76 views, no replies, seems like everyone is as stumped as me! The more i think about it though, the less inclined i am to changing the torque converter. Doesnt make sense how it is fine after sitting, then driving it fails after 10 ish miles. Shouldnt it fail all the time? Oh well, just remember, Eagles may soar, but weasels dont get sucked into jet engines!!

 

I'm no transmission expert, but your mention of losing reverse reminds me of something I read a while ago. It talks about a relationship between the DSL solenoid (TCC), the B2 control valve, reverse, and a binding hard shift between first and second gear:

http://www.sonnax.com/articles/126-Toyota-U140-U240-Series-Diagnostic-Information

That info is for the U140 (not the U151E) so I don't know if any of that info is applicable, but there might be some food for thought.

And just for solidarity... I dropped my U140 valve body earlier this year and replaced a couple solenoids. After completing that job, I look back and realize that I never should have done that, and I don't think I'll ever do that again.

 

Did you clear codes? What codes came back? If it's still complaining about TCC, then inspect closer for binding, possible crud blocking orifices (especially if the original TCC solenoid tested good).

 

Mahalo Oveur, this link looks great. Looks like im going back into the valve body. I agree, scary job, got worried when the plunger fell out and i didnt see where it came from! Thank god for the internet.

Avconsult, i did do a reset and no codes again until it fails again, then i get the P0741 again. I checked the external harness over hoping to find a chafed or broken wire but no luck.

 

I don't know what kind of code reader you are using, but the better more complete code readers/scanners have the ability to actuate the solenoids manually through the interface. The smaller cheaper devices do not have that capability, but the commercial ones like Snap-On do. If you know what you are doing, you can even actuate the solenoids while the vehicle is in motion. Takes two people and they need to work in unison so as to not damage anything (like downshifting to first at 50 MPH), but if you both know the plan, you can test stuff at motion that you can't test at speed.

If you have bench tested the solenoid(s) and even replaced some of them, then I doubt that's where the problem is. The hydraulic valve that is actuated by the solenoid might be having a problem, but the solenoids themselves are probably OK.

I built myself a little "breakout cable" diagnostic device so that I could hang a couple meters on my solenoid signals and watch them while I drove around. If you could actually see what the TCC solenoid signal looks like under the problem conditions, you might be able to determine if the problem is inside or outside the tranny itself. Might be the ECU issuing incorrect signals to the transmission.

I dug into all of this stuff a little while ago looking for a problem with my U140 only to find out that my problem wasn't the tranny at all. No, I don't want to talk about it, but the point is that I know enough about the transmission only to be dangerous. To myself and those around me.

 

Ahhhh. Good times. Good times:

 

Oveur, pretty sure you're not supposed to see that pile of parts on the OUTSIDE of the transmission. :grin:

So, I happened to locate a fairly complete 2005 HL service manual, with some info in the U141E/151E. My '08 also uses U151e, for which I have detailed system description.

For P0741, the ECU sets the code when:

"Lock-up does not occur when expected above 53 mph, or when lockup remains engaged when commanded to be off."

The ECU compares the torque converter turbine speed to the gear counter shaft speed to control the rate of and status of lock-up. Although the ECU knows when the TCC solenoid is electrically shorted or open, it can not diagnose malfunctions much further.

The TCC is commanded off at zero throttle (coasting conditions).

It acknowledges that the code can result of solenoid, orifice/passage clogging or some other hydraulic failure as the TCC solenoid activates the passive Lockup Relay and B2 control valves in the valve body.

Looking at the system descriptions, it *looks" like a malfunction with the non-electric "Solenoid Relay Valve" would seriously mess with lock/unlock and general shifting. Unsure where that is located in the valve body.

It's also possible your TCC has partially disintegrated, sending debris through the system.

I've never ventured far into an automatic tranny. I'd try fluid changes and flushing, but beyond that, just taken them in a trans shop. Thus far, I've never had a Toy trans fail. Had two Honda's pollute theirs before 150k miles.

Keep posting--curious to read how far you take this.

 

Oveur, pretty sure you're not supposed to see that pile of parts on the OUTSIDE of the transmission.

Haha! No kidding! I was clearly out of my element and that was one of the very few times when I pulled something apart and instantly regretted the fact that I had done it.

The official sound effect is "Sproing!!"

After that ordeal, I was thinking about what could have made my life easier and I bet I could come up with a simple fixture to hold the springy bits in place until I could get a bolt or two in place. I was under duress at the time and couldn't even think about it then, but now that the pressure is off, I've got some ideas.

That said... I'm in no hurry to test that belief and hopefully I never feel the need to do so!

 

Haha, Oveur, i litterly laughed when i saw that picture!! Too soon man.......too soon! "Sproing" explains it perfectly! Im trying to get my hands on a better reader as all i have is a pocket scanner. I did notice that the outer harness was not in its standoff and actually resting directly on the trans, im hoping it was heating up and causing a short. The wrapping did look a bit heated, but the wires inside looked in tact. Will post updates once i have em. Thanks for all the help, my two worst topics, transmissions and electrical! Im actually an airline mechanic and will take that any day!!!

