Thoughts on LS430 rough shifting and A761e transmission
04-05-19, 10:42 PM
#77
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Thread Starter
Update.
Day 22.
Transmission shifts smoothly, way too smoothly. I still can’t believe that all these years I would have driven the car to notice different gears so evidently, but now I feel like I am driving the new car.
Additional observation detail: Average mileage has been improved, 80mph speed fixed at 2100 rpm shows 29 mpg. I am happy. Before it was 21.
Day 22.
Transmission shifts smoothly, way too smoothly. I still can’t believe that all these years I would have driven the car to notice different gears so evidently, but now I feel like I am driving the new car.
Additional observation detail: Average mileage has been improved, 80mph speed fixed at 2100 rpm shows 29 mpg. I am happy. Before it was 21.
04-23-19, 08:24 PM
#78
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Thread Starter
Update.
Day 40.
A761e shows no signs of improper work or faulty shifting solenoid work. However, I may observe a tiny noticeable moment of shifting from 1 to 2nd gear if one condition is met: accelerating fast and roughly for at least 10 minutes (increasing rpm to above 3000). Seems to be that due to increased fluid pressure inside A761e it may actually produce this tiny push, which is barely felt by anyone in the car. Still nothing to compare to rough shifting which was occurring on every day basis before the ECM repair.
Does anyone know if Lexus have actually published the TSB for A761e software reprogramming/flashing for LS430 2005-2006? I was looking for one but couldn’t find.
Day 40.
A761e shows no signs of improper work or faulty shifting solenoid work. However, I may observe a tiny noticeable moment of shifting from 1 to 2nd gear if one condition is met: accelerating fast and roughly for at least 10 minutes (increasing rpm to above 3000). Seems to be that due to increased fluid pressure inside A761e it may actually produce this tiny push, which is barely felt by anyone in the car. Still nothing to compare to rough shifting which was occurring on every day basis before the ECM repair.
Does anyone know if Lexus have actually published the TSB for A761e software reprogramming/flashing for LS430 2005-2006? I was looking for one but couldn’t find.
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06GS300Lex (02-07-21)
05-18-19, 12:31 PM
#79
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Thread Starter
here's the post from another board on the trans reset process. It seems to have worked for me.
https://www.clublexus.com/forums/sc4...t-the-ecu.html
https://www.clublexus.com/forums/sc4...t-the-ecu.html
Three days before, I proceeded with aforementioned procedure. I haven’t noticed much of a change of transmission behavior.
However, at this moment I am at Lexus dealer doing wheel alignment and I asked the technician to go ahead and plug in their Techstream and their authentic cable to do hard reset of ECT transmission memory, which takes around 1 minute.
I will post results later if I notice ANY change (even slight) of gear shifting pattern / harshness.
The problem is due to SIA work on my computer I can hardly notice transmission working anyways, but my goal is to objectively figure out if dealer reset contributes to overall Lexus “smoothness” or it is just waste of time / money.
05-19-19, 03:14 PM
#81
Lexus Champion
05-19-19, 03:34 PM
#82
Lexus Champion
07-05-19, 04:07 PM
#83
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Thread Starter
07-05-19, 04:16 PM
#84
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Thread Starter
Update.
I was able to connect my Lexus to the new Techstream adapter and, finally, I could HARD reset my Transmission memory through ECT reset function. This completely erased long term Adaptive transmission memory, therefore, I could relearn and readapt my transmission to my newly repaired ECM, exhaust system, new injectors, fuel dampers, previous transmission oil changes, etc.
I have to admit that now I understand what does this hard reset stand for. It felt at first like the car forgot all shifting points during initial mild acceleration road test. In contrast to unplugging negative battery cable, this Techstream procedure DEFINITELY erased EEPROM values in my ECM though I have no way to capture this.
I noticed that my shifting is no longer quick as was after repairing ECM. The car nicely and comfortably shifts to the next gear at the right (!) time slower, but very smoothly. I like the changes a lot. I ve been cruising around and road testing the new setup, and I gotta say this hard reset made the big difference.
I can officially say I restored my transmission to factory defaults and no longer have any issues with it (though ecm repair was the major solution), . Problem solved.
I was able to connect my Lexus to the new Techstream adapter and, finally, I could HARD reset my Transmission memory through ECT reset function. This completely erased long term Adaptive transmission memory, therefore, I could relearn and readapt my transmission to my newly repaired ECM, exhaust system, new injectors, fuel dampers, previous transmission oil changes, etc.
I have to admit that now I understand what does this hard reset stand for. It felt at first like the car forgot all shifting points during initial mild acceleration road test. In contrast to unplugging negative battery cable, this Techstream procedure DEFINITELY erased EEPROM values in my ECM though I have no way to capture this.
I noticed that my shifting is no longer quick as was after repairing ECM. The car nicely and comfortably shifts to the next gear at the right (!) time slower, but very smoothly. I like the changes a lot. I ve been cruising around and road testing the new setup, and I gotta say this hard reset made the big difference.
I can officially say I restored my transmission to factory defaults and no longer have any issues with it (though ecm repair was the major solution), . Problem solved.
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bradland (07-05-19)
07-13-19, 08:41 AM
#85
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Thread Starter
There are different ways how Lexus ECM may learn (=initialize) the new behavior after the maintenance was done on various engine / transmission components. The adaptive component in the ECM memory is required for modern cars to ensure the natural wear/replacement/improvement in the engine and transmission is considered by the "car brain".
Anytime the transmission memory is reset with the proper scanner, the road test is required. The following information can be used to allow ECM to learn new values and adapt the transmission:
===
NOTICE:
Perform the following procedures while strictly observing all traffic laws and speed limits.
1) Warm up the engine.
