I have been through all the posts on the GS430 (2006) 2nd into first clunk.
Aware that it is probably a ECU/ECM problem.
I have this fault, plus a 3rd back to 2nd minor clunk at times. Otherwise car drives like a new one (200K's)

I have done 3 flushes and driven it 500 Kilometers, (no change in the shift clunk.)
Fluid obviously never changed before. Dark brown on 1st flush, now healthy red, Not burnt.
About to do a drop pan and change filter.
nowhere in the posts on this problem is i it mentioned that if it is a faulty ECU that a scan will show fault codes.
If trans problem, I expect to see a code (solenoid etc)
Should a code-any code -come up for ECU fault?

For clunking have you ruled out the guibo/isolator bushing on the axle? A worn guibo can cause hard shifts, what about motor mounts and transmission mounts when was the last time those were replaced with oem mounts?

Your question, I didnt fully understand! Lets say now your are out driving normal, when the car shifts gears do all the gear clunk? Or is it only 1st, 2nd, and 3rd gear? Maybe if you video record and post it, it might make things more clear to understand

There are certain things that set CEL, but plenty that do not. Not having a fault isn’t indicative of anything either way wrt smaller transmission issues, engine map defaults, etc. But before you attribute it wholly as an ECU/eeprom problem (and I’m aware of the history of that),

- follow what he said above about carefully checking all mounts. On a lot of vehicles, that is a cause of harsh ships.
- take some positive step about servicing the solenoids and seals. A solvent to clean varnish, like SeaFoam or Chemtool B-12 can do wonders. Running an ester oil additive will clean too, as well as, and very importantly, condition seals. This can restore line pressure faults that contribute to harsh shifts.

Any more fluid service at this point won’t likely address the issue as long as the fill volume is correct. The filter doesn’t really clog - it’s got a huge area and nothing to really “catch.” In fact a lot of Aisin transmissions don’t even have replaceable paper filters like that (just mesh screens) or non-serviceable ones.

I’m assuming youv’e seen this thread on the A761e in the LS, talking about ecu repair, but also note the solenoid fixes for some and the key/pedal method of reset:

https://www.clublexus.com/forums/ls-...mission-7.html

3 mounts and driveshaft guibo checked, even checked the diff for movement.
HARD shift from 2nd to 1st,DOWNSHIFT (Hard, but not ultra violent,-not as hard as engaging PARK while car is rolling to a stop.)
3rd to 2nd DOWNSHIFT soft- If it was the only noticeable down shift hesitation, I could live with it.
I will be doing a filter and another fluid top up. (advice by expert here:" get fluid clean drive 500, then do filter and top up."
I'm a sucker for experts on forums, but I will see this one through to the end.).
My original question was;
With this happening, shouldn't there be codes coming up on a scan? Either for Trans or ECU?

Quote
I’m assuming youv’e seen this thread on the A761e in the LS, talking about ecu repair, but also note the solenoid fixes for some and the key/pedal method of reset:

https://www.clublexus.com/forums/ls-...mission-7.html[/QUOTE]
Thanks tradosauru
I had seen that post,
Copied here;
"To reset the ECU without losing your seat and stereo settings, perform the following procedure:

1. Get in your car and insert key. (It doesn't matter if you close the door or not.)

2. Turn the key to the on (not start) position.

3. Press the gas pedal to the floor.

4. Hold the pedal to the floor for five seconds, then turn the key back to the "off" position (don't remove the key), then release the gas pedal.

5. Wait 2 minutes.

6. Remove key.

7. Done

Works on all years, 2002-2009."

I had not tried this "fast" fix. (with a trannie doing ugly shifts, I wasn't concerned about losing seat and stereo settings Not a priority problem to me).

I recall a fast fix on another site I was on some years back that involved running naked through a convent at midnight on winter solstice.
Too cold for that one.

I will take the bait and put it to the test.
Will report back in a few days.
I missed the solstice this year.

problem with the "ECU reset before I even got to my car.
Instructions were obviously for earlier model
1) Get in your car and insert key. (It doesn't matter if you close the door or not).
Problem; No key insert on a GS,
2). Turn the key to the on (not start) position.
Without pushing the brake pedal, this can sort of be achieved.
3. Press the gas pedal to the floor.
4. Hold the pedal to the floor for five seconds, then turn the key back to the "off" position (don't remove the key), then release the gas pedal.
Problem, no key to turn to off, but as I has started this exercise with the car turned off and in drive, I put it back in park and turned it off, and released the gas pedal.
.5. Wait 2 minutes.
This part can be done.

6. Remove key.
I took the key way away from the car.

7. Done
You have been!

Works on all years, 2002-2009.
Nope, Not on a GS.
Waiting for next solstice.

Lexus has a service bulletin for a hard downshift from 2 -> 1 when coming to a stop, applicable to all 2006 and 2007 GS430s, and 2006 GS300 models:

https://static.nhtsa.gov/odi/tsbs/20...61736-2273.pdf

The troubleshooting is fairly basic. No checking of mounts or guibos or other things ... if it has a harsh 2-1 downshift coming to a stop, replace the ECU.

My speculation:
The root cause of this issue is generally failing electrolytic capacitors in the ECU (technically, a PCM, since the ECU and transmission control are integrated into a single unit in the 3GS GS300/350/430.- not sure about the 450h, and the 460 appears to have a separate TCM). Most likely the largest and most prone to failure capacitors are related to driving the transmission solenoids, snd when they start failing they aren't able to send as much current to the solenoids, which leads to partial activation and hard shifting. The 2-1 downshift is likely the most difficult for the transmission, and it is likely the most frequent. Therefore, to my not-at-all-a-mechanic-or-automotive-engineer perspective, the symptom you are experiencing is likely enough to be caused by failing capacitors in the ECU, and the cost of repair is sufficiently low that it would make sense to me that ECU repair would be the next logical repair step.

Thanks, Good explanation.
Sort of explains why there are no diagnostic codes being thrown.