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What I have discovered in my 2001 AWD is that at the moment of VSC activation I am generally too involved in driving the vehicle to look down at the instrument panel when/as the buzzer sounds. And then by the time I do the "event" is over and there is no indication. I'm relatively sure that at least two or three of the incidents involved understearing so I have concluded that the "squiggly" light comes on with the buzzer but doesn't remain on long enough for the driver to take notice. But to answer you base question... Yes, the RX series is AWD/(4WD) for marketing purposes only. The initial series was natively front torque biased, 95/5 and has a viscous clutch/coupling mounted across the two outputs of the center differential. The idea was that with slippage at the front the VC would tighten up and partially lock the center differential and thereby raise the torque level to the rear. The problem was that the formulation of the viscous fluid was such that it remained flaccid and even if front wheel slippage persisted for an extended period would only couple about 25% of the engine torque to the rear. So in the short term, matters of seconds, it had no drive toque to the rear. In 2004 the VC was dropped, center differential always fully "open" in favor of the use of braking to apportion engine torque front to rear and side to side. In effect the brakes are used to simulate LSDs. Limited Slip Differentials, front, center, and rear. For some reason the torque biasing to the front was also increased in 2004. The problem with that was that while you had virtually instantaneous torque apportionment from the front to the rear if the slippage persisted the engine had to be dethrottled to prevent the brake rotors from overheating and warping. Not just a few owners were at their wits end trying to figure out how to disable the system so wheelspin, or back and forth rocking, could be used to get unstuck. Now I see that for the new RX350 the VC is back in use. Hopefully with a better viscous fluid formulation and an improved method of quickly dispersing the HEAT from the VC once the "event" has passed. And maybe, just maybe, the engine torque is now biased to the rear as it should be, but I wouldn't put money on that. Try, try, and try again, Toyota will get it right sooner or later. In the mean time I'm off to see Acura about purchasing the new RDX as soon as it is available. Dynamic, on-the-fly, torque allocation, 70% to the rear if conditions warrant and as much as 100% of that to the outside rear wheel while turning. Sooner or later the RX series will get the new DFI engine and the absolutely STELLAR GS & IS AWD system. Hopefully sooner rather than later, meantime I'll be enjoying my RDX.

I've been being an idiot! I've been trying to figure out for weeks how Toyota determines that the accelerator pedal is in the fully released, idle, position. I can fully understand how they determine the initial position when the battery is first connected, but how... Then this morning it hit me. You must depress the brake pedal, FIRMLY, in order to shift out of parking gear. If I were the engineer writing the firmware that is exactly when I would most expect the accelerator pedal to be fully released. So, if, drive cycle after drive cycle, the shift from park into a drive range occurs with the gas pedal depressed, even ever so slightly, the engine/transaxle ECU might re-learn, likely adjusting the parameter gradually, the sensor output voltage for the accelerator pedal idle position. The next part you will not believe. I NEVER use my left foot for braking.. WRONG! My RX is always parked "nose in" into the garage. This morning I used my left foot to brake while I started the RX and shifted into reverse, and continued to brake with my left foot as I backed out of the garage. I know I do not use my left foot for braking in the normal sense and I have no idea when or how I developed the habit of doing it in reverse, or maybe only while backing out of the garage. So, if you have DBW be sure you do not have any pressure on the accelerator pedal as you firmly depress the brake in order to shift into gear. And be mindful of floor mats having inadvertently slipped forward and now laying on the accelerator pedal. Kudoes to user777, to whom I should have listened more closely and who was much closer to this idea than I was.

disconnecting the battery simply treats the symptom and not the cause. Get the codes read and follow a diagnostic flowchart to determine the actual cause for the lights. Keep in mind the the code produced may not always be the cause either. steviej But..... If you disconnect the battery to kill the indication and the indicator doesn't come back on you can pretty much rest assured that whatever problem there was was a transient one. Like maybe an improper gas tank fill procedure. If it repeats, then worry.

