MonkeyRX fixed this problem with an ECU flash (firmware update). Has anyone else had the same success with just an ECU flash update?

Our 2006 GS 300 has 135K and recently started experiencing this same jerk/jolt/clunk harsh downshift while slowing to a stop. The transmission has never been serviced. I took our GS to my regular independent garage in Oakland, California. Our mechanic is good and I trust him, but he is not a Lexus expert. He did diagnosis and found 3 codes: PO138 Oxygen sensor, PO158 Oxygen Sensors, and PO756 shift solenoid B performance S2. Did the following:
1. Flashed computer to update, cost $200
2. Replaced S2 solenoid
3. replaced transmission filter and fluid
4. new gasket

Total cost was $1,100. Unfortunately this did not fix the problem (just one day of driving post fix so far). Mechanic said problem goes away when car is driven in "limp" mode (computer not controlling the transmission). He said that means the problem is the ECU, not the transmission.

This thread also seems to indicate the real fix for this problem is to replace the ECU. Online cost for the ECU ranges from $1K to $1,200. What is a reasonable cost to install the ECU?

MonkeyRX fixed this problem with an ECU flash (firmware update). Has anyone else had the same success with an just ECU flash update?

Also, is it crazy that the transmission fluid and filter does not have to replaced at any certain mileage? It does not seem to be on the service schedule.

Thank you all!
OTbruce

 

Somebody mentioned Lexus has a TSB (technical service bulletin) for this harsh downshift problem. How can I find such a TSB online for this? Thank you,
OTburce

 

To all,
I have a few posts that may relate to what you are experiencing here. First and foremost, TUNEUP!! A proper tune-up from a good mechanic that's been around a while and understands engine to transmission concepts and design. He (or she) will tell you that 90% of repairs are simple troubleshooting and that leads to simple repairs.
I stress a proper tune-up because you most definitively will need to restore as much power back in to the engine as possible. Also, proper engine temperature plays a huge roll in all of this (10 degress too cold makes all the difference in how the car shifts and performs.).
What I mean by a proper tune-up, is spark plugs and spark plugs that are GAPPED correctly. Forget about what is read on the "internet", it’s a fallacy that plugs do not require gapping.
One of the replies here said that plugs were changed in 30,000 and as a result there was a 3 MPG increase. Well, that makes perfect sense if the original plugs were not gapped correctly and the new were closer (he or she got lucky). More than half the plugs I pull from OEM boxes are so far off, I wouldn't stick them in my lawnmower. Stock gap is .044, my car loves .046, which brings me to my point. I experienced
shift points that were off. I performed a proper tune-up, 10 quart trans flush, after which engine (power) sync to transmission was restored, all shift points are now where they should be. So, before you spend senseless thousands, go back to basics, you may be surprised at the results…

 

Stupid problem came back some time ago... was too annoyed to follow up. I guess next thing to try is to replace the ECU. What I don't though is, what the actual problem is? If the ECU unit is defective in our cars, how does replacing it with another used unit fix this problem? Is there a certain year model that works and others that are problematic? Won't we risk replacing one crappy ECU for another?

 

I've had this same issue for a few months now. It's beyond frustrating. I'm just going to trade the car in. Doesn't seem like there's an easy or inexpensive fix for this issue.

 

I was in your same shoes not to long ago...actually 2 weeks ago. I finally fixed the problem to my gs that i had been having for 2 years..... it turns out it was a bad solenoid. I don't know which one was the bad one but I replaced all 9 and damn my car shifts like a dream now.

No more jerk/hesitation and clunk coming to a stop.

 

Which solenoids did you change? How difficult was it to do? Do you have a 2006 GS300 as well? Thanks.

I was just about to post an update. I figured out a cheap way to solve the jolting problem.

When I'm coming to a complete stop, I put the car into neutral right before the jolt occurs. Then when I've stopped, I pop it back into gear. However I do not recommend coasting in neutral. Problem solved.

Now if I can only find a fix for the "Check VSC" issue that keeps popping up. I reset the ECU by disconnecting the negative battery then reconnecting it. It'll solve the issue for a few days but it'll invariably come back.

 

Im not sure which was the bad one. I just replace all 9 of the solenoids in the transmission.

 

 

You don't find the part to just fix the ECU. Send the entire unit to SIA Electronics and explain the specific issues with the transmission, ie. hard 2-1 downshift. They will solder the new part into the TCM of the ECU and send it back to you for installation. It's a little over a hundred bucks for them to fix it.

 

 

Engine bay in the plastic box next to drivers headlight

 

 

Thats because he's a general mechanic not a Lexus guru, and so many people replaced transmission and nothing happened. Then repaired/replaced ecu and it was good.

Get ecu tested, fixed if needed, it's a good chance. I heard many success stories