195,000 miles
All of a sudden, when coming to a stop, the transmission will down shift to 2nd (I think) then immediately go to first, before stopping. This is a hard shift.
Took it to indy service, say it has a front seal leak and is low on fluid. I knew of the leak. (Had trans serviced about 60k miles ago)
Recommend a full rebuild of trans, $4,400. OK. After rebuild, still has same shift issue. Says ECU was probably cause of original issue, compounded by low fluid,
recommend a software update to ECU. (no charge) Update did not fix the issue. Now recommending a new ECU, at $1,100, his cost, no upcharge.
I trust this guy, but said if the new ECU does not fix it, I'm not paying for that. AITAH?
Anyone have an issue like this, and had it resolved? With the new ECU, I'll be in it for 9K! I also had the timing belt, water pump, radiator, front and rear main seals,
lower control arms bushing, ball joints, power steering hoses replaced. But I love the car, hoping it would be like new again.

Thoughts?

 

This is a known issue with our cars
Look at this thread
https://www.clublexus.com/forums/ls-...nt-to-sia.html

Since you're in CA, you can check this place out
https://stores.digitalautotech.com/l...epair-service/

You don't need a new ECU.

 

@Stevequad , yeah, what @LatinLS430 said. I can see you're newer, so a tip is to run your searches through Google, not the internal tool; it's not very good. In addition to the mention above, if you Google "clublexus LS430 transmission", you will get some threads. You do NOT need to spend anywhere close to a $1000 to fix this.

 

It's the soldering crack issue caused by the heat cycle in the engine compartment room. The repetitions of hot and cool down causes the soldering crack to some of components. Most of those are T900, T901, D903, D901, D905, D906, IC901, IC903, R910, R912, C724, C901, C771, C103, D711 or R839. One or some of these causes the soldering crack. A person who is familiar to soldering can fix the problem using a good magnifier carefully observing the ECU board. Even a person who is not so, re-solder these components unconditionally and you probably will be happy.

 

Late to the party - Yes do the ECU first - I got a full rebuild here is FLA for $2700 plus I had to send out my ECU to SIA for another $240 ( with shipping) Mine is sorted out now - 2004 with 160k and no hard shift into drive or hunting for the upper gears. Did you get this sorted out? https://siaelec.com/

 

what is the goal here?
museum piece or daily driver.
daily driver you should be good... enjoy
museum piece you would need tie rod ends and sway bar bushings, lots of other stuff that will make very little difference, did you do motor mounts?

 

10/4/25
No, it is not fixed yet. Had a full rebuild on the transmission, and waiting for the new ECU to arrive. I did not do any of it myself. I'm 78, still in pretty good shape, except for a bad back. Replaced radiator, hoses, power steering hoses (check the price on those), timing belt, water pump, tensioner, front and rear main oil seals, lower control arms, bushings, ball joints, struts, Trans and ECU. All for the low low price of $9k. car has 195k miles on it. I was going to buy a new Lexus, but that would have taken all of my mad money. The car would only be worth 9 to 12 k on a good day, so we decided to just get it fixed up. It is a wonderful vehicle, and..the devil I know.
The shop that is doing the work is a well respected indy in our area.

 

Jffgry706:
I did motor mounts at about 120k miles.

 

Sounds like you got yours sorted out - goodluck

This menu you have sounds like my 160k -

• Replaced radiator,
• hoses,
• timing belt
• SIA ECU fix
• Transmission rebuild
• restored interior
• replaced all speakers
• To Do List
• replacing LCD to brand new Toshiba 7"
• front end still needs about $1500 worth of parts and labor
• Fixing tint and installing clear UV front windshield
• Needs alignment after front end work
• Needs fresh set of tires
• Refresh rims OEM
• Stevequad says 120k motor mounts - I haven't checked mine yet. 160k

Is it worth it? Heck yeah but I am upside down on this unit but don't care -
Today just took it on the turnpike into Ft. Lauderdale U-Pull-It junkyard and scored a few parts - she runs good even with bad upper ball joints - very smooth ride.
I say it's a keeper

goodluck
H.

 

It's all fixed, and feels great. Now on to my next issue...

 

Who fixed your ECU?

 

Yo - way to go - may we all get many miles ahead

 

My baby succumbed to the dreaded hard downshift last night. I shipped out the ecm to SIA this morning. OP glad yours is running right now!

 

I had the exact same problem. I used this write up to help diagnose the problem after struggling with oscilloscope measurements of solenoids S1 to S4, SL1, SL2 and SLT with no luck. There were just no anomalies on these signal lines for a constantly repeatable failure condition!

IC907 appears to be the culprit. I used my oscilloscope and soldered wires to the ECU to get to root cause. I used S1 as my trigger (wiring harness E pin 19) when shifting from second to first gear. I probed wiring harness E pin 13 at the ECU (SLU+) to determine if the lock up solenoid was changing when I slowed from second to first or accelerated from first to second when driving. The voltage was a constant 0V no matter what the driving conditions were, even at 60 mph. I didn't think to check this line because the lockup solenoid isn't supposed to kick in until 45 or so mph, and this problem is shifting from second to first mostly. The linked write up reminded me of the transmission power flow and that I'd best scope it. SLU+ (pin 13) to SLU- (pin 12) turned out to be the problem. No matter the driving condition, T901 drain always stayed at 0V. Since there are no pinouts for the gate or source for T901, I soldered wires to each to see why T901 was never changing from 0 to 12V. T901 and it's flyback diode were just fine per a multimeter diode check. I then disconnected wiring harness E and put battery voltage across pins 13 and 12 (SLU+ and SLU-), and the lock up solenoid triggered. 12V on the source of T901 was rock solid. Thus, no electrolytic caps had failed (C724, C901, C103). This is extremely unusual for me. Power components are ALWAYS taken out first usually due to an inductor failure. HOWEVER, in this case the signal line (pin 5 from IC907) driving T901 would never drive the gate of T901 to 0V thus activating the P channel MOSFET. The gate of T901 would only stay high at 12 V and thus, the lock up solenoid could never engage.

I dismissed the idea some folks had claiming the repair requires a firmware update. If that were the case, then one of the large gate arrays has failed, it has to be replaced with another proprietary one, and those aren't available for sale to the public. Thus, this claim just didn't hold water with me. If the firmware gets corrupted, the gate array must be replaced. Broken solder joints and failed components was logical. I wish I'd used my normal troubleshooting process. So much reflowing via hearsay is a WASTE OF TIME. Get to root cause with a scope, follow the power flow diagram, and you'll get to the solution in a timely manner. I wasted a couple of days reflowing and testing those other solenoids. UGH!

Since there have been so many failures with this same condition (hard downshift from 3rd to 2nd and worse from 2nd to 1st suddenly), it got me thinking that even though reflow solves many problems, this chip might be a weak link. It's SE619 made by Denso and costs around $30. It's a 92 pin IC so a hot air station should do the trick.

For those wanting to understand the problem rather than just sending out your ECU for repair, I hope this missive helps in your diagnosis. That thoughtful person who did the write up helped me understand my ECU problem, and I believe get to root cause.

 

Sounds like you bench a few electronics - interesting post. I have fixed tech stuff for a long time and can get around at component level with my soldering station but I would never call myself a pro. If I get a chance and get an ECU to crack at the junkyard it would be interesting to see the board. Every LS430 that hits any yard here locally get picked over immediaetly unless your in the yard and they drop the unit in. Did you reflow any solder? Just curious.