Methinks there is a very BASIC misunderstanding going on about the engine/transaxle delay hesitation. There is the STANDARD delay EVERYONE experiences at one time or another. Toyota is very definitely, by their own admission, using the DBW, E-throttle system, to delay the onset of engine torque developement to "protect the drive train", give the transaxle downshift clutches time to fully and firmly seat. Not any different than any of us would do when downshifting a manual transmission, at least most of the time. This "standard", normal delay, hesitation, is being noticed, noticeable, because prior to DBW our engines's torque began to rise the instant we depressed the accelerator. That's very likely also why the pre-04 RX series is enduring a serious number of premature transaxle failures. ASL= more frequent upshifts and downshifts, no DBW, NO delay = an inordinate level of clutch frictional surface wear. Insofar as I can tell the new automatic transaxle shift logic recommended by Sierra Research in April of 1999 was adopted for the RX before my 2001 RX300 was built. So, let's say that the "standard" delay is on the order of 200 to 500 milliseconds (2/10's to 1/2 a second). That's enough for everyone to take notice, especially those having previously, or still, driving older versions. Now, lets assume that a very small number of accelerator pedal assemblies leave the factory with the "at rest", fully released, sensor output voltage on the high side of the acceptable tolerance, above 0.8 volts, as high as 1.1 volts. First there is the fact that the factory manuals indicate that the low end of the accelerator pedal's "usable" range is with the sensor's output explicitly at 0.8 volts. It makes perfect sense that the designers would want some slack, tolerance, a "widow" (0.0xx to 0.8 volts) of voltage ranges that represent the idle, fully released, position. But now we have some pedals in use by customers wherein the sensor never falls below 0.8005 volts. Why would that matter? Because the transaxle shift control design would not likely upshift if the pedal were fully released. Fully released would be assumed to mean "I wish to coastdown to a lower speed" and upshifting would not be conducsive to that. On the other hand what if you just ease off the accelerator pedal slightly? The logic would be such that the system would assume "I want to just begin cruising along at about this speed", and an upshift would then be very appropriate. And now..... What if a part of the engine/transaxle ECU firmware, due to those flawed tolerances, just simply couldn't detect the difference between a partial accelerator pedal release and a full release. Definitely would have a much greater propensity for upshifting, right? And what other aspects might result from the firmware being "confused" (why is the driver on the gas and brakes at the same time?) in this manner? Maybe a "watch-dog" timer master firmware reset? In effect a engine/transaxle ECU firmware "reboot". How many seconds might that take?

Are we really going back to the use of the VC. viscous clutch/coupling, after only three years of the use of brake apportioning of engine torque? Or like other features is this a Canadian market aspect only?

Can we be sure that Toyota/Lexus actually considers the delay/hesitation a mistake? All I got from the service manager at Lexus of Bellevue about a week ago was his grousing about people being to cheap to use premium fuel. Talk about being totally out of touch with your customer base! Personally I think Toyota is, has been, concentrating on the "standard" delay/hesitation that arises, justifiably, from the new automatic transmission control techniques recommended by Sierra Research back in 99 and not realizing that a significant level, a few, drivers are for some as yet unknown reason expereincing an extended delay/hesitation symptom. Under the new techniques, ASL (Agressive Shift Logic) in particular, these transaxles will be dramatically quicker to upshift on full or even partial, slight, throttle "lift". Obviously that will result in the transaxle being in the wrong gear ratio when/if the driver subsequenctly decides to accelerate. The only advantage I can see for the use of premium fuel is that the downshift selection will/can be more decisive due to less likelihood that the downshift will result in engine knock/ping. If electonic accelerator pedal assembly's output is between 0.1 and 0.8 volts the pedal is assumed to be fully released and the engine will be commanded to idle. "Usable" range is designated in the 2004 Lexus RX330 shop/repair manuals to be between 0.8 volts and 5 volts. Yet the test procedure in the shop manual indicates that the allowable output voltage of the sensor with the pedal fully released can be as high as 1.3 volts and still be acceptable. Does not compute!

