everything... Your cruise still doesn't work.

[padgett]

Not quite. When you start the car the SPEED value is clear. You must exceed 25 mph before the SPEED value can be set. This engages the cruise control if the brake loop is made.

Once engaged, tapping the brake disengages the CC, turns off the CRUISE indicator, and turns on the RESUME light. If an 88-89, you can see the cruise set speed on the SUMMARY display.

On all years, BI71, 75, 76, and 77 refer to different inputs from the cruise control devices, BD60 is the vehicle speed, and BD70 is the output to the cruise control servo but the latter only has relevance if in cruise.

One thing the general was good at was keeping the same input, output, and circuit designations across the years. Cruise Control will always be in section 8A-34.

This is why as you go through the 8A section there will be gaps such as 8A-92 (rear windshield wipers)for things not present in the E-body.

So if the RESUME light comes on as soon as you start the car, something is wrong and probably the BCM as noted.

[Guest SwiftBuicks]

Perhaps I have thought of everything, but have not gone through with the activity required. I tried finding the old thread for you guys. However, I haven't been able to do that. I did print out the messages, though. This poor soul (perhaps his Reatta made him poor) spent a considerable amount of time and money to finally restore the Cruise Control. He first put in a used BCM. Then he hired a guy who put in a new one and other parts. However, he wasn't getting the same error code. Whatever, I'm headed down to the garage now. I will report back later, hopefully with a clearer account. (I tried to see if my computer could run off of the Wi-Fi signal there, but it didn't.)

[Ronnie]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Re: cruise control

[Re: red head1228]

Member Registered: Wed Jul 30 2008

i just got it fixed 341.00 they had to put on a new bcm

</div></div>

[Guest SwiftBuicks]

Yes, a hefty charge to add to all the trouble previous. Whatever, I did another check of the car. The <span style="font-weight: bold">COMPUTER COMMUNICATION PROBLEM DETECTED some vehicle function may exhibit degrading performance</span> screen message still comes up from time to time. B334 is the only current code. There is NO ECM DATA. I'm going to make some calls and price a BCM.

>>On all years, BI71, 75, 76, and 77 refer to different inputs from the cruise control devices, BD60 is the vehicle speed, and BD70 is the output to the cruise control servo but the latter only has relevance if in cruise.<< Are you referring to the diagnostic codes? ECM, E60-E63, all involve the Cruise Control. Shouldn't I see at least one of them? I don't get anything from the ECM. Yesterday I went into Advanced Auto and priced a BCM. With the core they gave me a good price but couldn't locate one in their system. Today I'm going to try to call AZ and CarQueen.

[Guest SwiftBuicks]

Well, I didn't have the best experience chasing down a BCM yesterday. I called the AutoZone 12 miles from my garage. The guy said he had it in stock. I called the nearby AutoQuest. The guy requested the Delco number, 01228786. He couldn't locate a match. So I drove up to AZ to buy it. Unfortunately, the guy had an ECM which he said was a BCM. He came up with a Cardone_Reman number, 73-8786, and the picture matched. Nevertheless, AutoZone didn't have any BCM's listed in their system. However, since the guy was rather apologetic about his mistake, he called the Mom-and-Pop part's store up the street. With the Cardone number he had found for the part, the guy there told us he could get it for me this morning. Then I had him call CarQuest. They also had a match for the Cardone number, but wanted $20 more. The drive up and back runs $2. I went to the Mom&Pop store and told the guy that I'll be in on Monday to take it. This isn't the kind of run-around you'll find with junkyards, but it is similar.

[padgett]

BTW you can download the factory service manuals for 89 (works for 88), 90, and 91 from http://Reatta.net/docs.html

- you will need to register but much of what we are saying does not make sense without the manual. If you get one section first, you want 8A - Electrical.

Troubleshooting properly can save a lot of money over just throwing parts at it.

BTW I have seen a B334 when the battery is changed - was it Current or History ? And is the ALDL cover in place ?

[red head1228]

i went though the same drill i finally put a new bcm on problem solved i had used the one from my parts car and the cruise would work but threw a diffent code then i just about give up my bcm from a buick dealer cost about 130.00 i am happy now for awhile till the next thing comes up but oh well

[Guest SwiftBuicks]

O.K. I am going to go over all this in the morning, but this evening report is rather dismal. I didn't solve anything by putting in the new BCM. However, since the trouble codes remain the same, I don't see how the new module is any different than the old i.e. good. Now, the Resume light goes on when the doors are opened, not just when the car is started. It remains on constantly. B334 is my silent partner. It comes up frequently as the screen message >>COMPUTER COMMUNICATION PROBLEM DETECTED some vehicle function may exhibit degrading performance<<. I get NO ECM DATA, but have found out how to access the BD (Body Diagnostic) and BI (Body Instruments?) codes. What's C/C? I have replaced the Glove Box bulb and the underhood bulb with negative resultsi.e. they don't connect. The Tack still isn't showing. Then again the Electrical Problem light on the IPC seems to be suspiciously coming up at 25 m.p.h. Then again, I may be wrong. Nevertheless, I made a lot of new friends at the part's store, fooling them into thinking I knew what I was doing.

[padgett]

That sounds a lot like either the ECM or the BCM have the wrong PROM and you have a lot more rong than just the cruise control.

The ECM provides the engine data via the serial link (ALDL) to the BCM but it just shoves out the data points as a string of bytes, the BCM must know the order of the data it receives.

Get one wrong and it will try to read the rpm from the coolant temp byte.

