Toyota Hilux 2x4 3UZ conversion

[DirkJ]

I have a 3UZ 4.3L 6 speed AT fitted to my Toyota Hilux double cab. for the 1st 2yrs all went well until recently. suddenly one morning when I slowdown there was a hard switch over from 2nd to 1st gear. the only way not to get this was to switch into neutral as I started to slowdown and stop. After which I will put it back into gear. gearing up is nice and smooth its only gearing back from 2nd to 1st that you can feel the hard switch. After replacing the filter in the gearbox checking all the shift solenoids and fill it up with new transmission oil also change the speed sensor. I still have the same problem. Running diagnostics didn't bring up any error codes. We then swop the ECU with another and suddenly the problem was cleared. BUT after about 2 weeks I started to get issues again where it will suddenly on pull away not going higher than 3rd gear and also don't want to gear back. I have to take my foot off the throttle and let it sort it self out. This is random. I also start getting the hard switch from 2nd to 1st as well. but again this is also every now and then not as constant as with the other ECU. Although the solenoids didn't look as if they are faulty how common is it for these solenoids to fail and if they do what are the symptoms?

 

[blinkerfluid]

if a solenoid fails completely it should really register an error code, plus it will shift stupid and not shift in to a few gears.
by your description of the problem its likely you need to inspect the valve body assembly

 

[DirkJ]

if a solenoid fails completely it should really register an error code, plus it will shift stupid and not shift in to a few gears.
by your description of the problem its likely you need to inspect the valve body assembly

thank you for your reply. what I experience is that when I run normal and let the engine/computer do the shifting I have lesser issues. When I run where I can manually shift gears up and down I experience what you just mentioned "stupid shifting" where it will suddenly shift to a lower gear or sudden shifts between 2 or 3 lower gears. In normal auto mode I get with gear shifting sometime not always it will have a hard change over. normally from 2nd to 1st. This is strange. Why when we connected a different ECU the problem was solved but only for a short while and then it started gain. When you mention the "valve body" is this part of the solenoid?

 

[blinkerfluid]

The valve body is the heart of an auto transmission, the solenoids are fitted on this valve body - solenoids are commanded by the ecu to open or close individual hydraulic circuits inside the valve body.

 

[DirkJ]

The valve body is the heart of an auto transmission, the solenoids are fitted on this valve body - solenoids are commanded by the ecu to open or close individual hydraulic circuits inside the valve body.

Do you perhaps have any wiring diagram from the ECU to the gearbox. I can't get it on the Web. Also a board diagram / layout of the ECU. I do have a pin layout of the ECU.

We did inspect the valve body and didn't see anything wrong. Is there something specific to look for on the valve body?

The one thing that doesn't make sense to me is that when we swop the ECU with another ECU the problem went away for a short while. Then came back with different issues on the gearbox.

 

[DirkJ]

The valve body is the heart of an auto transmission, the solenoids are fitted on this valve body - solenoids are commanded by the ecu to open or close individual hydraulic circuits inside the valve body.

out of curiosity I fitted the original ECU back into the pickup. and from the start I had the the exact issues with really hard shift especially from 2nd back to 1st. My next question is If this is from the ECU I assume, I would like to know which connectors on the ECU forms part of the circuit to the gearbox. Is there any board diagram available to see what is going on, on this ECU circuit. I'm trying to understand the how the communication works and what tells the shift solenoids to do what they do.

 

[blinkerfluid]

I may have a pinout and a wiring diagram, pls share your ECU pinout pictures here

 

[blinkerfluid]

Do you perhaps have any wiring diagram from the ECU to the gearbox. I can't get it on the Web. Also a board diagram / layout of the ECU. I do have a pin layout of the ECU.

We did inspect the valve body and didn't see anything wrong. Is there something specific to look for on the valve body?

The one thing that doesn't make sense to me is that when we swop the ECU with another ECU the problem went away for a short while. Then came back with different issues on the gearbox.

You removed the valve body? There is nothing to inspect if you didn't remove and disassemble it.

 

[DirkJ]

Hi. I compiled this from screenshots. They not the greatest quality.

 

[DirkJ]

I may have a pinout and a wiring diagram, pls share your ECU pinout pictures here

I found the following diagrams as well.
Much better quality.

I still would like to know exactly how the communication path works between the ECU, engine and gearbox. Who talks to who and in what order. I know it can be very complicated but would be very informative.

Something else I would like more clarity on is how much a role does a end of life battery and a alternator the over charge plays in possible mull functioning of the gearbox solenoids / whole gearbox. Why I'm asking is because my battery just stop working and then when I replaced the battery we found that the alternator is faulty as well.

 

[blinkerfluid]

erhmm. End of battery / alternator can cause all sorts of problems, I would suggest to fix that area and all power connections. A bad ground can cause such issues as well because then the ECU cannot power the solenoids properly. ECU provides +12v to the shift solenoids and they are grounded inside the gearbox. I don't remember if your gearbox has the SLT or any other PWM solenoid inside the box, in which case both the +/- of that variable solenoid goes directly to the ECU.

What you need is to find the shift chart for your engine / gear variant, they are in the automatic transmission section of the service manual.

The information flow chart is also specified in the manual in a very simple manner - basic inputs and outputs.

 

[DirkJ]

erhmm. End of battery / alternator can cause all sorts of problems, I would suggest to fix that area and all power connections. A bad ground can cause such issues as well because then the ECU cannot power the solenoids properly. ECU provides +12v to the shift solenoids and they are grounded inside the gearbox. I don't remember if your gearbox has the SLT or any other PWM solenoid inside the box, in which case both the +/- of that variable solenoid goes directly to the ECU.

What you need is to find the shift chart for your engine / gear variant, they are in the automatic transmission section of the service manual.

The information flow chart is also specified in the manual in a very simple manner - basic inputs and outputs.

Thank you for this information. Yes I'm busy sorting all the power issues.

Do you perhaps have the service manual for me PLEASE?

 

[DirkJ]

erhmm. End of battery / alternator can cause all sorts of problems, I would suggest to fix that area and all power connections. A bad ground can cause such issues as well because then the ECU cannot power the solenoids properly. ECU provides +12v to the shift solenoids and they are grounded inside the gearbox. I don't remember if your gearbox has the SLT or any other PWM solenoid inside the box, in which case both the +/- of that variable solenoid goes directly to the ECU.

What you need is to find the shift chart for your engine / gear variant, they are in the automatic transmission section of the service manual.

The information flow chart is also specified in the manual in a very simple manner - basic inputs and outputs.

You can email or send it via WeTransfer as well.

You can use the following email address: [email protected]

I will sort out the alternator over the weekend then I can pay attention to see if the random gearbox issues is disappearing

 

[blinkerfluid]

I don't have one at the moment, try here:

https://cardiagn.com/lexus/