The "TRAC-OFF" is a default condition due to any engine diagnostic indication. Your base problem is the engine diagnostic indication. The engine light may have come on due to your failure to follow "proper" gas tank fill-up procedures. To reduce evaporative fuel emissions the gas tank, fuel system, is kept under a slight vacuum. when you refuel that vacuum is lost but the ECU "sees" the fuel level rise and negates the diagnostic pending the fuel cap being reinstalled and the vacuum level again rising. The wrong fuel cap, or removal without refueling, or refueling too little for the ECU to detect (poor student), will oftentimes result in an engine diagnostic just a few miles down the road.

For detailed information on the mould odor go to airsept.com and read up on their EED, elctronic evaporator dryer.

Okay, I have now abandoned the idea of VSC/Trac causing the problem.

It would be unusual, in the extreme, for any 04 Lexus not to at least have Trac, especially a FWD Lexus. Look for a lighted icon, Trac or VSC on the instrument panel just after you turn the ignition on, but not to the start position. Trac: Traction control is a subset of ABS. If the driven wheels start to spin as the result of applying too much engine torque for the surface traction Trac will apply braking to the drive wheels, in your case the front wheels and simultaneously dethrottle the engine. Wheelspin/slip indicates loss of traction and on a FWD vehicle that will mean loss of the ability to maintain or provide directional control and thereby often results in an accident due to loss of control.

It is NORMAL, SOP. I have not yet driven any modern day car wherein the headlight lever doesn't drop slightly at idle. Have you looked at all of the eelctrical load these cars must carry? And keep in mind that the current draw of the ABS pumpmotor is substantial so a lower headlight level then is completely understandable.

I'm not into all this mechanical stuff.. I'm just "a girl". ;-) But my car definitely falls in the 1-2 second, heck I could just say 2 second delay. Yes, there are times I feel this could put me in an unsafe condition. Particularly when in bumper to bumper traffic or times I need to "get on out there" in fast traffic. You don't say if your car has VSC and/or Trac..... And DAMN, I was just in the Palm Harbor area for the entire week following the 24 hours of Daytona!

Ohay, how do you know that there are not two "forms" of engine/transaxle delay/hesitation? One form which Toyota has deemed "normal", to protect the drive train, and a second, extended one, causing delays of one of two seconds are more. I can fully and easily accept Toyota' explanation that there is an intentional delay in allowing the engine to develop a substantial level of torque as the downshift is completing. I often drive a stickshift and I do not wish to be replacing the clutch prematurely. So I am careful to not apply gas inordinately quickly as I engage the clutch after a downshift. So I can fully accept Toyota explanation that the delay is to protect the drive train. But just how long a delay are they talking about? Certainly one that would be noticeable if one were in an especial hurry to accelerate. But clearly, that wouldn't be 1 to 2 seconds as is being complained about, a few hundred milliseconds, maybe. So, ALL of Toyota's electronically controlled transmissions with DBW are exhibiting some level of downshift delay. Enough of a delay that any driver having experience with previous, non-DBW transmissions, will definitely notice when quickly returning to acceleration circumstances. So, what if the anomalous "extended" delay only occurs on vehicles with Trac, or even VSC. Look at the contention between the parties, posters, involved, some say the delay is hazardous. In my opinion a 1 to 2 second unpredictable delay might very well put one into an unsafe condition. But many who claim to be experiencing the delay contend "no way" to the unsafe or hazard issue, and often further dispute the 1 or 2 second amount. Good, logical evidence that there may be two forms of the delay/hesitation.