[Guest SwiftBuicks]

NO, padgett, the car runs well with only a couple of electrical circuits that aren't complete. I suspected that it was a bad solder or two in the BCM. Now, I wonder if there's something like that in the ECM, but I'm not going to throw any more money at the problem until I've done the grundge work of checking the wiring circuits carefully. Today, I am going to go over the schematics in Hanes. I should have given more credence to Daniel and Dship and done this first. However, the BCM isn't hard to access as the ECM is. I met another knowledgeable mechanic, too. The trip to the part's store wasn't a waste of time. I am waiting for a reply e-mail from Reatta.net, now.

[Guest ekvh]

Let us know how it turns out, I have similar problems and haven't changed the BCM yet. I ran the suggested diagnostics from the FSM and it pointed me to BCM, but I haven't stood on my head and checked thoroughly the brake switches. I also think I'll find another C/control servo off a junker and try it before biting the bullet for a BCM.

[Guest SwiftBuicks]

Well, I have been going over the schematics, when the car comes back from Midas, I'll start working on the Cruise again.

[reattadudes]

Swift,

perhaps its time to throw in the towel, and take the your car to a shop that sepcializes in auto electrical work. they will have your problem figured out in no time at all.

I always tell my customers to skip the "fishing expedition", and let a professional figure the problem out. fishing expeditions can get very expensive, and also very frustrating. that PCM is no fun to remove, either.

case(s) in point: two 1990 Reattas here in Arizona.

car 1: problems: tachometer would not read over 900 RPM; temperature gauge non-operational; intermittent A/C problems, trip meter operation erratic.

car 2: problems: trip meter operation erratic, intermittent A/C problems, erratic tachometer operation.

did both have the same problems? nope.

car #1 had a bad PCM; car #2 had a bad BCM. I delivered both parts to both shops, and watched the results when they changed both units.

you have no way of knowing if the used units you are getting are good or bad (even reman units can be bad), or you could even have an issue with a PROM that has gone bad. your problem could also be a wiring issue, and have absolutely nothing to do with the BCM or PCM.

let a professional figure it out; your frustration level will drop dramatically.

Mike

buickreattaparts.com

[padgett]

I agree with Mike here, if you are competant then repairs are either easy or frustrating. The frustrating part is often not knowing if a part is good or bad.

This is where having two similar cars can help as can having known good spares. UPullit is having a 2fer1 sale so plan to acquire a couple of CC servos and Delco ignitions plus whatever else I spot that seems useful. Usually 50% will work and the rest always have some good parts.

Of course in central Florida, rust has to be imported.

Expect it won't be long before some of these parts get rare and ex$pen$ive.

[dship]

I've been following your frustration with cruise control. In reading through my 92 Riviera FSM, I believe cruise control is associated with the PCM, not the BCM. Granted, my FSM is not for an 89 Riv although I would think they'd be similar. If you end up having to swap out your PCM, don't forget to also swap out the prom board as D-a-n-i-e-l has advised us often. The prom is personal to your individual car.

[padgett]

91 is the only Reatta that used a PCM (Powertrain Control Module). That said the cruise control module (under the hood with bellows and all) is common to a large number of GM vehicles of the period and does not care where its control signals come from.

[Guest SwiftBuicks]

reattadudes, I have travelled the U.S. coast to coast more times in an auto than probably any other man. Over thirty times I have gone from the Appalachian mountains to the Rockies and many of the trips I drove. I've been all over Cali, all over Nevada, all over Utah, all over Colorado, driving. I have been to Santa Fe 7 times in my own car. Considering how I make my home in Eastern Ma. and have repeatedly travelled all the North Eastern states from Maryland and Penn. to Me., I feel this is extensive driving experience. Topping that off, I drove a taxi cab in Boston for 12 years. Never did I have the luxury of cruise control until my last few years with trips to N.H. and now Florida. This "problem" has been a challenging occupation for me. I don't need the C.C. I welcome help, but not that motivated by mechanics' pecuniary gain. I want to help other Classic Buick owners to learn how to fix their own vehicles and that is why I started this thread.

[dship]

Pagett...This is why I totally enjoy reading the forum. I learn new stuff everyday especially the querks of one year's car to the next.

SwiftBuicks...Don't give up on tackling your c/c problem. As you say, someone out there is going to benefit from your experience.

[Guest SwiftBuicks]

When it comes to the C/C, I'm starting to think that there's some kind of short in the wiring of the IPC that has shut it down. The Resume light goes on before the mileage light and after the courtesy lights when the thumb button on the door handles is depressed. The Resume light remains on during all operations of the car. The Electrical Problem light in the IPC goes on and off intermittently. I suspect that the malfunctioning resume light has nothing to do with the Computer Communications trouble, although it could. I also wonder if there may be a short in the wiring around the brake switch. I am going to recheck that, although I put a new switch in. When I put a new Servo in, the BCM error codes related to it disappeared. There must have been something wrong with the old one. The only possible mistake I have made so far would be putting in the new BCM. However, not only have I avoided paying the high wage rates demanded in this kind of work, I have educated myself in the make up of modern vehicles. It is like the time I took on sleepless nights taking apart old defunct personal computers and putting together one's that worked. I wasn't paid for them, I could have bought a better computer, but I now know something about computer hardware and how it is organized. Then again, this compares to all the hours I spent learning writing HTML for webpages that probably are never viewed and didn't bring me any income. I know how to write HTML and that gives me a definite advantage when surfing and using the web to gather information that aides me in my other tasks in life.