I have a 2006 with 130K, which I bought about 2 months ago. A mechanic looked at it and felt it was in a great shape. Fast forward a few weeks. So the car runs perfectly fine in every respect EXCEPT . . . when I am on the highway in a stop and go traffic, when the car is moving at no faster than 5-10 mph, the car shifts just hard enough that it gives me a bit of a jolt. Both when the car is shifting down 2-1, as well as when shifting up from 1-2. The car otherwise shifts smoothly so it is very noticeable and bothersome. That's the only situation - I don't experience the issue when I am driving anywhere but on the highway, even with the similar low speed stop and go. Weird.

In noticed this problem before I asked a neighborhood Toyota dealer to do a transmission fluid change as preventive maintenance following my purchase. After looking at it, the dealer refused to do the fluid change because they claimed that they got a code (they muttered something about solenoid c, I believe, but were never clear) and I should go bring it to Lexus. I brought it to Lexus, and they did not find any code nor identifiable issue with the transmission. I test drove with a tech but could not replicate the issue. [btw I had them do a drain and fill 3x, 8 quarts].

After searching here and doing my research, I am considering doing an ECM repair by SIA. The price is right ($130 on eBay) but it will ground my car for a week or so. It's my second car, so I am thinking about it.

Does anyone have thoughts on this? Any similar experience? Should I bring it to a transmission specialist, if Lexus didn't find an issue? Thanks for your help in advance.

 

Hello,

Did you drop the pan and replace the Filter during the flush?

Seems awfully cheap for a proper ECU repair.. Tanin Auto Electronix is a place highly regarded around this forum, I haven't used their services personally, but from sheer number of positive reviews, it would be a pretty solid place to go.

Not sure if it's still a thing on newer cars, but one way to know whether it is a Mechanical or Electrical issue was by disconnecting the pigtail coming to Transmission Solenoids, completely isolating the ECU from the transmission operation, with the trade-off being that now you basically have a manual transmission, and you are responsible for shifting through gears using the Gear Shifter.

See if disconnecting the solenoids will change anything, if there will be a noticeable improvement, the issue is likely somewhere either in the solenoids, or in the ECU, that will take some further diagnostics. Wit that, if it won't make any difference, the issue is likely mechanical, and no amount of ECU rebuild will take care of it, you will likely have to look for a specialist that will be able to diagnose it a lot further.

Hope this helps and best of luck!

 

Before spending any money.......drop the transmission pan and pull shift solenoid SL2 from the valve body.

Inspect the solenoid shaft for signs of damage. If you see damage....replace it.

​​​​​​If no obvious damage is seen, test the solenoid ohm resistance. The resistance should be between. 5.0 and 5.6........if the ohms resistance it's not within these numbers, replace it.

If the ohm resistance is within acceptable limits.......

Swap shift solenoid SL2 with shift solenoid SL4 and see if the hard shift moves from the 1-2 shift event to the 2-3 shift event.

SL2 and SL4 shift solenoids are identical parts.

If shifting between 2nd & 3rd gears becomes hard after swapping solenoids, replace the bad shift solenoid.

SL2 solenoid has orange & black wires.
SL4 solenoid has green & black wires.

If hard shift in 1-2 gears still occurs after swapping solenoids, you may.....
#1 Need new valve body.
#2 Need computer programed.

If you have a way, you can look into the bore where shift solenoid SL2 resides and see if there are any scratches within the bore surface. If there are scratches you will need to replace the valve body or have it rebuilt.

Edited to include:

I almost forgot......if the hard shift remains the same at 1-2 after swapping the SL solenoids..........you can remove and test the SLT solenoid for ohm resistance. It too, should have between 5.0 and 5.6 ohms resistance. .....replace it if it's not within those numbers.

I'm trying to remember how many solenoids there are...........oh well, doesn't matter.......there are three different size solenoids. Let's call them Large, Medium and Small, ok? The SLT solenoid is one of the medium size solenoids and it will have grey & black wires.

The SLT solenoid controls transmission fluid line pressures. The line pressures change depending on calculated engine load, engine rpm, vehicle speed and blah, blah, blah.......this could very well be the reason for the hard shift at low engine speeds.

Take the car to a transmission shop and they'll 1,000% tell you that you need to replace the transmission. Those shops don't FIX transmissions @ $200 per hour. They sell you a $3,500 flat-rate transmission job.

Think about it, if a shop charges $200 per hour and it takes 8 hours to fix a transmission, the shop makes $1,600 that day.........on the other hand.....in the same 8 hours......selling & installing TWO new transmissions the shop makes $7,000 that day.

Good luck.

 

what would cause scratches inside the valve body orifice?

 

The valve sliding inside it......it just happens oner time if trans fluid gets junk in it's fluid from the clutch packs.

 

Thank you, guys!

 

took my LS to a transmission shop because there was a day where I lost reverse... and this is literally what I experienced. $3500 quote because "everything is wrong with it". told them no, car still driving fine. going to do an ECU repair next

 

I have a 2006 and ran into the same problem - no diagnostic codes. I had the dealer send the ECU for repair - apparently the the board had solder failures and was fixed.
Dealer reinstalled the ECU and it is working fine.
You may want to look at the threads describing the ECU repair - there are are places like SIA electronics, where you can send the ECU for repair (not a recommendation!) https://siaelec.com/

 

If you don’t mind me asking, how much did you have to pay the dealer for the repair and reinstall? A Lexus dealer, I presume? How long for a turnaround? Thanks!

 

Here is the info:

Total cost was $ 660
Yes it was a Lexus dealer - Long time customer with excellent relationship (might have given me a discount)
Total time = 1 week
Hope this is helpful

 

Thanks, sounds reasonable as far as stealers are concerned. They probably send it out to SIA or a similar company.