Trouble-shooting involves opening one's mind to ALL possibilities. Many modern day vehicles have some version of Trac (traction control) an off-shoot of ABS. Basically if the car develops wheelspin/slip as a result of too much driving torque on whichever wheels the engine is coupled the Trac system will apply brakes, moderately, to the slipping wheels. On a RWD vehicle Trac will immediately apply moderate braking to the driven wheels but give the driver a few hundred milliseconds to realize what is happening and take corrective action by feathering the throttle. On a FWD vehicle wheelspin/slip at the driven wheels, the FRONT wheels, is so much more hazardous that the driver will get no time to react, the engine will be dethrottled simultaneously with moderate braking. Remember that if the driven wheels on a RWD vehicle begin to spin due to loss of traction you will still have the entire front tires' contact patch to regain or maintain directional control with. On a FWD vehicle your driven wheels are also used for directional control so preventing even a slight period, a few hundred milliseconds, of loss of traction there is much more important. The dethrottling of the engine, regardless of drive type, is to prevent over-heating and subsequent warpage of the brake rotors.

"....move on to something else...." Okay, what about the Trac firmware, or even the ABS firmware having a flaw? In almost all instances described in the TSB it is highly likely that the driver just removed their right foot from the brake pedal to the gas pedal.

Okay, so what's the harm in trying..?? My 2001 RX300 owners manual indicates that Trac was standard on 2WD and VSC on 4WD vehicles. In any case it looks as if the procedure will also disable ABS/Trac/BA/EBD so who's to say it isn't one of these other braking related control functions.

The service manager at Lexus of Bellevue told me that the really simply way to disable VSC temporarily was to create an engine fault. So I disconnected the MAF/IAT sensor connector on my 2001 AWD RX300 while the engine was running. The engine died almost immediately and wouldn't restart. When I reconnected the MAF/IAT it started right back up but with an engine & VSC failure indication. After about 4 drive cycles the indications went out. So for any of you that are experiencing the extended delay/hesitation symptom if you want to try and see if VSC is somehow related.....

I'm not reading that whole post, but why then does the ES without trac or VSC have the same delay? I don't think anyone has sold an ES series since 2002 without VSC....

