Harsh downshift for 2006 gs300

I am having this same problem with this right now, did u figure out what it was and get fixed properly?

I'm also having the same problem. Lexus dealership told me I needed a ECU update that costs 2k plus an additional 300 for install. I didn't have the money to fix it and now my car is having shifting problems. It got stuck in 3rd gear so I took it in and they said my tranny is starting to fail. Just yesterday my battery light lit up on my dash and today my car wouldn't start. So I jumped it and my power steering is not working at all plus my clock and my navigation/radio is not getting any power at all and all my warning lights on my dash are lit up. Does anyone know what the problem could be??

Yes, I got my ECU replaced and reprogrammed and now my car is running good as new. I don't know why there is not a recall on the ECU because plenty of people are having this problem and are getting misdiagnosed saying it's the transmission. The ECU controls the engine, transmission and anything electrical with these Lexus. I paid about $2,000 and I'm back on the road

I'm not sure how or where to start when it comes to getting Lexus to acknowledge this problem. I didn't purchase my car from the dealer but this is definitely an issue. As far as the actual maintenance once the transmission is change you need to have your computer program so it can learn the new transmission because it's probably still reading the old one.

Ok you guys. I have a solution. There is a place called LKQ that sells used CPU's for a couple hundred. I just purchased mine for $400 and am taking it to the dealership sometimes this week to get it flashed over to my VIN so it can be used with my car. The dealership said they would charge me 1 hour labor to flash and install it in my car, which is $160. My car is jolting when coming to a stop around 8mph. It does it every time and the reason why is because my CPU is bad. In order to order the part you will need to open your hood and ok the drive side, by the windshield there is a black box that contains your CPU. There are numbers on it and you will need to write down the Toyota number. On my 06 gs300 my number is 89666-30352. I called LKQ and they had one in stock. Here is the website https://www.lkqcorp.com/en-us/ The representative at LKQ that Helped me is Missy and this is her direct line 209-235-5142. Lexus also told me I needed a CPU update and a new or rebuilt transmission. My transmission is perfectly fine, I believe. I will give an update once I get my part installed. This is a photo of the CPU I purchased from LKQ

I INSTALLED THE ECU HAD THE FLASH ALL 02 SENSORS PLUGS BELT ND THE CAR DID NOT GO PAST 60MPH ABOUT 3MONTHS LATER VERY DISAPPOINTED WITH THIS 06 GS300 LOOKS GREAT BUT I FEEL LIKE MY 94 GS WAS STRONGER

THE ANSWER IS 89666-30354 ECM COMPUTER & REMAN TRANS NOT REBUILT ND TRANS HAS TO UPDATED TO CORRECT ORGINAL MANUFACTURERD DEFECT SO USED IS A WASTE OF MONEY LEXUS DID US 06 OWNERS WRONG THIS TIME

Wish I would have read Melissa's post first. Gonna cost me $2000 for same problem. Did get a coupon for 15% off. Make sure you are on Lexus mailing list.

I have a friend who has had the same problem with the 06 GS300. Both of us are in the electronics service business so we thought we would have a look at the ECU and see if we could determine the fault. The processor on the ECU was ruled out as the fault, as the unit still shifted, just harsh on the 2 to 1 downshift. We ordered some replacement Electrolytic capacitors and replaced them ( heat can effect these components ). This didn't fix the problem, so some more research and we found a similar problem reported with the Toyota RAV4. This turned our attention to the surface mount resistors on the ECU. After touching up all of the resistors with a soldering iron ( take ESD precautions ) the unit came good. It seems the surface mount resistors are prone to the heating and cooling cycles in the engine bay causing dry joins. If you are, or know someone who is handy with a soldering iron this would be worth a try ( you need to be able to identify surface mount resistors and be able to minimize electro-static discharge or risk doing more damage ). Search for RAV4 ECU repair to see what others have done. Attempt at your own risk and good luck.

