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 ??

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.

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.

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.

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....

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 ??

Haha, good one. A little humor is always a good thing !!

Center caps won't come off, if you synchronize them. You have to get all the R's to be pointing the same direction, such as all four of them in standard, upright position for the letter R. This prevents destructive interference from wobbling one or more of the caps off. Sometimes this means removing one or more of the wheels from a hub and locating it on the lug nuts right, so that the center cap can be installed with the R straight up. ok just kidding, gotcha

Will the PROM from a '91 fit into the ECM on a '90 Reatta and everything operate normally ? Maybe a little extra performance ?

Yeah, I hear ya. I sold my vette last week, and a 93 cutlass yesterday. I feel like a free man again, not chained to these machines !! Next to go is the HD Road King. Its a good thing you got the rodents out before they had a piss party

For posterity's sake, the solution to this was changing out the ECM. Note to self: If changing the ECM in the future, after unplugging the three connectors, move all three to the right as much as possible. Disconnect the antenna wire coupling and the white connector that is also in the way. Loosen and remove the 10mm bolt that is over to the left a little, that holds a wad of vacuum hoses in place. Remove floor mat. Remove the single torx fastener that holds the ECM in place and pull it out. When replacing, push the wire harness with the three connectors over to the right and out of the way. This is a 10 minute job.

Yep. And the trunk quit opening itself and door locks stopped actuating themselves on startup also, after ECM change. Don't ask.... but, my radio used to not put out sound until like 5 minutes after I'd turn it on, but now comes on instantly. So yeah, depending on how its screwed up, a bad ECM can make some strange things happen !!

I was bummed, my 16-way seat would not go down, only up, and my head was on the headliner already. No down control I learned, if you hold the non-functioning up/down knob on the door switch in the "dn" position, while simultaneously moving the "tilt" switch on the door to the left, you get a different result than had you only moved the tilt switch to the left without holding the non-fiunctioning "dn" knob to the dn position. In other words, holding the knob to dn and simultaneously pushing "tilt" on the door control to the left, the seat will go down and tilt at the same time. So, basically, hold knob to dn and tilt button to left. Then, tilt to the right for a little bit. Then hold knob to dn position again and tilt to the left some more, and the seat will be down again after a couple iterations of that. Hurray

Today, did an ECM swap, it fixed my intermittent dash display and importantly, made my AC work again. Since June 1, here's the list: AC orifice tube new AC drier AC charge AC relay ECM swap fixed antenna per Barney's method new front strut (Thanks RedSlate89) new axle shaft new radio fixed climate control per Barney's method replaced marred rim repaired center cap, epoxied medallion 16-way seats installed window tint repaired headlight switch (Thanks Jim Finn) new accessories belt installed camshaft magnet new transmission pan with drain new transmission filter new transmission fluid put an air cleaner in it new trunk latch solenoid new brake light bulbs redid most splices under the carpet

FIXED. The problem was the ECM. I pulled the ECM from my parts car, it has a sticker on it that says "GM Remanufactured", so obviously someone swapped it already on that car. Popped it into the '90 I like more, and voila. No more intermittent tach and temp gauge problem and the AC works fine. (lack of temp gauge was making AC clutch de-energize). Also, was previously unable to read any engine data when in diagnostic mode, so that's fixed also. Now to hit the highway, I bet the cruise control will also work, lets find out...

I had similar once, it turned out it was an open spark plug, and a bad wire, each on different cylinders but both failed at the same time

Yes, I'll hire this job out, I'd probably end up with the craters on the moon look, per the last post above by bikemikey. Maybe I can try to spray some electronics cleaner on the saggy portions so as to saturate them, then gently press them to the existing pad, under the theory the hexane in the electronic cleaner will re-soften the old adhesive enough to make it stick again. woudln't that be funny if it worked ? !!!!

Rebuilt my power antenna per the Eaton proprietary bulletproof method. Works good

Ok, I still have some of that from when I did my belt buckle, real silver solder, jeweler's grade from a little joint down on Burnet road. Thanks again

Wrapped up my front brake ABS sensor leads this a.m. Now I can run her through the touchless car wash....

Windshield ? Aren't they worth like $1400 ?? Also, how about the entire braking system....

I hear ya Barney, I'm the same way. But also, sometimes.... I've saved so much $$ by doing so much on my own, that I can afford to spend a little having a professional do something. Like the time I tried putting window tint on a car....twice.... it ended up badly so I just hired the pro and got a guarantee. Well, today I got the finial off the antenna, next is to rip into it and put that piece of cable you gave me in there. What kind of solder should I use to attach the cable to the antenna ?

Yeah, so I have a decent looking '90 coupe, and recently picked up a second one of the same car, as a parts car. As dictated by Murphy's Law, the headliner on the car I like the better of the two is in bad shape, but the one on the parts car is in mint condition. I've read some old postings by Barney and others about doing the headliner job but seriously doubt I'm competent to do it, I lack patience for that sort of thing. My question is, ..... is a headliner job something that qualified labor is commonly available for ? i.e., where would I look for someone to do it for me ? Obviously, an "auto upholstery shop" in the yellow pages, but before I delve I thought I'd maybe just pick your brains for any tips or pointers, what to look out for, etc. Thanks !! . oh, and BTW, if any of you has some time on their hands... and want a little job.....

Never mind !! I found it. Searched about 15 minutes, then posted the above. Then I found it, duh

One of my bulbs is out on the center, rear dash. I removed two long black phillips head screws from the latch looking thing above the hatch door, and the panel around the center stop light bulbs is looser than it was before, but doesn't seem to want to come out of the way cleanly, ugh. Before I break something , is there a simple way to get to those light bulbs ? Thank you