Acknowledgements: Toyota has now publically announced, admitted, that there is now an inherent delay in downshifting their electronically controlled transmissions and transaxles to "protect the drive train". You would not typically engage the clutch with a stick shift before moving the shifter into the "gate", selected gear position. Toyota's automatic gearbox is now preventing the engine from developing torque until the transmission's internal clutches for the selected gear ratio are fully and firmly seated. This post does not concern, does not propose to address, the "standard" transmission shifting delay as disclosed by Toyota. A relatively small number of Toyota and Lexus owners, encompassing model years 2002 through 2006, are complaining about extensive downshift delays. These complaints seem to primarily involve FWD vehicles or AWD vehicles with definite front torque biasing and 5-speed transaxles. This post will focus on just what those few owners might be doing, or not doing, during the operation of the vehicle that might lead to an extended downshift delay period of 1 to 2 seconds. Technology, ain't it wonderful? BA, Brake Assist: Just what is this? Apparently via studies by the automotive industry at large it was learned that some of us are not using our brakes correctly, at least not in all instances. As I understand the implementation, design, in an emergency or panic braking circumstance some drivers apply the brakes quickly, but for some unknown, unknowable, reason then just as quickly slack off the pedal. This might be due to reacting to, being unfamilier with, the resulting pulsations from ABS actiavtion, or it might be a "learned" reaction. Before the advent of ABS many drivers "learned" that severe, hard, brake application would often result in loss of vehicle control. So the industry decided, on its own, that many of us would be better served if "they" did the "driving", at least in this instance. Basically BA "watches" the rate at which we apply pressure to the brake pedal. If the brake pedal "stroke" is rapid/quick but then brake pressure slacks off quickly then the BA function is activated and HOLDS the brakes into a heavy application for some predetermined period even with the driver having slightly backed off of the brake pedal pressure. I may be somewhat wrong about BA in the above dessertation by the important point, aspect, is that BA is being triggered by the "rate of brake pedal travel/activation". Porsche 997 EBD, Extended Brake Assist: Same as above but with one added feature. The processor "watches" the rate at which the accelerator pedal is released. If you lift the accelertor pedal rapidly then the system presumes (second guesses??), that your foot is now headed for the brake pedal and "pre-charges" the brake fluid pressure to move the brake pads from their otherwise retracted position and into "slight" contact with the rotors. So, we now know that the Toyota/Lexus BA, Brake Assist, system is watching the brake pedal rate of travel to determine if brake assist should be activated. And we also know that Porsche is watching the rate at which foot pressure on the accelerator pedal is removed. So, given the above as factual, is it really so outlandish to think that the Toyota/Lexus drivers who are experiencing these extended downshift delays aren't somehow, in some fashion, causing these results? I can tell you truthfully and frankly that my 2001 AWD RX300, when I'm trying to stop on a very slippery roadbed surface just plain does not want to come to a full and complete stop. The anti-lock braking system goes absolutely bonkers! The slower the vehicle speed declines in this circumstance the "busier" the anti-lock systems becomes. But frankly, that's exactly the way it should operate, allowing me to maintain directional control right down to the lowest IPS (inch per second) travel rate. But what would happen if I suddenly slipped the transaxle into 1st gear? The idle engine speed would likely provide enough engine compression braking to overcome the ABS activity. And that latter is exactly one of the aspects VSC protects you from. If VSC detects understearing on a FWD vehicle it will quickly act to alleviate engine driving torque and prevent engine compression braking. Why would rapid release of the accelerator pedal, or rapid release of the accelerator pedal and then quick application of the brake pedal "falsely" trigger a VSC activation? Or for that matter since the ECU in which VSC functionality is embedded is the "Skid Control ECU" and therefore handles all of the brake control functions, ABS/BA/Trac/VSC/EBD, might not a false activation of any of these functions be the cause? Porsche is asuming that rapid release of the accelerator is a likely indication of quick subsequent brake use. What if we follow that tract and see where it goes? We already know that at extemely low speeds on a slippery roadbed engine compression braking can overcome the ability of ABS to keep the front wheels rolling. So suppose Toyota is preventing shift-downs and/or maybe even commanding upshifts in the same circumstances and for the same reasons Porsche is precharging the brake pistons? Just a couple of side issues. Between 2001 and 2004 Toyota moved the two VSC sensors, stearing wheel position sensor and yaw sensor, from a direct connection to the skid control ECU to connection via CAN, Controller Area Network. In 2001 all network communications was via the proprietary BEAN, Body Electronic Area Network. That might mean that Toyota (or Denso) is no longer in control of the VSC functionality. Bosch, maybe? When I traded in my 2000 AWD RX300 for the 2001 AWD RX300 I did so primarily to get VSC and HID. I was told at the time that a new feature of trac was to provide a virtual form of front and rear LSD, Limited Slip Differential. I remember wondering at the time that if that was so, brake apportioning being used as a front and rear LSD, then why hadn't they just gone ahead and eliminated the VC, viscous clutch, and used brake apportioning for virtual LSD implementation for the center differential? They did! Over the intervening years and the 50,000 miles driven I have come to the firm belief that the brakes are being used to apportion torque front to rear. Very early on I discovered that the VC was almost always "flaccid", almost never stiffened up enough to couple any significant level of engine torque to the rear. On a 4 wheel dyno it took 20 to 30 seconds before the VC stiffened enough to provide ~25% of the engine torque to the rear driveline. All that is my way of saying, proposing, that there are, may be, implementation aspects of the RX330 engine/transaxle ECU and skid control ECU that are not advertised/published. Just this morning I asked the service manager at Bellevue Lexus if the there was a method for disabling VSC. His immediate response was "publically available??". And then went on to explain that the one published (disclosed) in AutoWeek worked. And even after I learned of the existance of several of the unpublished C-best options available for my 2001 RX300 the dealer denied their existance until I came back with a printed copy. So, what if a portion of the Trac firmware is "watching" the rate at which you release the accelerator pedal and, like Porsche, is somehow preparing the system for a subsequent brake application? How many of you, given a stick shift on a FWD vehicle, would use engine braking to slow the vehicle if you weren't certain of a high level of roadbed traction? And what about downshifting a FWD vehicle for slowing? What, no volunteers?? No insanity out there, none? What if that is exactly what is happening with the owners that are experiencing the extended downshift delay? The Trac system is not allowing downshifts if it expects a quick, following, brake application.

