stall issue resolved

[bgl]

Hello

 

For the sake of anyone else who may someday experience this difficult situation, my car developed a stall problem overnight--actually after having the oil changed on June 20.  There were no warning signs, nothing.  After paying for the oil change, I went out, and car would not run.  Did something happen in the shop? 

 

It took nearly 4 months and a total of 3 shops to resolve it.  Initial diagnostics were not exact as non-defective parts were replaced such as the air idle control motor, ignition control module, and crankshaft position sensor.  After that, at the last shop, the screening involved intensive testing over several days.  It was found that there were no bad cables or connections and no bad air flow sensor.  And, the already replaced items appeared ok and could be ruled out. 

 

Apparently moving up the electrical feed line, it turned out to be the ECM.  Replaced the ECM.  Problem solved. 

 

Well, not so fast.  Car was ready to go and all of a sudden, when I came to pick it up, error codes came up.  Upon more testing, the new (remanufactured) ECM was defective.  Had to get another, replace, and test again.  It is now home in my garage.  Almost scared to drive it.  What next?   

 

Not sure how much this will all cost, but it was plenty and I don't even have the bill from the last shop yet.  It's a small concern compared to a stalling car though.   

 

This may not be of much help, as many things can cause stalls.  But, if it helps one person, it is worth writing about. 

 

Bye! 

[waltmail]

Uh oh. Hopefully that remanufacturer of the ECM is reliable. There is one major supplier in South Florida who is a huge internet presence and claims to sell reliable rebuilt ECMs for all vehicles. His products, generally are trash. Maybe Jim Finn has used reliable units. Best wishes to you.

[Barney Eaton]

BBA Reman in Taunton MA rebuilds and warranties all sorts of automotive electronics.   I called them 3-4 years back about Reatta instrument panels and they will do 1990 and newer.  Several Reatta owners have used them and I don't remember if I ask but they will probably do ECM and BCM as well as the ABS controller.   Their web site is www.bba-reman.com and phone number is 866-573-2740

I recall one Reatta owner saying the did the IP for $100

[ChrisWhewell]

On October 12, 2016 at 9:32 PM, bgl said:

 

 

Well, not so fast.  Car was ready to go and all of a sudden, when I came to pick it up, error codes came up.  Upon more testing, the new (remanufactured) ECM was defective.  Had to get another, replace, and test again.  It is now home in my garage.  Almost scared to drive it.  What next?   

 

 

 

Thanks for that.   Your is not the first account of a remanufactured ECM being defective, that's why I waited so long before replacing mine.  In fact, I replaced mine with one from a parts car I bought, instead of a "new" remanufactured one from the web site stores of today.   What sucks is that all these companies and industries are keeping on, allgedly, improving quality while in reality they're just trying to cut costs.  Sometimes I think a used ECM might be better than a new "remanufactured" one. 

 

One thing I notice, is that the Reatta electronics operate via "switched grounds", yet the chassis of the ECM is not grounded. That's kind of weird, I'm not sure why, it just feels weird.   I bet the switched grounds aspect of these cars has something to do with the electronics failures, static charges building up, etc.   Would it be wise to ground the chassis' of the various modules to vehicle ground to prevent static build up ?   I think static is what causes stuff to fry.    I don't know....   What if I ground my ECM chassis to the vehicle frame ??

[Digger914]

2 hours ago, ChrisWhewell said:

One thing I notice, is that the Reatta electronics operate via "switched grounds", yet the chassis of the ECM is not grounded. That's kind of weird, I'm not sure why, it just feels weird.   I bet the switched grounds aspect of these cars has something to do with the electronics failures, static charges building up, etc.   Would it be wise to ground the chassis' of the various modules to vehicle ground to prevent static build up ?   I think static is what causes stuff to fry.    I don't know....   What if I ground my ECM chassis to the vehicle frame ??

