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AW4 Auto hanging onto 1st gear

Check fluid level... if it is not full fill it up, see if it still does it. Also check your throttle valve cable adjustment. If that does not fix it, try putting an extra half liter of dexron/mercon in the transmission. If that fixes it, it may be time to plan for a transmission rebuild soon, every time I have seen one start doing this it was shortly before it quit shifting right. Though it would be wise to put an OBD2 reader with live data on it and see if the TPS and a few other things are reporting correctly as well before assuming the worst.
Oh right, you said 94, my mistake. :looney:
I've been using my 92 to get to work this week while the DD was laid up for a starter replacement, and I'm fighting a very similar issue:

At first cold start, will not shift out of 1st. Once the engine(or is it the trans?) gets a little heat into it, it'll make that shift, and once it manages it once it shifts perfectly fine until the next cold start.

I checked fluid level (good), and readjusted TV cable, no help. Decided that TPS was probably original (or at least 20 years old), and decided to take a $45 punt on a Duralast unit at Autozone.

With the new sensor, time to first successful 1-2 shift decreased a bit, so I was thinking maybe the computer was still "relearning" the new sensor (have not had time to do a battery cable pull to fully reset the ECU), but it's still doing it and I am still concerned.

I will say there have been other improvements: prior to the new sensor, I'd been dropping the shifter from D to 3 for long uphill climbs, as the truck would not maintain speed (and my MPG is a bit off, even for pushing 31-inch MT/Rs on 3:55 diffs). Now, after the new sensor and confirming the TV adjustment is right, I don't have to do that any more. Only filled up once since the sensor swap, may have seen a 1-point improvement but not really enough data on that yet.

Thinking back, I've been having this issue for maybe about a year now (less noticeable/faster recovery on warm/hot days), which may put the start shortly after the last change of ATF (due to a weeping pan seal). Didn't do it myself, and the mechanic used "synthetic" fluid, presumably just a drain/fill since he was just dropping the pan to make sure it was straight to stop the leaking. So, I'm thinking I've got a mix of traditional Dex/Mercon and whatever synthetic fluid the mechanic used, and from reading some older threads around here it sounds like it's not entirely impossible for the synthetic ATF (unknown exactly what type he used, I may try and find the shop invoice to see if he listed the specific stuff) to be a contributing factor. As I have a couple gallons of regular Dex/Merc fluid on hand, I may try doing a drain/refill myself with that after testing the new TPS and checking the two TCM harness connectors by the firewall.

I'll do my best to remember to post any updates.
I'm fairly certain that all ATF is synthetic, actually. It has been years since I even thought about this, so verify that.
Did not get a chance to hunt down the invoice from the shop yet, but still plan to look for that. Know he specifically said "synthetic". Might have been Mobil-1, but until I find the paperwork I can't confirm.

Also, pulled the trigger on a Mopar TPS on eBay this morning - not going to put it in just yet, but I want one on-hand when I do get an opportunity to test the Duralast unit. If that tests out good, I'll just run with it and keep the Mopar one in the console for down the road (speaking of which, I should at some point lay in a spare set of the screws to go with that sensor, as one of them I felt like the new Torx bit I used wasn't engaging very well).
Mine is OBD1. Prety sure my ODB1 Actron scanner only does the engine not the gearbox.

The Innova OBD1/OBD2 scanner I have only does the engine only on OBD1 vehicles.