Hi,
My Lexus GS300 won't shift any further than 3rd gear.

I've got 2 error codes
P2714 - Pressure Control Solenoid ‘D’ Performance or Stuck Off
P0761 - Shift Solenoid ‘C’ Performance or Stuck Off

When I clear codes using Techstream car will go into 4/5/6 gear but after a 5-10 minutes codes come back and it goes into limp mode.

I already changed all Solenoids and oil - no luck
Next step I changed gearbox and oil - no luck
Lastly I replaced ECU - no luck

Do you guys have any suggestions/ideas ? what else could I check in this case ? It really drive me nuts...

 

The solenoids that you used were they oem? If they are oem maybe its a wiring issue, from the harness plug to the bulk head connector. Do you have a good scan tool that can ping test solenoids?

 

I have more symptoms (maybe your transmission has them and you didn't notice):
- after third gear, car revs up like is in neutral. Changing gears manually or reducing speed for the car to automatically select gear 1, solves the issue
- sometimes revs up and down quickly like it's slipping then catching, then slipping again.
- some other times revs stay fixed while vehicle speed increases.
All this happens if accelerator is pressed moderately. If I drive in manual mode and keep the rpm between 2000 and 3000 , all works fine. Also drives fine if driving on auto in such a way that rpm stay above 2000.

I tested the solenoids at the computer connector:
- those which need to have 5-5.6 ohm have around 7 ohm (SL1, SL2, SLU, SLT); except SLU (which makes operating noise on connect) all make operating noise on disconnect.
- those which need to have 11-15 ohm have 15.3 (S1, S2,S3), except S4 which has 13.7 ohm. All make operating sound on connect and disconnect.

While writing, this i hoped this could be just an oxidized ground, but the SLT category solenoids have both + and - coming to the computer.
SLT has 1.4 -2 ohms more, meaning 0.7 - 1 ohm per wire.0.25 mm cable to have 1 ohms need 2.5 meters. 0.5 mm cable need 11.5 meters. So the deviation seems plausible.

Oil has been changed without modification of the symptoms.
Stall test returned normal results(because of brakes could test only in reverse)
Hidraulic pressure measured to be in specs (only reverse and idle tested properly)
Torque converter engages without noticeable lag (hard to stopwatch the engagement time), makes no noises, lockup works over 80km/h

Where i live, automatic gearboxes are alien tech and people just replace the faulty transmission with used ones or replace everything inside without doing diagnostics.
In this order , I'm looking to:
- have a working transmission
- properly diagnosed and fixed
- gain some knowledge myself so I can share the knowledge about the alien technology.

Did I miss something? Is there any fault in my debug? Is there another forum better suited for this question?
Next step would be to check the valve body.Any experience or feedback is welcome.

 

Have you tried sending out the ecu to get it tested? Main issue with GS300 is transmission module inside the ecu

A lot of people send their ecu's to SIA electronics and if I remember correctly cost about $115 to test and repair the ecu

 

ibidu1
Hi
pack of all solenoids was from ebay, I read that it did the trick and worked for other member of the forum. So in total i used 3 different packs of solenoids, 1 original ones, 2 was from ebay( chinese ) and 3rd one was the one that my used 2nd hand gearbox had so I doubt soilenoids are the problem.

Yes I do have techstream

Whats the best way to check the harness ? can you explain in details how would you do it ?

Dentys :

Mine SL1, SL2, SLU, SLT were 5.6 Ohms and S1, S2,S3 were around 13,5 Ohms
how did you test Hidraulic pressure and Torque converter ?
In UK refurbished valve body costs almost the same than used gearbox so I picked used gearbox.
In other thread someone said that gearbox chip is integrated into main ECU so maybe thats the problem in your case, but in mine replacing ECU didn't help.

 

http://nano-net.ro/GS300_2006 here I have the repair manual. You go to your gearbox and you'll find troubleshooting steps and how to do it.
The manual won't say how to test that harness specifically, but since you measured your solenoids and know their value, you can measure them again at the ECU connector and see if any wire has different resistance than the others. It's of interest to me which values you find.

Since I don't have a car lift, I'm looking for shortcuts.
I did a stall test on the torque converter as described in the manual.
There's a port on the gearbox where you can connect a pressure gauge to measure the oil pressure so you can test the oil pump.

Did you change the torque converter too?