 

This isn't the only car that GM built with isolated ground ECM's and GM didn't needlessly spend an extra buck on every car they built.  Grounding to the chassis would be about as wise as replacing a good fuse with a paperclip,  it's not a problem until you have a problem, then your little problem becomes a big problem.

 

 

[ChrisWhewell]

1 hour ago, Digger914 said:

 

 Grounding to the chassis would be about as wise as replacing a good fuse with a paperclip,  it's not a problem until you have a problem, then your little problem becomes a big problem.

 

 

 

Maybe the ungrounded chassis of the ECM acts as a big capacitor plate around all those sensitive democrat electronics, and builds up static, which then intermittently discharges when conditions of moisture, etc. are the perfect storm, and it zaps stuff to a sub-clinical level.  I don't know... I'm not wise, just old    Maybe I can hang a copper wire off my bumper to scrape the pavement as I drive to keep static from building up....  

Edited October 15, 2016 by ChrisWhewell (see edit history)

[ChrisWhewell]

Like, make a Leyden jar and contact it to the ECM while driving about, day-to-day and observe the metal leaves to see the charge.   Here in Texas, beginning about November and running through April, something changes environmentally where, when I slide my chair around, I always get a shock when I touch the filing cabinet.   Come springtime it stops and doesn't come back until way late autumn.   An interesting research project for retired Reatta engineers might be to do a historical analysis of what time of year most ECM first failures occured.   I bet the result would show there is a seasonal correlation.

[Digger914]

These things read sensor signals in millivolts, the theory of isolated ground is to prevent noise and other spikes from getting in where they shouldn't. There is always a just in case circuit somewhere in the electronics that is supposed to provide protective discharge and you never really know if it's working like it's supposed to, until it doesn't. When the airbag doesn't blow, the computer doesn't fry and you think about the 101 things that are done to cars every day while pulling plugs, or hooking up jumper cables and all the bad things that could happen that don't, you have to appreciate that these circuits are pretty reliable.

 

The unwritten rule of electronics stuff is that if it doesn't break in the first 90 days, it will probably last forever. Could static electricity cause odd problems and even kill the ECM, heck yes. Does the ungrounded ECM chassis act as a big capacitor plate which intermittently discharges when conditions of moisture, etc. are the perfect storm, not supposed to, but not theoretically impossible. I would look for a flakey diode in the alternator to fry one of these long before I would even consider this as a possibility. 

[ChrisWhewell]

Whoever wrote the 90 day rule was on crack, few light bulbs fail within 90 days, same with water heater elements, etc.   My buicks that are negative ground never suffered any ECM weird stuff happening, the switched ground automotive electronics experiment was a failure, else they'd still be doing it on some vehicles.  I wonder who's idea that was and what their justification for switched grounds was.  I'd wager if one researched all the cars that ever had a switched ground system, where the chassis on the ECM was isolated from ground, the results would show such vehicles have many more electronics failures than vehicles with switched hots.   viz, all my other cars including two Rivieras that never had any ECM trouble, 200k miles each, also evidencing that Buick itself abandoned switched grounds, its just weird.

[ChrisWhewell]

I'm not complaining really, just trying to figure out.... maybe... the root cause of some issues.   I notice the ECM is mounted to the vehicle using plastic (insulative) hardware and yes it would be foolish to ground the ECM chassis to vehicle ground.   But, would maybe connecting it to bat + terminal be a bad idea ?   Not a direct connection to bat + , rather, a circuit that permits small amounts of excess charge to be bled off.   I'm sensing with the Reatta's switched grounds system, there's a whole bunch of stray capacitances all around the vehicle.   I'm just trying to get to why my other vehicles never had ECM , etc. problems, yet the Reatta seems to.  So far, I'm really sold on the idea of static build up as the root cause of so many ECM, BCM and climate module's quirky failures.

[ChrisWhewell]

Would there be any benefit perhaps, to connecting all the chassis of the ECM, BCM and Climate module to one another by a bus wire, to keep these 3 chasis' all at the same potential ??