That wouldn't possibly be related to the fact that the majority of cars on the market today (especially Toyotas) are FWD? True, but.... Toyota, having adopted the fuel saving features recommended back in 99 by Sierra Research, would have applied it across the product line, Toyota, Lexus, FWD, RWD, AWD and 4WD. I haven't been able to find even one complaint for the nature of the problem as described in the TSB in any Toyota Vehicle other than those with FWD or front biased AWD. And keep in mind that when VSC is active it assumes control of the throttle valve and the transaxle to prevent or delay downshifting. The two complaints common to the hesitation symptom are delayed downshifts and engine acceleration delay. Let's for the moment assume that the VSC system falsely thinks the vehicle is under-stearing/plowing. Remember that under-stearing/plowing most commonly occurs on FWD vehicles when the front tires' roadbed traction coefficient is too low for the combined forces, lateral (directional control) and braking or acceleration. Obviously there would be two versions of the VSC firmware, one for FWD and one for RWD. Since under-stearing is so highly unlikely in a front engine RWD vehicle might it be totally ignored? But even if not totally ignored how high might the triggering "moment" be set? But under-stearing on a FWD vehicle is highly likely, much more likely. If the vehicle is under-stearing/plowing, not following the direction "set" by the front wheels, how do you control/adjust the vehicle dynamically to devote the absolute maximum front tire roadbed traction to lateral control? You neutralize the engine drive/lag torque by assuming control of the throttle and matching engine RPM to roadspeed based on the current gear ratio, and obviously you cannot allow any pending downshifts. In the case of my 2001 RX300 it actually applies the brakes to both rear wheels on the assumption that whatever roadbed traction might be remaining at the rear can be used to slow the vehicle and thereby help regain traction at the front. Over-stearing......?? Rare event for FWD, VERY rare event! And remember that with a RWD vehicle in over-stear one very likely still has the entire level of front tire roadbed traction to devote to directional control/recovery. Looking back on my 50 years of driving I cannot think of even one instance wherein an unintendional or inadvertent skid, over-stearing, wasn't the result of too much engine torque at rear end. I can only think of one instance wherein my lifting of the gas pedal and/or releasing the clutch didn't quickly result in a skid recovery. That one instance was the result of inadvertently and unknowingly have cruise control engaged (below my actual road speed of the time) on an ice and snow covered roadbed. Under-stearing.........?? Rare event in a RWD vehicle but common to FWD. I can only think of one time and that was in the rear engined 78 Porsche 911. My 2001 AWD RX300 has threatened to under-stear a few times but that was quickly overcome by VSC activation in each instance. So, were it YOU designing the VSC firmware for Toyota wouldn't you make the FWD version "hair-thriggered" as pertains to under-steering? And the RWD firmware "hair-triggered" for over-steering"? And just mighten that "hair-triggering" cause exactly the hesitation symptom drivers of FWD or front biased AWD are reporting? Might you even have a "pre-emptive" firmware routine to help alleviate top heavy SUV rollovers? How would you do that? Prevent the driver from accelerating into/through a tight turn... No high engine torque production and/or not downshifts to apply additional torque for acceleration.

