Hello, I recently purchased a very clean 05. About a week after owning it, it started shifting very strangely like it couldn’t figure out what gear to be in. It was showing P0761. I eventually replaced the transmission with a used (125k mile) unit. I just got the car back yesterday and on my way home, it started doing the exact same thing. The car refuses to to shift past 3rd gear, in D or manual mode

I am at a complete loss. I find it extremely difficult to believe both transmissions have the same mechanical issue. Especially after scouring this website and other LS groups on Facebook, this problem does not seem to be common. I just don’t know what to do, I am thinking of sending the ECU out to be looked at and hopefully repaired.

Any help would be greatly appreciated - I know it’s not a fluid level issue, the gentleman that installed the “new” transmission had it hooked up to tech streams to make sure the temperature was correct when filling.

 

Go back to the mechanic who diagnosed the first transmission to be broken. They have some explaining to do....

 

Well the original transmission lost reverse, and after driving it to the shop every gear turned into drive. I assume it’s from driving it in fail safe mode. It originally did it on my way to work, so I had to drive to work, back home. Then to the shop, when I received the transmission. The internals were smoked.

 

The ECU is in charge of both the trans control and main engine control as well.
If the shop didn't let it full reset (no battery for 10 minutes) it may still have the old trans memory in it.

 

is there a specific ECU reset? Or should I just leave the battery disconnected for a while?

 

There is a fuse or battery disconnect but most likely the ecu needs to be repaired as there are numerous posts on this ecu problem.

 

its likey the ECU. if the re-set doesn't work, you will likely need to send the ECU out to have it re-soldered or otherwise repaired
lot of good info in this thread
https://www.clublexus.com/forums/ls-...yone-else.html

 

I plan on sending the ECU out today. I really hope this is the fix. I love this car, but have only been able to drive it for a week. I’ve only owned it for about a month. I’ll pull the ECU out and cross my fingers. I really appreciate the insight and help here

 

Yup, the problem is the ECU. No reset will fix it. The ECU needs to be repaired.

Of all the Lexus models, the ECM of the 3rd-Gen Lexus LS430 is the one I mostly receive in my shop.

The issue of not engaging in the 4th gear, other than ECU, is caused by the turbine speed sensor but in your case, I guess that it was included in the replacement transmission, so again, the ECU is the culprit.

If they fix it well, the issue will be solved.

Best wishes.

 

Thanks Rick!
I sent out the ECU today. Hopping to get it back early next week. Keeping my fingers crossed that this will be the end of my tranny problems. I’ve only owned the car for a month, only been able to drive it for maybe a week. Just enough time to fall in love with it.

 

Did that solve your problem?

I sent mine to TechnicalDomain but still having same issue.

 

I sent mine to SIA and it fixed the gear hunting on 3 / 4th / 5th

Plus I had the valve body gone through by my tranny mechanic shop.

Also if your in the Midwest near Milwaukee, I think Lilevo fixes the ECU also:
https://taninjdm.com/for-sale/
H.

 

There is a reset pedal procedure - I never tried it - This was posted some time ago

 

I'm having the same issue. Start your first drive of the day in S mode and see if it shifts properly. Don't manually shift the gears. Just pop it in S and drive normally.