2) From a standstill, achieve highest possible speed with the accelerator pedal opened 15% or less. Keep the accelerator pedal angle steady while driving the vehicle.
3) Repeat the previous step until shift shock no longer occurs.
4) From a standstill, achieve highest possible speed with the accelerator pedal opened 25% or more. Keep the accelerator pedal angle steady while driving the vehicle.
5) Repeat the previous step until shift shock no longer occurs.
===
What i would add is to turn off the engine after the step 3, and turn it back on.
Anytime the transmission memory is reset with the proper scanner, the road test is required. The following information can be used to allow ECM to learn new values and adapt the transmission:
===
NOTICE:
Perform the following procedures while strictly observing all traffic laws and speed limits.
1) Warm up the engine.
2) From a standstill, achieve highest possible speed with the accelerator pedal opened 15% or less. Keep the accelerator pedal angle steady while driving the vehicle.
3) Repeat the previous step until shift shock no longer occurs.
4) From a standstill, achieve highest possible speed with the accelerator pedal opened 25% or more. Keep the accelerator pedal angle steady while driving the vehicle.
5) Repeat the previous step until shift shock no longer occurs.
===
What i would add is to turn off the engine after the step 3, and turn it back on.
09-28-20, 05:19 PM
#86
Driver School Candidate
09-29-20, 06:42 PM
#87
Advanced
Thread Starter
Question to experts in electronics: Is there any slight chance BAD GROUNDING from the transmission or engine could have caused ECM issues which magically disappear once SIA does its fix?
The background to the question is simple - I fixed rough shifting after SIA took care of the ecm, and then I observed faster and more precise shifting after fixing ground cable. i will be testing one more week and if it remains the same, I will likely recommend to everyone who has transmission issues or some sort of engine electronics issues to look at proper ground first.
The background to the question is simple - I fixed rough shifting after SIA took care of the ecm, and then I observed faster and more precise shifting after fixing ground cable. i will be testing one more week and if it remains the same, I will likely recommend to everyone who has transmission issues or some sort of engine electronics issues to look at proper ground first.
10-08-20, 05:41 AM
#88
What a thread! Thank you to all who have participated. My son's LS430 exhibits the stiff 3 to 2 and hard 2 to 1 downshift symptoms. It also has a 4 to 5 upshift bump. Dealer found P0756 code (S2 solenoid stuck closed) - but the car shifts up and down through every gear.
This might be the ground wire you are talking about? https://www.clublexus.com/forums/ls-...ound-wire.html
Do you know where the solenoids are grounded? Back to the ECM or to the transmission case?
Did you check ohms on the solenoids from at the ECM pins?
My plan is to ohm out the solenoid pins and replace any solenoid(s) found defective. If none are found defective, send the ECM to SIA for repair.
This might be the ground wire you are talking about? https://www.clublexus.com/forums/ls-...ound-wire.html
Do you know where the solenoids are grounded? Back to the ECM or to the transmission case?
Did you check ohms on the solenoids from at the ECM pins?
My plan is to ohm out the solenoid pins and replace any solenoid(s) found defective. If none are found defective, send the ECM to SIA for repair.
10-09-20, 04:05 PM
#89
Driver School Candidate
I am in the same boat.
I wanted to try the SIA route first (since it's the cheapest) ... I should have the ECU back from them next week. Will post once I have it back in the car.
https://www.clublexus.com/forums/ls-...rd-help-3.html
I wanted to try the SIA route first (since it's the cheapest) ... I should have the ECU back from them next week. Will post once I have it back in the car.
https://www.clublexus.com/forums/ls-...rd-help-3.html
What a thread! Thank you to all who have participated. My son's LS430 exhibits the stiff 3 to 2 and hard 2 to 1 downshift symptoms. It also has a 4 to 5 upshift bump. Dealer found P0756 code (S2 solenoid stuck closed) - but the car shifts up and down through every gear.
This might be the ground wire you are talking about? https://www.clublexus.com/forums/ls-...ound-wire.html
Do you know where the solenoids are grounded? Back to the ECM or to the transmission case?
Did you check ohms on the solenoids from at the ECM pins?
My plan is to ohm out the solenoid pins and replace any solenoid(s) found defective. If none are found defective, send the ECM to SIA for repair.
This might be the ground wire you are talking about? https://www.clublexus.com/forums/ls-...ound-wire.html
Do you know where the solenoids are grounded? Back to the ECM or to the transmission case?
Did you check ohms on the solenoids from at the ECM pins?
My plan is to ohm out the solenoid pins and replace any solenoid(s) found defective. If none are found defective, send the ECM to SIA for repair.
10-10-20, 05:27 AM
#90
So I unplugged the ECM connector. With valve body and pin out drawings I ohmed each solenoid from the ECM connector back to the transmission. The transmission was at operating temperature and I expected the resistances to be greater than the ranges listed. There was one stand out.
Sol / Range / Actual
S1 / 11-15 / 16.8
S2 / 11-15 / 16.8
S3 / 11-15 / 16.8
S4 / 11-15 / 15.5
SR / 11-15 / 17.1
SL1 / 5-5.6 / 8.4
SL2 / 5-5.6 / 7.2
SLT / 5-5.6 / 11.8 Line Pressure Control
SLU / 5-5.6 / 7.3
Could this be the culprit? In addition the ECM?
Sol / Range / Actual
S1 / 11-15 / 16.8
S2 / 11-15 / 16.8
S3 / 11-15 / 16.8
S4 / 11-15 / 15.5
SR / 11-15 / 17.1
SL1 / 5-5.6 / 8.4
SL2 / 5-5.6 / 7.2
SLT / 5-5.6 / 11.8 Line Pressure Control
SLU / 5-5.6 / 7.3
Could this be the culprit? In addition the ECM?
Last edited by mdpresco; 10-11-20 at 05:07 AM.