Hi all, First time poster, long time lurker.

I'm having serious problems with my Gs300 transmission. It all started 6mths ago the same day I had a new starter fitted by a local guy. When I picked the car up from his shop I started it up (it started on the button again, wahay!) I put the car into drive and there was a clunk from underneath the car as I drove off and it quickly appeared something was amiss, the shift was hard and the car was driving unusually rough.


I brought it back to this "mechanic" the next day and he said he'd have a look at it. He had the car for 2 days before he finally found the the problem. It turned out he had inadvertently pinched a wiring loom situated beside the starter motor. He said he would fix it no problem.The next day he dropped the car to my home and told me it was fixed. I started the car, drove it around the block and the clunk was gone and the car was driving smooth. Happy with that I paid him what I owed him. He reckoned he'd damaged a loom for a solenoid something or other, happy that the car was now driving I didn't care that much.


Over the course of the next few days the transmission started playing up i.e. not shifting properly but no CEL's showed. About 2 weeks after I'd had the starter fitted, I got a check vsc and CEL and codes P0172 & P0174. I cleared the codes and it went away for about another week, then I got a check VSC & codes for P0171 & P0175, again I cleared the codes and the car was good for another week. I rang this "mechanic" to ask why the car was doing this and he told me the only thing he'd damaged was this loom which he repaired and that it must be a new problem. After suggesting doubts about the unexceptional blend of his chromosomes and bidding him a farewell in a rather uncomplimentary tone, going back to him isn't an option.



Over the last 6 mths this transmission problem has been getting worse. Various mechanics have thrown their tuppence in with things like "unfindable" vacuum leaks, Maf sensors and Throttle Body (both of which I've changed) with no luck and a guy who specialises in transmissions insisted it was engine related as there were no codes showing, I even left it in to a Toyota dealership who couldn't find a fault on the ecu but recalibrated the ecm and ecu to try to fix it with no luck, they told me it had an electronic transmission problem (I know, not very specific.)


Tonight I got an CEL & VSC warning, I hooked it up to Techstream and its giving me an P2757 code "Torque Converter Clutch Pressure Control Solenoid Control Circuit Performance or Stuck Off." And the transmission intermittently refusing to shift down even when I tried to floor it.

So I'm beginning to 5$it myself a little.


Is this a new transmission or expensive recon job or could it be just a wiring problem, and if just wiring, where would I start looking for the problem?

Sorry for the long winded post BTW.

 

First and foremost welcome to Club Lexus!

Now on to your problem....sounds like the harness could have shorted out some solenoids or even worse the TCM...

What's the mileage and have you ever had the transmission fluid changed?

Unfortunately with you just clearing the code but not fixing the problem you might have cause even more damage.

I would have made the mechanic that damaged the harness responsible...period...even if you had to go to court because you might be out of 6k if you have to replace the transmission...

 

Thanks for the welcome, Gotcha.

Shorted solenoids.... Does that mean new solenoids or replacing looms? Solenoids sound expensive.

The reason I cleared the codes was that they didn't seem transmission related, I thought maybe a hose was loose somewhere.

The mileage is 140k and I've never changed the trans fluid. The car has been smooth until this incident. There is one other detail that might hold some significance is that when I put the shifter into Park it takes about 30 seconds before it actually clicks properly into park. I'm thinking something in the linkage has affected the torque converter, or maybe the transmission isn't sitting properly on its mount, I dunno, just guessing...

 

I would take it to a lexus dealer and pay for an hours worth of diagnostics. Explain to the tech your situation and see if they can solve it. To me it seems like the first mechanic messed up a few more wires then he fixed.

 

I left the car into the Toyota dealership only last week for diagnostics, they repair and sell Lexus' & Toyota's. The techs are usually very good at diagnostics, the service manager told me the tech took the car for a drive and he said mechanically the transmission is fine, he said my problem is electronic, the car isn't shifting down on certain gears and I would probably need a new loom @ €1600 to correct my problem but at that point I had no CEL's or check VSC, I only got a P2757 DTC yesterday.

I'm gonna leave it back in to Lexus tomorrow for a diagnostic.

Thanks for your help, guys.

 

I hope that it is just the harness...I would get that replaced because either way you will need that to be done even if the transmission is bad.

Also, I would still get the fluid changed as well since you are way over due.

 

The 06's have been known to have damaged solenoids.

 

Is it me...or does it seem like whenever someone states they are having trans issues, it nearly almostalways an 06 300? Please forgive me, but it's a mere observation, and I'm not being critical of anyone who has has made the 300 their vehicle of choice. It just seems that that car has a decent amount of major mechanical issues, which is why I was advised by a neighbor (Lexus enthusiast and an import mechanic), once I started casually looking at the 3gen GS model, to not purchase an 06.

 

Mines an 06 3rd generation..

 

which = to be an 06 =)

 

Yeah, without being too pedantic. If we're gonna be pedantic then all 3rd gens should be referred to from hereon in as 05 - 12 :-)

 

I think it's because the 06 model is the oldest and most likely they have the highest mileage. 300-350 share the same transmission...ive heard of some 06-07 LS460 having the same issue as well...and I think it's related to the long transmission fluid drain intervals...almost everyone I've heard with this problem is over 110k and has never had the fluid changed.

 

What Gotcha said regarding the transmission...

FWIW, my 06 has 94k, and I have done the transfluid drain and fill 4 times. twice one month apart at 50k and recently twice one month apart at 90k = no issues

 

Welcome to CL... Ima make this short:

06 GS300

Your problem sounds pretty similar to mine earlier this year, shift solenoids stuck open or close, similar codes, CEL, etc.. Went to different mechanics and dealerships for months.. Ended up dropping in a new transmission at 120k miles, probably not what you wanted to hear but I think that may be the case for you as well. Few months later, ECU went out. A different dealer said the transmission the previous Lexus dealer had put in for me was not compatible with the current ECU, so I filed a claim with Lexus Corporate and they covered 50% of the cost of a new "updated" ECU.

And yes, previous owner never had tranny fluid changed or flushed. Lexus USA doesn't recommend it for the GS300, but Canada does....?? Same car, same transmission.. odd. I plan on changing it with the new tranny.

Wanted to sell this 300 and get a 460 instead, but I'll be keeping this for at least another 90k after spending $$ on a new tranny and ECU.

Good luck with your's

 

Ok, I've been busy all week and I didn't have time to get this car booked in for a diagnostics. On Thursday I was out driving around in heavy rain and the car seemed to be driving nearly perfect which I find strange, Friday I went out driving again and it intermittently went from rough shifts to smooth shifts, after about 4 hours of driving I had the battery light on and then the car died,a few minutes later.

The alternator is gone by the looks of it. Could a bad or failing alternator cause my transmission symptoms? in the last 12 months I've had 2 starter motors and a new battery. if the alternator isn't the problem what else could cause such weird electrical issues?