I disagree. There are many complaints about this downshift hesitation on FWD (I think he meant RWD) also, so this negates the theory of under-steering or over-steering causing these problems. In fact, I was driving my brothers '05 LS430 recently and I could replicate the hesitation as I had on my '03 Es300. "....clear majority....." I didn't say, haven't said, that the problem doesn't occur on RWD vehicles, just that complaints of this type are rarely posted for RWD. So I stand behind my theory for the moment.

I'm not saying these are circumstances wherein VSC should activate, just theorizing that due to some design flaw and/or sensor miscalibration it is (partially, briefly??) activating. Yes, there is supposed to be a buzzer sound and an indicator light if VSC activates. But again, what if it's activation is the result of some sort of firmware design flaw that is enabled by one of the two sensors being slightly out of calibration? I can easily miscalibrate, and will, either of these sensors on my 2001 AWD RX300 but I don't expect to learn anything since my 2001 isn't DBW and therefore doesn't seem to be subject to the problem.

A CLUE...... IMMHO most, or a clear majority, of the complaints of engine/transaxle downshift delay/hesitation in various forums all over the internet seem to involve only the FWD or front biased AWD versions of the Toyota and Lexus 5-speed vehicles. The shop manuals tell us that if the VSC activates it assumes control of the throttle and the transaxle shifting sequence. The VSC only activates, really, if it detects over-stearing or understearing. When it detects under-stearing, "plowing", it applies the brakes to both rear wheels (at least for the RX300,330), on the assumption that slowing the vehicle even slightly might allow the front wheels to regain enough traction to alleviate the condition. For over-stearing it modulates the braking of the outer turning wheel according to the severity of the level of over-stearing. As one can then see, the result of VSC activation and assumption of the throttle and transmission shift sequence might be entirely different for a FWD drive versus a RWD vehicle. UNDER-STEARING: When a RWD vehicle is understearing some level of engine compression braking at the rear, DRIVEN, wheels might even be desireable. Whereas on a FWD in an under-stearing situation engine compression braking on the wheels already having lost traction would be highly undesireable. Obviously allowing a downshift on a FWD vehicle during this situation might even lead to total loss of control. OVER-STEARING: To correct and help recover from over-stearing the brakes are applied to the front outside wheel. If the driver happens to be braking during the incident the VSC will actually release some level of braking at the inside front wheel. The VSC activation will likely prevent all engine compression braking or even acceleration torque by modulating the throttle to match engine RPM to road speed. Obviously any impending downshifts would be delayed until the situation has passed. So, for me, there is now enough information available to conclude that for whatever reason the VSC is activating, just ever so briefly, and causing these incidents of engine/transaxle shift delays. Under-stearing, plowing, is much more common on a FWD vehicle, while over-stearing is more common on RWD vehicles, often the result of a too heavy throttle application. So which driver is most likely to notice, let alone complain, about inadvertent and brief VSC activation and the resulting loss of throttle control and delayed downshifts? And keep in mine that as you drive around that corner the front wheels are turning at a different rate than the rear and the outside wheels are turning faster that those on the inside of the turn. So if the VSC is somehow faulty (lack of sensor calibration or tire inflation disparity) and always on the "cusp" of activation accelerating around that turn would certainly trigger VSC.

