928owner

Hi,

I have a problem that just started with the transmission in my SC400 (A341E) which has got me stumped. When cold (first thing in the morning, or left sitting for 5 or more hours), the shift from 1-2 is delayed and harsh (shifts at about 4-5k, depending on accelerator pressure). After a couple of thes "late" shifts, it is fine all day until it "sits" again without a hint of late shifting. This only occurs when it shifts from 1-2 and only the first couple of shifts. The fluid has been changed twice since the problem started and is (and was) clear. The fluid I removed was not bad, and there were no visible metal parts (beyond the normal stuff) in the pan. I bench tested all four solenoids and they all appeared fine. Also, I live in S. CA, so it does not get really cold.

I am beginning to suspect a problem with the ECU, but there is limited troubleshooting in the factory shop manual for isolatating this issue. I have researched every site related to the A341E, but have not found anything which would help (except the old "change the fluid" fixes... that is NOT a problem in this case).

If anyone has had this problem, i would appreciate some pointers. The transmission, besides this, is flawless, and I know if I go to a shop, they will try to sell me an rebuilt tranny, but I just don't believe it has gone bad. It has been serviced every 25-30k miles since new, and besides a front seal, has been trouble free.

If anyone has experienced this problem, I would appreciate their input.

Anyone???
Thanks very much!
928

Jet

928, I have seen similar problems on other models and what end up to be the fix was the shift solenoids, not saying in your case it is but i would definally look into it .
You said you bench tested the solenoids, did you just applied 12v to make it click? or did you ohm the solenoids out when its cold(ie. let it sit for a couple of hours)? did you try to pull codes out of the engine ecu?
these shift solenoids, as far as i know is duty cycle by the engine ecu to control its operation, and obviously the duty cycle rate is what determines the "optimum" shift quality/point. and if you have a solenoid that fails to perform as it should when the ecu is telling it to than that could very well be the problem..... just my 2 cents.....

p.s the trans. code should be A340E.

Jet.

928owner

Jet,

I thought it was A341E.... hmm, I will re-check the shop manual when I get home. You may be right regarding the solenoids.... I applied 12Vdc and they worked fine. The connectors disitigrate when removing, so I had to put them back the best I could, but as I said, when the car warms up, all is fine. I am wondering if the No. 2 speed sensor rotor may have been damaged. This is located on the tailpiece of the trans., close to the govener. I used to hear a slight clicking noise when cold in the trans, area at slow speeds, but it had done that forever. I am wondering if the #2 sensor is not working, and I will pull the codes this W/E. I can monitor the signal from the ECU with a DVM to see if it engages, so that may be where the problem lies.... if you have any other ideas, I welcome them!

Thaks Jet!!!

928

Jet

928, I dont think its the #2 speed sensor, because if it was than the problem will be constant not to mention other system failures.
also the engine ecu look for this signal input for proper trans. operation and to provide vehicle speed readings. so if theres any speed sensor malf. it should trigger and store a code for it and the sensor located on the side of the trans. it's used to detect the input shaft speed i think....
Anyway, try to pull codes and see if you have any and i would bench test the solenoids again, ohm it out when cold and compare it to spec and see.
you might need a oscilliscope of some type to monitor the duty cycle wave form from the engine ecu on those solenoids. try it with an dvom and see if you can get anything out of it.... good luck.

Jet.

928owner

Jet,

Again, thanks for the info. I have the shop manual and the AllData stuff (which is virtually the same as the shop manual) and the information is limited on troubleshooting this condition. Yep, it is a A340E, the reason I was confused is that in the shop manual, the A341E is mentioned in the description section.

Since this seems to be related to a warm-up condition, I am wondering if the ECU is at fault. Perhaps it is processing a "false" condition when cold. The good news is that I have a spare ECU to try. I will do this when I pull the codes this W/E. I will monitor the output to the solenoids during 1-2 shifting to see if it becomes active or is "delayed". Do you know which solenoids controls the shift from 1-2? Once I motitor the signal with a DVM when in actual use, I will be able to see if it is a source problem or the solenoid itself. As I said, I pulled all 4 out and tested them on the bench wit 12vdc. They all activated properly (however, they do not move much), so I am leaning to the source signal as the fault. Since the connectors to the solenoids literly fall apart durng removal, do you generally replace the conectors of just solder the connections in place when you have tested them? The plastic connectors do not hold up well in the fluid after time and are brittle. I dread pulling the pan again, it is laways a mess no matter how careful one is.

Thanks,
928

Jet

928,
Try plugging in the spare ecu and see what happends since you have access to one.From what i could dig up as far as the shift solenoids are concerned, you should have 2 solenoid that is short in length, those controls the 1-2-3-OD i am not sure which one is the one that controls the 1-2 up shift. you also have a long solenoid and a solenois thats in between the two described as far as length wise. the middle length one is solenoid 3 the longest one is solenoid 4.
I dont think you can get those broken connectors at the dealer, i know for sure those later year models you can purchase just the connector instead of the harness it self and do the wire repair that way.
I definally agree with you on pulling the pan, what a pain in the butt it could be, going back up is not that much fun either... let me know what happends after the repair...good luck.

