vehicle computer communication problem detected.

[handmedownreatta]

my car went from running great to barely running in a moment driving home from work today.these are the codes im getting.

b132 oil pressure sender

b334 loss of ecm data

b552 bcm memory reset indicator

c553 crtc memory reset indicator

any ideas?i researched on ronnies site but unless the bcm has gone bad i don't know whats wrong.

[handmedownreatta]

advance auto has a body control module made by BWD.is this what i need?

[Rawja]

I'd take a quick look at your battery cables, particularly the positive cable which can corrode internally. Give both the positive and negative cables a wiggle while the car is running and see if you can reproduce the problem.

[Guest Mc_Reatta]

If you don't find an issue with the battery cables, also check and clean positive and negative connection points under the hood. This sounds like an loss of power problem from a bad connection issue not a bad module.

See the connection points here:

Negative Junction Box Location - ReattaOwner.com

[handmedownreatta]

i disassembled the three negative grounds per mcreatta.they looked relatively shiney so i put them back together.now the car runs like crap when first started for five seconds then smooths out.no more codes.i guess i'll pull the wires back apart tomorrow plus the positives and sand them.the only thing that worries me was it was 93 degrees when it screwed up so im afraid it may be a part getting too hot.it there something to put on the connections to protect them?thanks.

[Rawja]

The thing with the positive cable is that the copper within the cable can corrode where it meets up with the battery connection. This is not visually apparent as the corrosion is within the cable itself and hidden by the insulation. If you move the cable around near this connection (assuming the battery connection is properly-tight) and the car starts stumbling or if the cable feels "crunchy" internally or less solid than it feels further away from the battery, that's likely the problem assuming your grounds are good.

I went through this with my old '89, went nuts tracking other items down to no avail, when I discovered this was the problem it was fixed by simply skinning the wire further down to where the copper was good and installed a new battery connector which solved all the intermittent weirdness I was experiencing.

[handmedownreatta]

it wouldn't start at all this morning and the message is back.i'll pull the wires back apart today and look closer at them.

[handmedownreatta]

i pulled four ground locations apart and cleaned them plus the positive junction behind the washer bottle.i still have the problem.i have the same voltage at the positive junction and battery.i looked at the battery cables but i don't see anything wrong with them.im still getting the same codes.any other ideas?

[Guest Mc_Reatta]

I assume your engine is cranking but not starting.

Just looking at B132 indicates a problem with the oil pressure sensor or the BCM. Other codes could be explained by a faulty BCM, but I didn't think the BCM would prevent the engine from running, but the fact the fuel pump needs a signal from the oil pressure sensor may be why the engine doesn't run.

Try hooking up a jumper wire from the 12 volt terminal of the battery to the green fuel pump primer connector over by the brake master cylinder to run the pump and then see if the car will start and run.

If so then need to look at oil pressure to see what it's reading. You can rig a jumper across the oil sensor connector to determine whether it or the BCM or wiring is bad. See test on page 8D2-29 of the 89 FSM in the section on BCM trouble code diagnosis.

[handmedownreatta]

it seems to be an intermittiat problem.i was still looking at it.i turned on the ignition but not the starter.i got the same message with a flashing check engine light.just for the heck of it i tried cranking it again.the third time it cranked up and ran with no codes,i recranked it two more times and it acted normal.now im afraid to drive it anywhere.

[Ronnie]

it seems to be an intermittiat problem.i was still looking at it.i turned on the ignition but not the starter.i got the same message with a flashing check engine light.just for the heck of it i tried cranking it again.the third time it cranked up and ran with no codes,i recranked it two more times and it acted normal.now im afraid to drive it anywhere.

Most of the things that will keep the engine from running don't set a code. It's hard to pin the engine not running to a trouble code or check engine light being on. Example: low (or no) fuel pressure, bad ignition module, bad crank sensor, and a lot of other things, don't set a code. When an engine won't run at all you should always go back to the basic "engine won't start" procedure to find the problem. Spark, fuel pressure, and injectors opening are the first things to check.

[handmedownreatta]

i took it out for a test drive and barely made it back.two things i noticed.the onscreen tach stayed at zero and the temp stayed at cold eventhough i drove about five miles.the oil pressure guage seemed to work.

[KDirk]

Handmedown-

I had loss of tach/temp gauges on my 88 when I went through the episode with bad MEM-CAL inside the ECM. Also got the comm problem detected message a lot intermittently. You may want to pull down your ECM from behind the glovebox and make sure the MEM-CAL (long plastic module with light blue rectangular cover) is fully and tightly seated. Then, if that doesn't change it, manipulate the wiring on each of the three large connectors. There are a lot of discrete signal line in and out of the ECM and they are sometimes subject to not making if the car has been worked on extensively and the connectors are worn or loose. I don't know the history of you car of course, but worth looking at.

