That torque converter lockup has stopped locking up. Tranny all works well otherwise. Is there anything Inexpensive
l can do to try to fix it? Is there any problem just driving it (seldom goes over 60 MPH @ 3000 RPM). I’m a mechanic by trade, but don’t know anything about this. Shifts up and down thru 3rd gear just fine.
I had the torque converter lockup solenoid go bad on an old Pontiac. It’s possible you have a similar problem but in my case the shop had to drop the transmission. You might be luckier. A good repair manual ought to show the location of the part.
I don’t know the car but if the the converter lock up is electronic look for the easy stuff - there may be a relay, loose or broken wire or connector, etc. A DVM (volt-ohm meter) might tell you a lot. If the ATF is too old something might be stuck - but whether or not to change old fluid will open up a slew of opinions.
Could be a bad speed sensor According to at least one post from someone who had the same problem fairly recently with his. The one i’ve found on Ebay is specifically for the grand voyager.
And the post on a chrysler minivan forum. Cant’ remember if our '88 Grand Voyager had this problem but it wouldn’t suprise me. We sold ours finally in 2014 and it still ran and drove, at least to the end of our private road and back.
TC lockup is most often controlled by the computer based on speed… So the suggestions of checking the speed sensor are valid… With a handheld OBD code reader in “view data” mode will reveal what speed the vehicle thinks its going… You need to know that value… Is the speedo correct?
In 88’ there may also be a switch on the trans shift linkage to tell the computer if you selected D or 3…if that is going out to lunch…then it may just be obeying orders from that switch…so it needs to report proper gear selected…etc.
Next is the tc lockup solenoid…its basically an on/off solenoid that controls the tranny fluid flow path inside the trans and or valve body.
Some are easy to access some are not… look up where your torque convertor lockup solenoid is located and go from there. I wouldn’t go nuts with it…as this little glitch is probably easing you into a newer vee-hickle… You can resist this at all costs…spending more than it would cost to get into something else… or…you can take the gentle hint provided by this issue. lol Your choice of course.
This is a 1988 Voyager . . . definitely not OBD2
In fact, this might be the first year that OBD1 was mandated, for what it’s worth, because as we all know it seems every manufacturer had their own standards
I remember some of the older vehicles had very limited diagnostic capabilities . . . I’m remembering blink codes, analog meters and other things 
It’s been awhile since I’ve had a vehicle this old . . . not sure how hard it would be to find an OBD1 scanner with the proper adapters. And then you’re still limited by the data that the module(s) are capable of displaying
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You could easily read the “blink” codes in that 1998 Plymouth Voyager by turning the ignition switch on & off with a certain sequence.
A code of 15 means a fault in the speed sensor circuit. I recall when that went, then both the torque converter lockup and the cruise control would both stop working. The speed sensor failures seemed common on that vintage Plymouth.
See this allpar link for instructions on the blink codes:
https://www.allpar.com/fix/80s-codes.html
Omg… @db4690 for some reason I had or saw 98’ in my mind…and I just rolled out from there. You could not be more correct Sir 88’ was OBDI i cant argue with that. Which basically negates everything I wrote in my post… LOL…
The guy who drives my ship was out to lunch when I wrote that one it seems. Now that I have taken the wheel again, I’m man enough to admit it. My apologies. It was only a 10 year difference tho right? lol
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