[Ronnie]

14 hours ago, ChrisWhewell said:

 I wonder who's idea that was and what their justification for switched grounds was.  

 

I'm not an electronics person when it comes to their design but I asked your question to a friend of mine who works on MRI machine electronics. He put together all the electronics on his Cobra kit car so he knows about automotive electronics as well. He is pretty sharp. Although he doesn't know why GM switched the ground circuits instead of the hot, he said one possibility is preventing damage to electrical components like the ECM if the battery is connected backwards. The way I understand it is if the ground circuit is normally open and you connect the positive side of the battery to that circuit, there isn't a path for the positive voltage to flow into the component to fry it. Just something to think about.

 

About isolated grounds:

Several electronic components on the Reatta, including the ECM, need pure DC to operate properly. They use isolated ground connections that give a direct path to battery ground to provide a noise-free ground return path separate from the equipment connected to chassis ground - such as the alternator (it produces AC before going through the rectifier) and other devices that are connected to chassis ground.  The isolated grounds go to a terminal block behind the battery and then directly to the battery bypassing chassis ground. It is important to keep those connections clean and tight to prevent problems with the electronics on the Reatta.

[ChrisWhewell]

Thanks for that, sir.   Very interesting.   I've read also about voltage spike absorbers, maybe the answer is to just put one of those on the alternator output.   There's definitely some aspect that makes the electronics prone to earlier failure, all I can think of is voltage spikes at the alternator output, or static build up.

[Digger914]

1 hour ago, ChrisWhewell said:

But, would maybe connecting it to bat + terminal be a bad idea ?   Not a direct connection to bat + , rather, a circuit that permits small amounts of excess charge to be bled off.   I'm sensing with the Reatta's switched grounds system, there's a whole bunch of stray capacitances all around the vehicle.   -------.  So far, I'm really sold on the idea of static build up as the root cause of so many ECM, BCM and climate module's quirky failures.

 

I've never cut an ECM open to look inside,  but I have cut open several different GM climate control modules and I expect that what you are describing here is already a part of the circuit design. As said before; you never really know if it's working like it's supposed to, until it doesn't. Best example is the good old picture tube TV. The high voltage supply has a bleed circuit that works well until it doesn't and you find out it's not working like it's supposed to after you turn the set off, unplug it from the wall, take the back off and stick your hand inside. This nasty zap doesn't come from static, it comes from capacitance that wasn't bled off when it should have been.

 

Isolated ground and switched ground are two different animals. Isolated ground can also be described as floating ground and all three of these modules come together at the diagnostic center where they all connect. Twenty five years ago GM used technology of the time to build something ahead of its time into the dash of the Reatta. In todays CAN system everything is designed to ride the same buss and bad buss connects are a real pain. After twenty five years of bouncing down the road who knows what might not be connecting, or working like it should. 

 

Bussing these three module chassis together could be the logical solution to a lot of problems; then again, the picture of a tree with swing and the question can bumble bees fly comes to mind. What's designed on the drawing board is built on the bench and by the time the bugs are worked out, there can be a real difference between the working thing and the mathematical model of the thing. My guess is that switched ground was used instead of a debouncing circuits because of manufacturing cost and that it was abandoned because it didn't work as well in practice as it did on paper.

 

If the cure is the same, it really won't matter if the capacitance zap comes from static or a bad pin head sized bleed capacitor buried under a half inch of potting compound. There could also be a very good reason why the people who made this system work didn't buss these chassis together and you might want to stock up on spare parts before you try this. 

 

 

[padgett]

If you really want to fry electronics, start at a high idle with the alternator at full output and disconnect the battery. I have seen surges over 200v in the system as the alternator tries to push (pull ?) electrons everywhere. (ELI the ICE man).

 

GM has been making electronic ignitions since the early '60s and have always been very reliable.

 

However, infant mortality is just the front half of the bathtub curve.