Fresh23

I believe I’m having a similar problem to you guys. I have a 2002 Lexus Ls430 and when the car is cold started I have to rev the rpm’s too around 2500 before it catches gear forward and back but after I do this the car is fine no hard shifting or anything but as soon as I cold start it or let it sit over night the same thing and I got a check engine light and the code was P0500. My question is where are the speed sensors located and is it something I can change? Has anybody changed them before?

vinwalt

My LS430 2006 had the same issue. All of a sudden, downshifting from 3-2 gave a sudden jerk and then downshifting from 2-1 was worse. It felt absolutely terrible. I was horrified. I took it to my local Lexus dealer in Dallas, Texas. They diagnosed it as the ECU and replaced it under a recall completely free. I was so thankful. I recommend for anyone experiencing this issue to seek out your local Lexus dealer. They were extremely helpful even though I was driving an 2006 model. This happened on 1/14/2022. The car is 16 years old!

ls430w140

Thank you for sharing your experience. Would you be so kind to post the invoice information from the dealer in regards to recall for 2006 model ECM issues?

Yamae

I don't think that your problem is the ECU's soldering crack issue which is discussed here.

The code P0500 indicates that the speed sensor #2 or it's cable is not OK. It is located near the output shaft of the AT as is shown below. It's all up to your skill to deal with it. It's not easy for me but I think I can handle it. But before I try it, I'll simply check the ATF level since your revving up issue when cold is often related to the simple low ATF level and the pump can't get enough ATF and line pressure is low to engage the gear. Why don't you check the ATF level first?

amusing

Data point 2004 LS430 with 205k : abrupt downshifts observed recently when slowing through 25 mph then moreover at about 40 mph and slowing abrupt downshifts.
Reading this thread and went to internet research I found a West Coast electrical repair service vendor: Digital Auto Technology
https://stores.digitalautotech.com/
1525 Unit C Marlborough Ave in Riverside, CA. I called them and decided it was worth a try. They do electrical circuit repairs for many makes / models see website.
Just 4 day turnaround: it was on my door step. Three minute reinstall and 100 mile test drive confirming it’s fixed. 1 year warranty.
The decal / label on the unit shows “engine ecu” but it is the transmission computer. You bubble wrap it and box it with a copy of you pre- payment copy add a description of symptoms. They disclaimer if vehicle has been flooded or if the computer has been dropped / physically damaged beyond repair.

RKeasler

Just got my ECU back today from SIA works exactly as it should, pissed that Lexus was going to charge me 2800.00 for a new one, ask the Lexus service guy if Lexus had a fix or replacement for this known issue he said he wasn't sure but never checked I'm sure. I will write them the review they ask for expressing my displeasure at them not standing behind this issue, whatever SIA did Lexus can do but won't apparently

1Stix

Vinwalt, Thanks for sharing. I'm not sure how Lexus dealerships differ. I am debating on taking your approach vs. pulling the ECM first. Do you know what the specific recall was?

NettyNeuro

Hi vinwalt, I am experiencing the same issue on my 2005 LS 430 and am in Dallas too. Which dealer did u go to so I can try the same route? Ty! U can email me at nettyneuron@gmail.com. Ty!

V8_Fan

My 2005 LS430 started downshifting roughly at 20mph, 12mph, and when the tranny is in N and (with brake on) you shift into D, there's a delayed clunk after you think it shifted into gear. Dealer had no clue, suggested replacing the transmission with a junk yard tranny. Took it to a reputable transmission shop which test drove it. They said it's likely the ECU, not solenoids since it happens only on the downshifts, not up and down. They suggested a junkyard ECU. I pulled the ECU and mailed it to RelentlessMotorsports near Dallas. They think it's the ECU. Fingers crossed. Car has been garaged its entire life up until April 2023 (when I got the RCF). Issue occurred after multiple days of 100F temps (and warm, humid nights) followed by a cold (low 60s), dry morning.

LS430Lexus

I had Relentless repair the ECU from my '06 LS430. It was a very good experience. Completely fixed the problem with a quick turnaround. You may also want a drain and fill on the transmission fluid, I did. Good luck.

V8_Fan

i change the WS tranny fluid every 45k miles (and with my 03 LX, the T-IV every 30k mi), so it’s never old.

V8_Fan

Just installed my ECU fixed by Relentless Motorsports in TX. From what they described, the ECU uses a crude form of AI, so when it starts shifting poorly, it learns that behavior and thinks it's doing the right thing. After that, there is no remedy. They replaced what sounded like an EPROM and reflashed it with their proprietary S/W. Installation was simple. On the first attempt, the engine didn't turn over (I have the smart key but inserted it to be sure), just went to 'on.' I then tried starting it a second time and it started right up. The nav displayed a powering up message w/ status bar, so you have to let it power all systems up for a couple of minutes. I let the engine idle for 5 min before driving. Drives like a dream. So far, I put about 25 miles on it (several trips, mix city/hwy driving). I might suggest that the board moderator archive this thread in the known problems/sticky section.