I'm working on this exact issue tomorrow. Check engine light, weird shifting, etc. I did a drain and fill, the light went away, then popped back up a few miles later. I'm going to drain the pan, remove the pan, take out the solenoid, clean it, reinstall with a felpro gasket then do the drain and fill throught the ATF cooler line. My fluid is so dirty that a normal drain plug drain and fill of 2.5 qts. didnt even make a long term difference because there was plenty of contaminated fluid in the torque converter. Rather than do 10 drain and fills, I decided to go the cooler line route.

 

Dont feel to bad guys im going trough the almost the same thing im getting a shift solenoid "a" error and am limited to only I belive 4th and 5th gears and now my car is virtually undriveable slips real bad due to gears not being kicked down correctly. Man this blows

 

ouch!
Yep. that blows.

 

I'd do the drain via the cooler line before cleaning the solenoid - no point in putting a clean solenoid in dirty fluid.

I drained the transmission fluid via the cooler lines today.
Fluid is now bright red and clear.
Makes a nice contrast to the still flashing ect/pwr light

Next stage is to remove the pan, clean the strainer and remove the solenoid for a clean.

I'm going to check the electrical connections first tho, as specified in the service manual.
can these be checked without removing the pan?

 

Seems like it's the solenoid. If you do replace the solenoid, let us know how it goes.

 

Sorry to try to piggy back on this thread but if possible can someone tell me wich is solinoid "A" or post a diagram if they have the service manual I will be doing the the pan drop no later than monday thanks in advance guys ............and the cel my car is spitting out is p0974 incase anyone should have this problem

 

This is one I picked up from somewhere, browsing - it's the a650e transmission as fitted to most auto lexa 1998 onwards

S3 = "C", so I'm gonna guess that S1 = "A"

easiest way to be sure would be to remove each in turn and check the resistance across the pins.
Resistance = 11 - 15 ohms =good

 

Thought I'd mention the following, because the tutorial I followed -
http://bananags.grantham-internation...completetrans/ didn't:

Drain and refill the oil pan first, then do a cooler line drain and refill immediately after.
Otherwise you end up adding ATF to the dirty oil in the sump.
You'll save 2 or 3 qts of fluid, and the job will go much faster.

Also, when you disconnect the rubber hose from the metal pipe in can be a little difficult to remove
"Remember there is no more important safety rule than to wear to wear these - safety glasses"
A face full of ATF is not pleasant, even with the glasses!

 

Yea I saw that cl post where he tested the resistabce and all he did was bend the pins inwards a it started working again

 

That's not quite the point I was making!
The lexus service manual specifies checking the resistance as a way of testing the solenoid.
A high resistance could mean that the solenoid is sticking - and fixable by cleaning
An open circuit (infinite resistance), or short circuit (zero resistance) could mean that the coil in the solenoid is burnt out - which means having it rewound, or replaced.

Obviously, if the solenoid resistance is OK, but you still have the fault - that points towards a fault in the wiring, or connectors.
That MIGHT be fixable by "bending pins", but in reality is probably gonna mean a new wiring harness.

any of the above faults could show as "0974" fault code - the easiest way to tell which part needs repairing is by measuring resistance across the solenoid pins (as a start)