Observations/opinions/suggestions would be appreciated.

1995 Park Avenue V6 3800 245K miles. Engine runs great, starts first time every time. Throwing 3 codes: P0755, P1257 and P1670.

Made 10 hours round trip, GA to FL and back. Parked car overnight. Went to store and drove back home, 2 miles. Pulled into driveway and drive belt squealing very loudly. Left engine running, opened hood, and belt beginning to smoke. Stopped engine. Water pump completely frozen-up,

OK, water pump not that big of a deal. Put new pump on, but did not realize that by allowing the power steering pump to hang loosely that I was going to break the oil pressure sensor - which I did break. Not fun replacing the sensor, but did finally accomplish that. Thought everything was ok, once again.

Couple of days later, wife going to drive to town and I watch her pull away. The car/engine seems like it is taking a lot of effort/rpms to start rolling. She does however drive away. I forget all about it, and a couple of days later I take the car for a drive. Cranks fine, backs out of the drive fine. I put in D and mash the gas and mash the gas and slowly the engine increases revs and slowly starts moving forward. Something is definitely not right. This engine has always had a lot of get up and go and now it doesn't, at all.

I take the car to a local garage that can read the PCM and they give me codes P0755, P1257 and P1670.

I have been totally dumbfounded at the lack of information around concerning both the wiring schematics/diagrams for this year make and model and the meaning of the codes. I have arrived at the fact that I may have an electrical problem, a solenoid(*) problem, a transaxle problem or a combination of the three.

I am leaning toward doing the electrical examination of the P1670 aspects first and hopefully that may eliminate some of the other codes if I do find something. https://www.gmforum.com/1992-1999-91...-287825/page5/ goes into some detail on P1670 and it turns out to be the transaxle - I'm obviously hoping for some other outcome.

I am a novice, at best, when it comes to mechanics. Any suggestions as to an orderly approach to my situation would be appreciated.

It'* in limp mode.

I don't know why I posted that incomplete reply. Of all the things I ever lost I miss my mind the most. Don't worry I have enough live brain cells to get you through this.
Does the car shift at all? It may be in 4th gear and not able to shift.
The P0755 is a shift solenoid code. That needs to be fixed before I would want to drive it.
Do you have a scan tool that can read live data on your car?

I don't have a scan tool. I got the codes from a transmission shop that has a OBD I that could scan the PCM for codes. The mechanic there drove the car and told me it was stuck in 3rd gear.

Thanks carfixer007. I changed the trans fluid and filter hoping that maybe some trash could be clogging something - no joy. But, everything I am reading about limp mode, my car doesn't seem to be doing that.
Although the transmission shop mechanic said it was stuck in 3rd gear, once the car gets going, it goes on up to 55mph without any problem with the engine around 2k rpm, and I think would go faster without going much higher in rpms. Again, from what I have read, that doesn't sound like limp mode.

I have been really disappointed with wiring schematics (not) available for this car, but from what I have been able to find, the solenoid B (inside the transaxle) is not the easiest thing to replace - so I thought I'd verify all the wiring is good before going to that extent.

Here'* a wiring diagram. The full diagrams for the PCM. I have the factory info for your vehicle.
You are in limp mode. I wouldn't drive it like that or you'll lose the transaxle.
Do you have a dvom and know how to use it? I can get the info for you. The side pan on the transaxle needs to come off if the solenoid needs to be replaced. It'* not a horrible job but it is a little tough if you've never done something like that before.
Let me know.

I forgot to tell you. Your problem is with shift solenoid 'B' in the last diagram lower right area.

BTW....Let me know if you need help with the voltage and resistance tests for that solenoid. The first thing would be to disconnect the wiring at the transaxle and do a resistance test of the solenoid. It'* common for them to go open.
Let me know what you get.

carfixer007, thanks a million. I do have a dvom and know how to use it. Any information, voltage/resistance, etc., would be appreciated. I will either fix this car or it will go to the junkyard. The engine runs great - the car is a dream overall - but it being as old and with as many miles, I don't really see putting a couple of grand in it for a new trans.

I have not even located the PCM for the Park Avenue, yet. I have found info that it is under the dash on the passenger'* side, and also info that it is buried under the air filter on the driver'* side. Either way, unless it is quite evident from how the PCM connectors are labeled, I don't know what is A1, etc. per the schematic you gave (thanks for doing that.)

I will say that the diagram for the PCM connector pins given by AutoZone are C1 1 - 80 and C2 1 - 80 which seem to correspond to the schematic given by the Haynes which I have.

I would appreciate you telling me how to get to the solenoid B. Does the transaxle have to be dropped or can it be done without dropping it?

I will not be able to do anything tomorrow, but on Friday I think I will be starting the probe. I think I will try to do some electrical checks before getting into the transaxle.

Thanks again.

If you look at the diagram you'll see the connector at the trans has it'* location. Open the hood and on the right side (as you are looking from the front) under the cruise control servo (it has the cable coming out that goes to the throttle) you'll see the rectangular plug that goes into the upper part of the transaxle. Unplug that and probe the 'F' and 'E' terminals of the female. This is the solenoid. Let me know what you get.