Finally, might see about getting a spare ECM (will usually need to swap in the MEM-CAL from your existing ECM) and see if that makes any difference. Bad solder joints inside the ECM can easily cause the problems you are getting. If you buy a rebuilt ECM from an auto parts store, be forewarned they are often not 100% right (like many "rebuilt" parts) as I went through 3 rebuilds before I got one that worked consistently. Each of the bad ones exhibited slightly different failure characteristics.

If you end up narrowing it down to a bad MEM-CAL (not terribly likely), you will need to find one for a 1989 Reatta specifically. 1988 is not 100% compatible, and not sure if 1990 will interchange or not, I do know 1991 will not work in any of the 3 earlier years. I know this gave me fits, and while you may have a different cause than I had, much of what you are going through is the same as what I battled with on the 88.

KDirk

[handmedownreatta]

thanks kdirk.i was out of ideas.i had a 280zx i had to wiggle the wires on.are both the ecm and bcm in the same area?

[KDirk]

Yes, the ECM and BCM are up inside the dash behind the glove box. They are a tight fit to get out, and you will need to remove the lower hush panel on the passenger side (black plastic piece under the dash to the firewall) and the glove box assembly itself. Then, you need to undo a couple of speed nut fasteners that hold the module mounting brackets in place. With enough patience and coaxing, both can be dropped down and onto the passenger floor pan.

Probably premature to say this, but if you end up needing a new MEM-CAL and have a hard time finding one, I could probably repair one for you, including burning a new PROM (chip inside the MEM-CAL) if need be. I modded the MEM-CAL in my 88 to place a socket for the PROM inside the MEM-CAL so that I could change it more easily in the future if I wanted to mod the cooling fan set points or other performance parameters. As the part comes from the factory, the PROM is soldered into the MEM-CAL. Extracting the old PROM chip for reading/reprogramming is a very delicate job, as is soldering in a socket to accommodate the new PROM.

I realize GM wasn't aiming for easy DIY service on this part, but the internal design really sucks to be honest. It certainly doesn't make it easy on tuners who like to tweak fuel maps and shift points, but that is not really germane to the the discussion at hand.

KDirk

[Guest Mc_Reatta]

What does your battery voltage read?

Does your odometer seem to be working OK?

[handmedownreatta]

the battery voltage was a half volt down from what my voltmeter said my battery was.the odometer is working and the trip odometer is working.

[DAVES89]

I think we are overthinking this. I would check the connections at the alternator and if it is good have the alternator checked. Then I would have the battery checked before I started looking at the BCM, etc...

If you have an intermittant charge from the alternator to the battery you could have many of the problems described...

[handmedownreatta]

the onscreen voltmeter says 14.1 volts while its barely running.its on the back burner.im putting my camaro back together to have something to drive.i had started a valve seal replacement.

[handmedownreatta]

ok.since my battery has top and side posts i ran a second battery cable from the battery to the red junction box.no difference.so i took that cable and tried the same thing on the negative side.no difference.so i unplugged and replugged the connectors for the bcm and the ecm seperately.no difference.so i removed both boxes and looked inside.nothing looked burnt.so i pulled the chips out and reinstalled them and plugged the boxes back in.no difference.where can i get these boxes checked?btw the ecm was a remanufactured ac delco.another thing i noticed was with the key on but not running i get a low oil pressure warning.

Edited June 24, 2012 by handmedownreatta (see edit history)

[KDirk]

Not sure if there are places that offer testing of ECM/BCM modules or not, as it would require very specialized equipment to run these through their paces (testing all inputs/outputs for correct operation/response). The easiest way to handle this would be to find a salvage yard with a same-year Reatta, Riviera, or Toronado, get the modules from that car then swap in the chips. Or get spares from one of the parts vendors on here.

KDirk

[Guest Mc_Reatta]

You've got an issue which is not easy to diagnose and can get very expensive to take the easy way and just start replacing modules.

As KDirk mentions, there is no place you can take your modules and have them tested. You need access to another car that you can swap modules in and out of to see which one is the culprit.

Getting used or even rebuilt untested modules can be a crap shoot as the replacement module can very likely have the same or another problem that will just add more confusion to the troubleshooting process.

Given your symptoms, I hesitate to even venture a guess as to whether you definitely have an ECM or BCM problem. The fact you have multiple memory reset errors definitely indicates you had a power issue supplying 12 volts to these modules. This usually is a battery (or charging) problem or connection issue which is why we recommended you look at those first. Those codes could remain as history codes back from the last time the battery was disconnected if never cleared so they may mean nothing now. They also can be set if one of the modules fails in such a way as to drag down the voltage of the power supply line or data line enough to affect the other modules.

