I replaced the ‘A’ and ‘B’ shift solenoids yesterday.
No change in my transmission’s problem.
I’m about to give up.

 

That is OBD1 plug. Hate to keep throwing parts at it but without a code present and not able to get a live data stream. Going to be tough. Does the speedometer work? Only other part that controls shifting is the pressure manifold switch.
Brad

 

Is this the pressure manifold switch you mentioned?
There are no contacts in pin location A or B on my OBD port.
i don’t understand why an OBD1 port could be connected to an OBD2 reader.
The speedo works.

 

Yes that is the switch I was referring to. The DLC connector in that year is confusing. Some late 1994 thru 1995 GMs used what was referred to as OBD1.5. Confused yet? The engineers at GM had the great idea of putting the 16 pin DLC but still run the OBD1 ALDA protocol that is completely different than OBD2 protocols. Your vehicle falls into that range of the time GM was changing over to OBD2.

This can’t be read by jumping terminals what is needed is a special cable that works for your DLC and a special scanner. You might be able to find a shop that still has the ability to retrieve codes. OBD1 system was more pointed at monitoring emissions and fuel systems. So may not really point you to what issues you are having as good as the OBD2 would.

Check the fuse for the cigarette lighter also as the DLC gets its power from that circuit. That might be why your scanner won’t communicate. Unfortunately there is no manufacturing standards to follow as each manufacturer did their own thing at that time.
Hope this may help you understand what you are working on.
Brad

 

I keep thinking that the fact that the transmission will start off in first gear and run through all gears except maybe fourth when I first start the car and head out, should be a clue to what the problem is.
After the initial run through the gears, it reverts to starting in third gear.

There is not a tachometer, so I can’t always tell if the transmission is going into fourth gear or not, or if the torque converter is locking up.

it may be my imagination, but it seems the engine temp is running just a touch higher than normal, too.
I’ve reasoned that running in third gear might result in the temp being a little elevated.

i have also determined that the ECM is attached to an under dash panel on the passenger side. I have recently disconnected the ECM while working in that area to replace a door jamb switch that was broken. I thought I’d Take the ECM out and check to see if a pin might’ve been bent in the process of reconnecting it.

I just keep thinking it must be something electrical since it works sorta normally on initial startup.

 

I found a post online where it was said that you can retrieve codes from the OBD1.5 port by jumping pins 4 and 6.
I did that, and got a code of 66. I checked OBD1 codes and it's related to the AC pressure being low.
I couldn't find any codes specifically for OBD1.5.
The cigarette lighter fuse is good.
I've found AC Delco PN 24215111 on Amazon, but can't get verification that it's the right pressure manifold switch for my vehicle.

 

This may help you!

 

OK, now we've got something to work with.

I have ordered a pressure manifold switch and an internal wiring harness. I broke the lock tab on shift solenoid B, and want to fix that. (I strapped the plug to the solenoid with a small plastic tie)
Also, it occurred to me that the problem might be in the wiring harness and I don't want to take the pan off again after the pressure manifold switch and harness are done.

Can you supply a part number for the right 3-2 solenoid? I seem to keep getting a similar solenoid, but the supplier says it does not fit my vehicle.

Any suggestions as to what is causing the code 66?

 

GM# 24227792. The code will set when the solenoid fails. Seems that the resistance is changing after it warm up. They just fail, like a lightbulb over time.

 

ODB1 codes listed here
Code 66 indicates A/C pressure sensor – circuit low pressure.

Here is the Rock Auto catalog already opened to the parts list for the 95. You'll notice that the shift solenoids can be for either port, that said RockAuto shows 3 variations of shift solenoids. Looks like GM may have changed designs mid year. Compare your original solenoid to the ones listed and by clicking on the 'INFO' button provides a Alternate/OEM Part Number.