Jet

got_trd

I might have one for sale... PM me if interested

BLK13X

Have you tried resetting the ECU for the engine and the gearbox? Also, what transmission fluid are you running? Should be Toyota Type-IV ATF (well, for the 1UZ's anyway... 1JZ's just use normal Dexron-III).

Taken from http://soarer.ace.net.au/index.html

Try that I go through this procedure every month hehehehe

928owner

Ok, here is the "latest". No codes were stored. I R&R the ECU, exact same issue, so that is not the problem, however, there still there may be a sensor issue which is sending the wrong information during "warm-up". The main throttle sensor and engine temperature sender share a common signal, the sensor ground, E2. Since this appears to be only an issue when starting from a complete cold start, there may be some relationship.

I now have the solenoid signals (1&2) extended on a cable so I can monitor the shift voltages. I also have the No. 1 speed sensor monitored, but I now believe I should have monitored the engine temp. sender/throttle postion sensor. One I start recording the data, I will be able to determine if the solenoid voltages are correct. Keep in mind, I only get a couple of chances as soon as the transmission does this a couple of tmes, all is ok.

FYI, this transmission has seem only T-IV fluid (or the predessor), and has been serviced all it's life.

If anything, it is a "head scratcher", that's for sure.

Very very intersting...

928

928owner

Follow up,
Jet,
Will the LS400 tans bolt in? The reason I ask is there are a few of those available used (in case I need one).

First check shows the volatge changing from 0-13.5 on SOL 2 when cold, but no shift until about 3.5k-4 rpm (depending on load). Again, after the first couple of late shifts, it performs perfectly. I have a feeling the govener or oil pump may be in question, although I will re-confirm the voltages on SOL 2, and check SOL 1 tomm.

Interesting problem. The thing that amazes me is that it just does this when cold... when the car has shifted a couple of times when cold, all is well, even after driving hundreds of miles, stoping for an hour or three, then driving again.... only happens when cold.

928

Jet

928,
Keep an eye on the idle speed tomorrow when you are doing your test. . The trans. unit should bolt up, since is the same engine on the ls400, althought they share a different trans. indentification code, i dont think its much of a difference at all.

the voltage at the solenoid1 and 2 shoud be either on at battery voltage or off at o volts. if the car shifts from gear to gear than the engine ecu is commanding it. if you are getting battery voltage at those two solenoids then i would check solenoid number 4 next. solenoid number 3 and 4 are duty cycled solenoid so you should see a duty cycle at a slower rate when the car is idling, during shifting the duty cycle will increase. since solenoid number 3 is used for lock up, during shifting you won't see much until lock up is needed. if you see the duty cycle increases on number 4 during shifting during the shudder than compare it with the readings you get once the car is warmed up (shifting fine). like how early did the ecu turned this solenoid on during the shudder period and compare it to how early the ecu turn it on after warm up during the 1-2 shift.. this way you can tell if its the sensor to the ecu that caused the out put to be different or is the solenoid not working correctly when commanded to.

temperature plays a very important role in this whole system, if you have a faulty winding inside one of these solenoids its resistance will change past its specification when the temperature starts to increase and it might not operate as they should like not duty cycling properly when needed to and that could very well be the cause this.

Jet.

928owner

Jet,
Thanks again for the info.

This appears to be more common than I thought as a couple of posts are referenced in the SC forum. I am beginning to believe it is SOL 3 or more likely 4. When the problem occurs when cold, SOL 2 voltage is 13.5, but the trans won't shift until the voltage in SOL 1 reaches the third shift trigger point, even th. Once warmed, it will shift in to 2nd when the voltage in SOL 2 reaches the 2nd gear shift trigger point. So this means they are working correctly. Since SOL operates the accumulator pressure point, I am suspecting that this may be the culprit, so I will monitor it. SOL 3 & 4 are "active low" if the wiring diagram is accurate. That means when active, the voltage will go from 13.5 to .6, the drop across the transistor, when monitoring at the ECU control pin.

This is getting interesting, and if is something related to SOL3 or SOL4 may save hundreds of dollars for those who replaced the whole transmission. The reason I believe this is an electrical issue is in the way it occured. Generally, as in my old poweglides and turbohydros, a problem like this would be gradual, as with wear, not immediate (unless I was doing a neautral drop at 5k, but is has been many years since I did such things). The other problem was with the vaccum accumulators which failed exactly like this, I truly believe this is an electircal problem as the accumulator is solenoid controlled.

Intersesting problem to solve.
928

Jet

928,
The ecu shifts the trans. by using a combination of these two solenoids being on or off. so you wont see them stay on or off for a long period of time except when shifting. as long as you see a voltage at the solenoids during the shift pattern than they should be ok.

solenoid number 4 are for accumulator pressure control which dampens shift shock, number 3 is for lock up control.

I can only imagine seeing about 5 volts around solenoid number 3 and 4 since they are duty cycled solenoids. try doing the test on them and compare.

Jet.