We can try to use your symptoms to narrow down the likelihood that either the ECM or BCM is at fault, but in your case these are confusing. The engine should run fine without the BCM so the fact the engine stalls would lean me towards the ECM, but the oil pressure BCM error code you have is a BCM or oil pressure sender problem not related to the ECM, but as the oil sender also powers the fuel pump, could this be the issue that has your car running poorly and stalling. That's why I recommend you power the fuel pump directly from the battery and seeing if you still have drive ability issues. If so I'd bet on the ECM, if not then the BCM or oil pressure sender.

As your problem is intermittent it just makes it harder to track down. Other things to look at are the displays that need both the ECM and BCM to communicate like the speedometer, odometer tach and temp sensor, and others that only need one or the other like oil pressure. Also issues with getting into diagnostics mode or seeing data inputs to the ECM and BCM could give some insight.

You need to decide if your more interested in saving time or money to solve this problem. Obviously the quick way is to get a tested replacement ECM or BCM and swap it out and see what happens. If that doesn't work do the other. You'll now be out some money but hopefully have it fixed. If not, your back to looking at power supply problems or sensor and wiring problems. Or you work thru a lot of steps to figure out what the problem is and then replace it. That can be very frustrating and time consuming with an intermittent problem to say the least.

We will continue to try to help you every way we know how. Adding to the knowledge base of how our cars fail and how to repair them is crucial to all of us.

[handmedownreatta]

when i disconnect the battery does it clear the codes?btw my coil pack is leaking.could that be part of the problem?

Edited June 24, 2012 by handmedownreatta (see edit history)

[Ronnie]

when i disconnect the battery does it clear the codes?btw my coil pack is leaking.could that be part of the problem?

Yes codes are cleared by removing the battery cable. For your other question... it was covered in post #11 in this thread:

Originally Posted by handmedownreatta

it seems to be an intermittiat problem.i was still looking at it.i turned on the ignition but not the starter.i got the same message with a flashing check engine light.just for the heck of it i tried cranking it again.the third time it cranked up and ran with no codes,i recranked it two more times and it acted normal.now im afraid to drive it anywhere.

Most of the things that will keep the engine from running don't set a code. It's hard to pin the engine not running to a trouble code or check engine light being on. Example: low (or no) fuel pressure, bad ignition module, bad crank sensor, and a lot of other things, don't set a code. When an engine won't run at all you should always go back to the basic "engine won't start" procedure to find the problem. Spark, fuel pressure, and injectors opening are the first things to check.

[handmedownreatta]

Handmedown-

Finally, might see about getting a spare ECM (will usually need to swap in the MEM-CAL from your existing ECM) and see if that makes any difference. Bad solder joints inside the ECM can easily cause the problems you are getting. If you buy a rebuilt ECM from an auto parts store, be forewarned they are often not 100% right (like many "rebuilt" parts) as I went through 3 rebuilds before I got one that worked consistently. Each of the bad ones exhibited slightly different failure characteristics.

KDirk

i talked to a buick mechanic.he said the way they check modules is tap them while the car is running.i tried this and everytime id tap the ecm the engine would stumble.i ordered a new ecm.

[KDirk]

Handmedown-

Ok, now it sounds like you are getting somewhere. Keep in mind that the ECM is comprised of two parts: the ECM itself and the MEM-CAL (or chip if you prefer) installed within it. It is more likely the ECM itself would be faulty, but until you install your replacement ECM you won't know for sure if it is the problem or if the MEM-CAL is. I'll make the educated guess that you have bad solder joints within the ECM causing intermittent problems. There doesn't need to be visible (i.e. burnt components) damage to cause the symptoms you are getting.

As soon as you get the new ECM (with your existing MEM-CAL) installed, post back with your findings. I'll be interested to find out what happens.

KDirk

[handmedownreatta]

it seems to be cured.thanks for the help.

[ssmithmiami]

I am having many of the same issues with my 89. The odometer doesn't work, the speedometer jumps all over the place (I have replaced the VSS), the tach and temperature readings are intermittent and the engine sometimes gets above normal operating temperature. There is a "computer communication problem", and the service engine soon light stays on, but otherwise the engine runs great. According to the 89 service manual when you get "Low Oil Pressure" followed by "Electrical Problem", that sets the B334 code: Loss of ECM communication. I have yet to open everything behind the glove box to tap the modules and checks the connections, but in case I need to get a replacement ECM, where did you order yours? And did the replacement resolve everything?

[Guest Mc_Reatta]

Rebuilt ones are available at most FLAPS. There are of course the vendors on site, and most salvage yards will have used ones too since they were used in so many GM cars of the era. Should cure all ills, but frequently used replacements as well as rebuilt ones will not be 100% and same or another issue may show up. Make sure you can return anyone you get till you get a fully functional one. They are complicated modules and not easy to test outside of installing in a vehicle to see what happens.