 

The little pocket scanners won't be able to get to many of the transmission parameters. You'll need something a lot more expensive than that.

Before you go dropping that valve body again, the first order of business would be to try to determine if the transmission is doing what it's being told to do, or if it's disobeying orders. Because the solenoids are controlled by the ECU, you can't even be sure that the problem is in the ECU or in the tranny itself. A better scanner could be helpful there. You could realtime what the ECU is telling the solenoids to do and see if it matches what it's supposed to be doing.

Speaking of dropping the valve body... I think some of the solenoids can be removed without dropping the whole thing. Two of the solenoids are shorter than the others and can be pulled without taking the whole thing down. The two shorter ones are DSL and the S4 solenoid. You might have to loosen up the valve body bolts to angle it to one side, but I'm pretty sure you can get at least those two out without taking the whole thing down. In other words, you can get the DSL and S4 in and out without "Sproing".

I'll see if I take a pic of the diagnostic cable I built and in the meantime, here's some additional pics I've used to remind myself of the good times. Remember these are from the U140, so I don't know if they're the same as yours:

 

Sorry... Forgot something... Simply "clearing the error codes" might not be deep enough. This is a learning ECU/Tranny system and it might help to reset the learned parameters. There's other places this is mentioned, but from the link I posted earlier:

Before you order a new ECM, be aware of the following. Keep in mind that adaptive strategy is used to control this transmission and the learned adapts must be reset to avoid damage to the transmission after a transmission overhaul or valve body replacement. Remember that the reset procedure will reset all of the ECM learned adapts, not just the transmission adapts. The Toyota factory scanner is capable of resetting the ECM adapts. Resetting the adapts should be followed by performing a re-learn procedure. Bring the transaxle to operating temperature. Next, drive the vehicle at light steady throttle through all of the shifts and repeat until the shifts feel normal. You may find that resetting the shift adapts will correct any binding on the shift, without having to replace the ECM. I would highly recommend performing the ECM reset first, before replacing the ECM.

Note that I didn't do this on my transmission and YMMV, but there are some sources that suggest this as a first step.

 

Thanks, i ordered a new scanner today, should get it tomorrow. Lotsa dollars on it so i hope it makes a dif!

 

So i got my brand new Innova 3130 digital scanner with fix assist and no codes pulled. I figured since i erased them with my pocket scanner that may be why. Was gonna go drive around to make the code come back but dang it, reverse didnt come back this time so its stuck in my backyard! Gonna have to get help to push it out. Going back to the link you sent, im thinking the DSL solenoid is my problem for sure! Now to figure out which of the solenoids that is!?!?

 

I don't know if the Innova can get to the learned parameters to clear them or not. I do know that the new Snap-On can, and of course, the factory device that the Toyota dealers use can as well (duh). Here's an article that talks about the virtues of resetting the stored parameters and in that article they also talk about the fact that not all scanners are even capable:

This transmission uses linear EPC and shift solenoids. This means the shift solenoids can be modulated just like the EPC. The ECM learns and adjusts the apply characteristics, similar to a 604 or 4T65-E. Like a 604, the old values must be cleared when the transmission is rebuilt. Disconnecting the battery for 5 minutes can reset most models up to 1999. Many later models can only be reset with a scanner. So far, the Toyota scanner appears to be the only one capable of performing this operation.

Full article: http://www.sonnax.com/articles/168-When-in-Doubt-Reset

Here's some more "light" reading on the U151. After studying this stuff, you ought to know which one is the DSL:

http://www.sonnax.com/articles/125-U151-U250-Solenoid-Info
http://natpronet.com/trans/U150.pdf
http://highlanderclub.ru/files/manual/23/203vxt2c/x040001.pdf
http://s3.amazonaws.com/sonnax-dev/uploads/unit/valve_body_layout/269/VBL-Toyota-U151EF-U250E.pdf
http://www.sonnax.com/units/269-U151E

On my U140, the DSL was one of the short solenoids (pictured earlier in the thread). That means it was one of the two that could be removed without dropping the whole valve body. I haven't dug into it extensively, but I think your U151 uses the same DSL solenoid as my tranny and if that's the case, you might be able to get yours out "easy" as well.

One thing you might want to try first though would be to Ohm out the solenoid through the connector on the transmission. When it's messed up, and when it's not. One wire through the connector, and the return connection through the transmission case and engine block.

 

FROM YOUR FIRST POST...I bought the torque converter solenoid and replaced it..

Didn't you just replace the DSL solenoid?

 

Oveur and AVconsult, thank you for all the help. I replaced the DSL solenoid today and drove for about 40 miles, vigorously shifting up and down, all good to go now!

 

I replaced the torque converter clutch solenoid originally.

 

Well that's great news. You didn't have to drop the whole valve body again, did you?

And as for which solenoid you replaced prior to the DSL. I'm also a little confused as to what you did first. Reason is... The DSL IS the torque convertor clutch lockup.

Maybe you replaced the SLT solenoid the first time? The SLT is the line pressure control solenoid and it's one of the longer ones that definitely requires dropping the valve body to get out.

SR is the one you have that I don't (presumably because your U151E is a five speed and myU140 is a four).