I’m having the same issue as you describe. I have a 2006 lexus gs300. I’m reading on the club Lexus forums and a member had sent his ecu to be repaired on eBay. I’m going to try that. I will update everyone when it’s done. I hope it is the ecu/ecm and not the tranny. I had a previous issue with the transmission being stuck in third gear and after recently rebuilding it I’m sure it’s not the tranny.

https://www.clublexus.com/forums/gs-3rd-gen-2006-2011/877281-transmission-hard- downshift-from-2nd-to-1st-gear-feels-like-getting-rear-ended.html#post10090433 hello all, i have found the solution! please follow this link!

FYI, I have the same issue. I did some research and it appears that Lexus knew about this issue and had authorized replacement of the ECM. The Lexus bulletin can be found: https://www.valvebodypros.com/assets/a960_harsh-2-1.pdf The only caveat was that part was only warranted for 96 months or 80,000 and was issued 12/2012. Meaning if you purchased your 2006 car in August of 2005, you would have already driven 88 months with 8 months left to determine this, or if your average annual driving were slightly more than 10,000 then you would have been out of warrantee by the date the bulletin was issued.

My 2006 Lexus GS300 with 146000 miles had hard downshifting from 2nd to 1st. My mechanic replaced the EMC new part number:89661-30W70 old part number: 89666-30350. Fixed problem. He told me that good thing I stopped driving the car as possible real tranmission damage could occur.

well same problem here, dealership recommended new transmission, (they dont fix they replace) lexus shop said needed new ECU. replaced with new for 2200.00, now 2 weeks later started again, stays in first and second gear, RPM spike if you try to drive above 40mph, and for first time check engine, traction lights both came on. i guess next will try shift solenoid

I am having the same exact problem. I took the car to GM Lexus they told me I need a new transmission and a new ECU. The repair would have cost me way above $6000. I took the car to a transmission repair place in Miami. They kept the car for over 3 months, they replaced the transmission with a used one, and replaced and updated ECU. That didn’t fix the problem... I have been my driving the car for over a year just like that, I just put it on neutral when coming to a full stop.... I talk to many GS owner that experienced the same problem. Lexus should recall and repair this problem.... I getting rid of my in February, I will never buy another one....

I had the same issue as described above. I have a 2006 lexus gs300. I’m reading on the club Lexus forums and a member had sent his ecu to be repaired on eBay. I sent to SIA Electronics and got the ECU back and put it in my car and now the harsh downshift is gone! Three different places said I needed a new transmission including the Lexus dealership. I brought up the ECU to them and they said no way. Well they were wrong and almost cost me $4k!

Thanks for all the above information. I had the same issue with my 2006 Lexus GS300, hard 2nd to 1st downshift and my local mechanic said $2400 to repair the transmission. However I decided to try to get the ECU fixed first. So I removed my ECU, ordered the repair on ebay with SIA Electronics in Illinois, sent my ECU to them, they sent it back about a week later (today), installed it back in my car, and my car is downshifting properly. Total cost about $130.00 to repair my original ECU. Did NOT need a new transmission, did NOT need a new ECU, and did NOT need to get my ECU flashed.

So does the 2006 gs300 have a enigine computer and a transmission computer? Wheres the transmission computer located at?....im having same the same problems with my car

search ECU repair cot around less then $150 i found one in IL didn't remember website or his phone but that was i did fix my friend 06 gs300 just send your ECU out he fixing it and send it back will fix your problem or you can buy used ECU matching part # but then the gs300 have that problem with the ECU then you still need to program to able to start the car cuz the ECU won't able to recognize you key fob the ECU located in black box driver side under hood here i found the link https://www.ebay.com/itm/Lexus-GS300-ECM-ECU-PCM-Engine-Computer-Repair- Return-Lexus-ECM-Repair/322526499229? epid=1029794542&hash=item4b1813d19d:g:O4gAAOSw~y9ZJFbe:rk:2:pf:0 hope this help you guy

Sounds like we all have had many of the same experiences. My problem started when bought the car. Apparently whoever owned the car before never got the problem with the hard down shit from 2 to 1 repaired. When we bought the 2006 Lexus GS300 we did not know the transmission was in limp mode and stuck in third gear. We had to first repair the transmission (Rebuilt kit and new Tork converter) but we still had the hard downshift issue. I got to looking online and found I had two options. 1) Purchase an OEM Remanufactured ECU for $869.00 from a company called All Computer Resources. If you have the money and you want to spend it this is a good option and the company seems to be reputable. or option 2) Send it off for repair for $135.00 at Mas Electronics Repair A.K.A. My Airbags. We went with option # 2. They have a 24-hour repair/turnaround time and we figured what is a few more days on top of the already 3 months that we have already been battling this problem. Hope this helps someone like the other comments has helped me.

