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Maybe this will help someone. I finally pinpointed the culprit behind an intermittent stalling, rough idle, lack of power situation. It would run perfectly smooth most of the time, until some random moment when it would start acting up (usually when giving someone a ride 😂🤦‍♂️). It didn't set any codes for a while, but did eventually set E042: open spark timing communication circuit between the ICM and ECM. This caused the ignition to spark at a default 10 degree advance at all times, regardless of the situation. Upon inspection of the ICM connector, I found all the female tangs wide open, in such a way that the pins would likely not be making contact, or contacting intermittently. Also, the screw had been tightened so tight that it split the connector in half and made a 1/8" impression in the plastic. After splicing in a new connector, I noticed that it is very hard to tell when to stop turning the bolt. The way it's designed, it has no discernable stopping point because of the rubber gasket inside the ICM. This is a very poor design, in my opinion. I don't know what the solution is, except to count the bolt threads and the number of revolutions of the bolt as you're turning it, to make sure you get a good connection without breaking the connector. There is a section in the service manual on how to remove the tangs from the original connector with a special tool, reform and reinsert them, if anyone is interested. It could very well clear up a driveability issue for you, without replacing any parts. Photos showing how worn out the connector was, at only 21K miles:

I don't have the CRT but even the later model is all displayed in metric units. The FSM only lists metric units as well, so I suspect it is not possible to do in diagnostics

It was also fun to wire because the first time I didn't notice the 2 extra wires and just connected them in order 😂. In addition to them being all white, it also didn't come with the flimsy black plastic cover, which was absolutely destroyed, and I assume unobtainable. I tried to salvage it by melting the broken pieces back together with a soldering iron and fashioning a makeshift hinge out of electrical tape.

Here is the 91 Starter and Charging System. A service manual is a an extremely valuable tool for these cars if you are going to do the work yourseld.

That is what I've heard as well. However, I was unable to insert it without turning the bolt at the same time, because the threaded end of the bolt has a starlock washer that prevents the connector from moving independently of the bolt. I presume this is to avoid losing the bolt after unscrewing it.

Some people remove the internal cushion for the reason as stated. Once the bolt has been cinched down to the point of deformation and then destruction, there isn't a cure for that, except as you have detailed. I am pretty sure the design is for the bolt to be a retainer, not a method to pull the connector together.

I just got that order finalized . 2 grommets and one reservoir cap for $63.00 delivered. The 2 grommets and pigtail I got from Gibson's yesterday were free [Counter guy said "Merry Christmas" I guess it pays to be a frequent shopper]. Seems like a lot of money but they are new and the last set as shown on the Buick Dealer parts network. Like I said parts I may never need but at least I have spares. With the new ones and the 2 used ones that's $15.00 per grommet...

I got back from Gibson's after getting those grommets. There were 5-6 Reattas and a couple of Rivs with the Teves brake system. I only got one set of grommets as I just couldn't see taking apart a Teves unit [and then probably ruining it] just for some rubber grommets. So I went to the local Buick dealer and tried to order these grommets. As you might guess they are discontinued, however there is one GM repair kit left in the country that includes the grommets so I bought it. I'll just add it to my other parts that I may never need, but if I do, I'll be all set.

I was wanting you to do that because if the lights went out when you turned the key it would mean you had a bad connection to the battery. Since your lights don't dim or go out that tells me there is a problem in the circuit that activates the starter. I hesitate to offer to much help on a '91 because there a lot of differences from earlier models and I've never worked on a '91. From what I've read here so far, your problem could be the theft deterrent system locking out the starter, a bad ignition switch or park/neutral safety switch as 2seater said. Below is the path (yellow) the circuit takes if your '91 is like earlier models. Note the starter interrupt relay in the circuit. It is what keeps the starter from turning if the VATS is the reason it won't start. Assuming the '91 is same as other models, I would do my troubleshooting at the transaxle position switch to determine if the starter is the problem or the other things mentioned.

Thanks to a google search, your advice from October 2020 helped me in December 2023. My washer fluid container sprung a leak, and I was struggling to remove it for repairs. Removing the air filter housing revealed the culprit hiding under the Relay Center: a broken plastic nipple on the washer pump. After reading your tip on how to move the Relay Center out of the way, I had the fluid container out in a minute, new $10 pump ordered from Amazon. Owning a Reatta would be a lot more challenging without experts like you sharing their experience. Thanks, greatly appreciated!