No O/D on A340 gearbox

[seamonsta]

Recently had a problem with my JZX90 1j with said auto in MX83 that would not change up into O/D. Started doing it occasionally then finally wouldn"t change into O/D at all.
So no O/D light or ECT light on dash were flashing which would indicate a solenoid or speed sensor problem and turns out it was the temp sender that goes directly to the ECU that controls the O/D shifting that was shot.
So if you have the same problem and no flashing dash lights then the temp sender ($72 from Toyota) should be the fix. It is located just below the top water neck on the motor.
Tried searching here and a few people had posted the problem before but no follow up answer so here it is...FYI.

[dumbass]

even the early non electronic Toyota boxes had a temp sensor on the box that would not allow overdrive till a certain temp
the later ones with engine ecu controlling auto it just reads engine temp
surprised u didn't have any other issues with engine to make u look at water temp
unless it was a 2nd water temp just for auto
I havnt touched a 1j on ages

[seamonsta]

Nothing to do with engine temp, there are 2 temp senders, 1 in radiator for temp guage etc and 1 specifically for the O/D function that goes directly to ECU from under the water neck.
The sender itself was actually cracked, engine temps were all good. Posted this up as everyone assumes it is solenoids or speed sensor/wiring issue but the ECU will flash the O/D or ECTS light usually if this is the case.

[maj]

99% of the time it is a temp sensor issue, and yes there usually is an additional sensor just for OD function, on my adub it's on the rear coolant housing on the back of the engine.

It won't be a solenoid issue because for OD both solenoids are off. The third solenoid is purely for converter lockup. If you are having solenoid issues, you'll have crappy shifts on other gears as well.
Solenoid pattern
First - #1 on, #2 off
Second - #1 on, #2 on
Third - #1 off, #2 on
OD - #1 off, #2 off

Check the OD pin on the ECT/ECU is getting 12v when you have the OD switch on, I expect it should since the light is coming on, but you never know.
As long as the temp is warm enough and cruise control speed is above minimum, you should be getting overdrive.
Sometimes it can take a downshift to 2nd before an upshift back to 3rd before it'll kick into OD.

[seamonsta]

Well got bit too excited that i had fixed the problem after 1 drive it was behaving and changing into O/D but went back to no O/D the very next morning.
Soooo turns out the ecu had 2 leaking capacitors as well as the dodgey sender, both replaced now and all good for a total outlay of ..... 66c at Jaycar + loss of hair as i have pulled most of it out, what a saga.
I also found out you need a soldering iron that heats to 500 deg c to desolder the capacitors as Toyota use lead free solder from late 80"s (more hair gone), fyi.

[TheStitt]

What a shit fight, least you got it sorted...

[cresslux]

the 2nd temp sesnor is not just for the auto, it also plays a huge role in engine managment. you will notice it will use heaps less fuel now, and probably have more power too.