Had the same harsh downshift problem on my 2006 Lexus GS300 140,000 miles I replaced the ECM and the car is running smooth again. Also did a full transmission flush saved me thousands of dollars it was not the transmission only took it to a transmission shop and had them diagnose my car for $170.

Well guys. I’ve been following the same problems with my 06 GS 300. Is doing the same hardshifting on 2ond to 1. I’ll look on the hood when I took the ECU didn’t have no bolts. Looks like someone already did something to it. I send it to this place that i found on eBay to get it repair. I hope this solve the problem. I’ll let u all know when my ECU comes back to put it back on. And see this solve the problem

Well. I put my ECU back on my GS 300. I drove the car around the house and it was doing fine. I keep driving and it started doing again. Can some please help me o tell me something about it

I'm am having the same problem and that's the reason I'm seeking to see who else having that problem

Has anyone ever sent their ecu to sia electronics and got it back and the car is not starting or firing up

Sent mine there a month ago. Seemed to fix the hard downshifts in my gs430, but now I have a check engine light with traction control lights on. The guy Mike at SIA said to have the computer flashed and or updated. I'm working on that now.

A hard downshift more than likely its the ECM a good transmission shop can detect this when they know what they are doing its not the transmission this was a recall on my 2006 Lexus GS300 only mine was already over the warranty so i ended up paying out of pocket about 1k.

My gs300 runs fine now just took some time for the car to get use to it after being off for 2 weeks they recommend I flash the computer also but I dont see why let me know how that goes @dustin

Hello from Spain. I had the same problem, I read your forum and a friend who repairs ecu fixed it for me. He told me that the problem is because of the solders, they are made with bad tin and it cracks. For that reason the car works badly. I attach an image made with a magnifying glass of a weld, and in it you can see a crack in the weld. To solve it, you will have to take them to a company that repairs ecu and that they replace the bad tin with the good one (I think good tin has lead). They should remove the old solder and put new solder on all the connections and your car will work perfectly again. Thank you all Greetings from Spain

Francisco Javier, can you pinpoint exactly the location on the ecm where the broken soldier at?

He said me , all soldier. You,ll never have problem, said me

Hi I have 2006 Lexus GS 300 . I'm having the same problem with mine however I took it to the shop and they replaced one of the transmission solenoids then he called me back and told me that I had a second one that was out there's a total of 9 solenoids in the transmission well originally when I put the OBD2 code reader on my car it only threw out one code so that's the code that we went to with and then so he replaced one then he said I need to replace two of them so I replaced two with a OEM from Lexus dang those things are expensive they're like almost 300 bucks each so it cost a total of 1450 to fix my Lexus however when I downshift and I come to a stop it's still jerks a little bit it you know a little rough sometimes I was noticed if I stop from a further distance it doesn't do it as bad but I just downshift to neutral or but it only does it when it's in the standard mode if I put it on the other mode manual mode it doesn't do it it's weird but anyways however the mechanic said that my transmissions kind of damaged I guess because at the time when my car first started acting up I drove it like that for a while cuz I didn't have the money to fix it so even though he replaced those two solenoids he's telling me that there's no way to fix that problem now it doesn't make any sense to me it really don't because it did the same thing that it did before only my check engine light's off but then sometimes my and then that but then again my check engine light keeps coming back on it's weird it comes off it goes on and then it goes off by itself and it's telling me to check the VCS.

KATLICIOUS79, you never learnt English grammar?

This post details the solution, which is likely bad solder joints in the ECM. To see which components to touch-up, read details here: https://www.clublexus.com/forums/gs-3rd-gen-2006-2011/1027370-gen-3-lexus-gs300-hard-2-1-downshift-solved.html#post11771920