From what I’ve read, it’s easiest to pull the engine/trans out as a unit, lifting them up and out. Then separate the two for replacement.

Dunno what’s wrong with it, but if you heard a bang out of it when it failed, I doubt it’s something simple and easy like a solenoid replacement.

 

My 2002 factory service manual has nothing except repairs possible on-vehicle (speed sensor, differential oil seal, throttle cable and the like). There's nothing about removing it from the vehicle. I remember seeing at least one YouTube video that says it's easier just to drop the entire front sub-frame and lift the body off the drivetrain, but can't find it right now.

The Factory Service Manual does include a chart of which clutches and brakes are involved with each gear. There's no commonality across R, 1 & 2, unfortunately. Anyway, for what it's worth:

As BMR says, the bang is not a positive symptom.
There is an internal selector valve that's connected to the gearshift selector. The pin in the thing I call "quarter or half circle with bumps" in the picture below has been known to break or come out, which would stop the valve piston from moving in the valve body. (The pin is what makes the valve body move). At least it's reachable without removing the AT.

 

If you start with the shifter in L do you at least get 1st gear? Check movement at the neutral safety switch against shifter and manual valve (with pan drop) movement.

 

Thanks! OleAvalon and JohnGD... to reply in LILO format: 1ST nor 2ND gear selection does anything different.... N/S switch has been Fluked and all normal.... also R&R-ed 2 Connectors on A541E front, to check each 'blade' carefully (all spotless), then sprayed 'em with Electricaal Contact Cleaner just before re-connecting 'em / 'swiping' contacts... several times. >>> That TIP re Manual Selector Valve "clip" is new/useful (Thanks). >>> To re-state again a different way: "am NEVER going to drop Engine/Subframe out bottom of Avy; too many 'antique' Connectors, Lines, Et Al that would likely cause multiple ADditional problems upon re-assembly. >>>>> Have found several useful Tidbits of info on TransRebuilder-related sites/pages/links: several mention that the Wire Harness INSIDE trans for the Solenoids develops "intermittent" breaks, causing DTCs for "a" Solenoid [Main Computer circuits 'test' every Circuit, each Start and each On-Road Cycle ( ~7 mile trip).... and that Harness Issue will drive 'Diagnosers' NUTS. But we ZERO/NADA DTCs. AAAGH! >>>>> Rebuilders of the A541E have discovered ~12 Parts/Issues in these trannys, and developed Fixes and Revised Parts, to make their Rebuilts "better-than-OEM". [*One applies to my situation, perhaps: "Reverse Channel Block Failure".] But spending $2400-to-$5K?? NO.

 

Forgot to ask - what code reader are you using? Also - can you explain what happens when you push the car backward in N? If you've done this with another vehicle, do the front wheels on the broken Avalon skid or chatter -- that is, absolutely refuse to turn?

Also, could you possibly post in sentences and paragraphs? I find your solid strings difficult to break into separate thoughts or statements even with the separating chevrons (>>).

 

You can disconnect the solenoids and with limp mode you should get 1st and 3rd in L and D respectively. That is the manual valve others mentioned.

if that doesn’t work yeah it might be hard part failure.

 

[Paragraph] Ole Avalon: she will not move backward at-all in R or N (locked), which implys a hard-part failure. However (also having all the Shop Manuals and A541E Transaxle internals diagrams), like y'all, we cannot 'see' any specific part that would account for "all" of the Symptoms (especially the sudden occurrence). The MIL is NOT on; have 2 different Code Readers; $90 Bosch, and a 2007 high-end Innova. NO DTCs.
[Paragraph] JohnGD: interesting information you provide; have not heard/seen that any-where before. Will TRY it a.s.a.p. Then, it will be time to R&R the pan. [Only other LimpMode reference i have come across specifically re A541E, is that a squirrely TPS 'can' cause the Computer to go into Limpy...] THANKS, guys!

 

[Paragraph] Ole Avalon: she will not move backward at-all in R or N (locked), which implys a hard-part failure. However (also having all the Shop Manuals and A541E Transaxle internals diagrams), like y'all, we cannot 'see' any specific part that would account for "all" of the Symptoms

Went over Speedkar99's video of an AT teardown on youTube. The only thing I can figure around the lockup during reverse is that the reverse planetary gearset has maybe has a broken axle on one of the 'planets' - it might run ok in one direction, then perhaps jam or tilt when rotated in the opposite, locking the gearset. The rest of the symptoms? No idea. Maybe some torn-up version of limp home mode?

Speedkar's video (I don't think this is an a541e):

 

Yes, he's BACK, after 12 months >> NOT enthralled by the prospect of the ShopManual method/time for A541E change-out... DROVE that sucker with just 3RD and OD - successfully - through the Pan-Demic - then this past February, pulled off the Solenoid Connector (plastic-bagged male and female), and DROVE it "manually". [It had new fluid/filter last year.]
All just hunky-dory... until one day: bang-cluck-bang accelerating "lightly" from a Traffic Light. Avalon "did" then 'find' a gear, and we drove on home with no more incidents.
Next day, changed out the AT fluid, drove 50 miles, and changed it all again. Drove all through March, no issues. THEN, my weekly eBay searches finally found a low-miles Grade A used A541E from a Seller with a High Rating. Bought it for
$375 "shipped" across 4 states.
Cleaning it up today and tommorrow, then she gets all New Seals (including behind the Converter), New WIX Filter, and pan-gasket. Solenoids and wiring harness will be 'ohmed' ("while" wigglin' the wires, too), any funny stuff, and that gets replaced. Park/Nuetral Position Switch will be opened/cleaned/checked with Fluke. TPS getting replaced/aligned too!
Should be "in' by next weekend... and i will be wearing the scars proudly...