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A number of people have talked about their need (or want) to reset their car's ECU so their engine and transmission can relearn their personal driving characteristics. Below is a link that will help you accomplish resetting your ECU.
The engine control unit, or ECU, is basically the brains of your car. The ECU stores diagnostic trouble codes when it senses a malfunction so a mechanic can fix it later. It's also the ECU's job to store your driving data to customize your ride. For around the first 1,000 miles of the ECU being reset, the car adjusts to the driver's typical driving style. The transmission will try to go to a higher gear more quickly if driven constantly with a light foot. Conversely, if driven with a lead foot, the transmission will try to hold a gear longer for better acceleration. Resetting the ECU can help re-tailor the car to your liking. There are a few different ways to reset the ECU; the three main options are covered in the link above.
► Note: If you use Option 1 (Disconnecting Battery): It is recommended that you press the horn (for up to 30 seconds) to fully discharge any stored voltage in the capacitors from which memory can be retained.
The ETCS Fuse (Multi-port fuel injection system/sequential multi-port fuel injection system) is located in the Type A fuse box in the engine compartment: Fuse # 24 (10 Amp)
The EFI Fuse (Multi-port fuel injection system/sequential multi-port fuel injection system) is located in the Type B fuse box in the engine compartment: Fuse # 5 (25 Amp)
After 16 years of Lexus ownership (and before that Volvo, Honda, Toyota, Ford, Nissan, VW and Opel), I have yet to see anything from Lexus or Toyota confirming that our transmissions and/or throttles “learn” or “adapt” to our driving habits. All I’ve seen in the Internet is hearsay, conjectures, or faith in enthusiast forums such as CL. An adaptive transmission and/or throttle would be brilliant marketing fluff (think “AVS” in our current 4GS’s) but so far Toyota has been supremely silent on the issue.
If the car’s acceleration or shifting pattern doesn’t feel right, it’s because something isn’t right. A long time ago I wasted a lot of time “resetting” the “adaptive” transmission and/or throttle in my former 2001 GS430 by following threads such as this one and disconnecting the battery for arbitrary amounts of time, then standing on my head and turning the key with my left foot while pressing the trunk release button with my right index finger. I felt really stupid because no matter what I tried, the "resets" never changed a thing. I finally took the car to the dealership and after a lot of troubleshooting, they found a faulty accelerator pedal position sensor. Once replaced, I finally felt the glorious revelation of that V8, and I was glad the transmission and/or throttle didn’t “learn” a damned thing.
There are people who firmly believe that 87-octane gasoline will ruin their stock naturally aspirated Toyota engines, or that a certain brand of engine oil palpably affects their cars. It appears that there are also people who firmly believe that our cars learn our driving habits, so that our bad habits then ruin the driving experiences of everyone else, like our spouses, future owners, and other drivers in a rental (or dealership) fleet. I just don't buy that car makers are that dumb (except GM).
A lot of people question the ECU's ability to [so-call] 'learn' a driving style. That's kind of a stretch! Probably a better way of putting it is - the ECU 'adapts'. The ECU is constantly and continuously adapting to input from various engine-related sensors based on the engine's recent use, which has a lot to do with the driver's driving style. Ummm...so maybe the ECU does have the ability to learn a driving style!
When resetting the ECU there is a segment of memory that will get cleared-out by eliminating voltage to memory chips. This particular segment of the ECU holds data for fuel mapping, airflow, etc. based on the various engine-related onboard sensors providing engine performance and efficiency information back to the ECU, which is ultimately established by how the engine has been used and asked to perform recently. Call it your driving style if you wish, or call it adapting to recent use, or call it some other description - but the ECU is continuously updating data and averaging this data to electronically tweak how fuel and air is best delivered to the engine based on its recent use. So, as you can probably guess, unless you floor the car from every stop, and constantly drive 100 mph, that memory will eventually get populated by a comprehensive representation of your 'overall' driving style.
If you always drive conservatively and never really give it too much throttle (rarely putting much load on the engine), and don't go much above the speed limit, then you will end up with an ECU map that simulates this. On the other hand, if you always have your foot 'in the gas', you will end up with a more aggressive map. If you have a conservative map, the car might seem slower to respond (under less than WOT conditions) if you do want to 'get on it', and vice versa.
With the Lexus Sport/Sport+ modes the mapping is purposely changed to enhance performance at all throttle input levels. However, at wide-open-throttle (WOT) in any drive mode, including ECO, the mapping changes to maximum performance. Some people say they don't notice any change after resetting the ECU, some say it is quite noticeable - so it all depends on what mapping you had before you reset it, and whether you are testing it at less than WOT, and which drive mode you are in...as well as your seat-of-the-pants sensitivity to change. There's one thing for sure - the ECU is still going to be constantly and continuously updating and adapting...so your highway cruising at a constant 2,000 rpm or idling in stop-and-go traffic, and waiting on stoplights to change will bring the ECU right back to your 'overall' driving style.
After resetting the ECU - is an engine more responsive or less responsive than before the resetting? Well, it depends - it depends on how the ECU designated the mapping (robustly or conservatively, and to what extent) prior to the resetting, which is understood to start fresh with a centrism or middle-of-the-road readjustment. Will resetting the ECU provide a reasonable period of time where the engine is likely to be more responsive, than not? The reset ECU will start immediately to analyse the data inputs, and adjust and adapt to that measure. It could result in entropy or betterment.
Is it worth your time and effort to reset the ECU? No, not really...
How to Reset Your GS 350 ECU
