Chrysler Repair: 1991 plymouth voyager le transmission, vehicle speed sensor, solenoid pack

Question
Appears to be in limp mode. We have changed the oil and the filter in the transmission. Instrument cluster only works intermittently. When it does work, only the tachometer, fuel gauge, and charge gauge work. Kills the engine if you drive too long. Die quicker when driving at higher speeds. I've found that it could be the vehicle speed sensor or transmission speed sensors or a bad connection like on some of the newer models.

Also found this: on ALL a604 transmissions... there is a splice point... to make these transmission work properly...
that splices together a red wire from the Solenoid Pack, a red wire from the TCM/EATX, and a wire from
where the EATX Relay is plugged in...
The TSB Addendum was sent out to the production line...
Because they where having the Same problem... Right from the Get Go...
they spliced the three wires together, capping off the remaining wire... and electrical taped the
wires together and pushed them into the wire loom...
Have you heard of this and where would I find this? Any help would be greatly appreciated as it is our only vehicle right now. Thank you.

Answer
Hi Mark,
I'm working with the '03 manual which I believe would be reflective of your '91 and assume this is the 3.0 or 3.3L engine. The best way to diagnose the problem is by use of a plug-in code reader such as the Chrysler DRB-II or a SNAP-On brand scanner designed for the OBD-I system of codes and which plugs into the data link connector in front of the left shock tower. You would want to ask it to read the transmission controller fault codes (as opposed to the engine controller fault codes) both of which are 2-digit numbers with overlapping numbers so you have to be sure to get only the transmission fault codes. I would recommend that rather than guessing why you have the limp-mode.
The splice you refer to appears to be located in the front right corner of the engine compartment (near to the TCM box and is located just behind the front panel in a fat harness that runs cross-wise, at a point approximately mid=way between the 2 pairs of relays mounted above the harness and on that panel.
I doubt that splice would explain the problem, however. If you get a transmimssion fault code number let me know what it is as I have the '92 A609 diagnostic manual and can look it up.
Please 'rate' my answer (see below).
Thanks,
Roland