A CLUE...... IMMHO most, or a clear majority, of the complaints of engine/transaxle downshift delay/hesitation in various forums all over the internet seem to involve only the FWD or front biased AWD versions of the Toyota and Lexus 5-speed vehicles. The shop manuals tell us that if the VSC activates it assumes control of the throttle and the transaxle shifting sequence. The VSC only activates, really, if it detects over-stearing or understearing. When it detects under-stearing, "plowing", it applies the brakes to both rear wheels (at least for the RX300,330), on the assumption that slowing the vehicle even slightly might allow the front wheels to regain enough traction to alleviate the condition. For over-stearing it modulates the braking of the outer turning wheel according to the severity of the level of over-stearing. As one can then see, the result of VSC activation and assumption of the throttle and transmission shift sequence might be entirely different for a FWD drive versus a RWD vehicle. UNDER-STEARING: When a RWD vehicle is understearing some level of engine compression braking at the rear, DRIVEN, wheels might even be desireable. Whereas on a FWD in an under-stearing situation engine compression braking on the wheels already having lost traction would be highly undesireable. Obviously allowing a downshift on a FWD vehicle during this situation might even lead to total loss of control. OVER-STEARING: To correct and help recover from over-stearing the brakes are applied to the front outside wheel. If the driver happens to be braking during the incident the VSC will actually release some level of braking at the inside front wheel. The VSC activation will likely prevent all engine compression braking or even acceleration torque by modulating the throttle to match engine RPM to road speed. Obviously any impending downshifts would be delayed until the situation has passed. So, for me, there is now enough information available to conclude that for whatever reason the VSC is activating, just ever so briefly, and causing these incidents of engine/transaxle shift delays. Under-stearing, plowing, is much more common on a FWD vehicle, while over-stearing is more common on RWD vehicles, often the result of a too heavy throttle application. So which driver is most likely to notice, let alone complain, about inadvertent and brief VSC activation and the resulting loss of throttle control and delayed downshifts? And keep in mine that as you drive around that corner the front wheels are turning at a different rate than the rear and the outside wheels are turning faster that those on the inside of the turn. So if the VSC is somehow faulty (lack of sensor calibration or tire inflation disparity) and always on the "cusp" of activation accelerating around that turn would certainly trigger VSC.

2004 RX330 electrical wiring diagram Pub. No. EWD563U page 177. (Quote) "4. Mutual System Control To efficiently operate the VSC system at its optimal level, the VSC system and other control systems are mutually controlled while the VSC system is being operated. Engine Throttle control. The engine power does not interfere with the VSC brake control by controlling the opening of the throttle and reducing the engine output. Engine control and electronically controlled transmission control. The strong braking force does not interfere with the braking force control of the VSC system by turning off the accel. and reducing changes in the driving torque at shift-down." (End quote) As one can readily see from the above statements the inadvertent operation of the VSC system can result in engine dethrottling and delayed downshifts. If the VSC detects over-stearing it will apply, modulate, the brakes on the outer turning wheels. The greater the degree of over-stearing the harder that outer front wheel will be braked. On the detection of under-stearing it will apply both rear brakes (RX330 only??) while controlling engine power. Notes: "The engine power does not interfere with the VSC brake control by controlling the opening of the throttle and reducing the engine output." Take notice that this statement does not necessarily mean that engine power is reduced to idle. It may mean that engine power is "set" to match road speed, no acceleration torque nor any compression braking. "The strong braking force does not interfere with the braking force of the VSC system by turning off the accel...." ...turning off the accel.... I take it this means opening the firmware control loop between the gas pedal (accelerator) and the throttle valve. Therefore I take this to mean, again, that the engine throttle control is taken over by VSC to prevent any significant level of engine compression braking. "...and reducing changes in the driving torque at shift-down..." Wouldn't this mean delaying down-shifts until the VSC ceases operation? Since for most of the vehicles exhibiting the hesitation/delay the "outer turning wheel" is also one of the two driven wheels, or as a minimum for AWD one of the two primary drive wheels it is no surprise. I think we already know that the VSC system firmware has a proactive mode wherein it dethrottles the engine to alleviate the potential for rollovers in an accelerating and/or tight turn. So, what might make it, the VSC system, think it needs to "operate" just before coming to a full stop or just as you decide to downshift for acceleration. An unequal rotation rate at the driven, front, wheels versus the rear, that's what! Would those of you experiencing this problem please, if you don't mind, check and be sure all of your tires are equally inflated. Maybe even a pound or two extra in the front since the majority of the weight is there? Remember that if you adjust the pressure you will need to "normalize" the new tire pressure levels.