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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.

Go to airsept.com and purchase their EED, electronic evaporator dryer. Google for: nippondenso demist

Back in 1999 Sierra Research Inc, an industry consultant to CARB made three recommendations concerning automatic transmission control systems that would likely result in a 9.8% improvement in fuel economy and therby significantly reduced emissions overall. 1. ASL, Agressive Shift Logic. Assign high priority to upshifting the transmission into the next highest gear ratio as soon, as quickly, as possible given the current roadspeed but without incurring engine knock from lugging due to low engine RPM. 2. Shift the transmission into neutral at all times with the engine RPM at idle (not enough roadspeed to "drive" the engine above idle) and the brakes applied. 3. Early O/D clutch lockup. If/when feasible lock-up the O/D clutch in lower gear ratios other than O/D. By 2001 Toyota had adopted all three of these measures. The problem that quickly developed from that implementation was premature failures of transaxles, especially those that were under slight heavier duty than normal, Camry transaxle in an RX300... So the 2004 and later models use a DBW throttle system to delay the onset of engine torque to "protect the drive train". As you coastdown to a full and final stop for a traffic light or sign the transmission will automatically shift into neutral and into low gear as you come to a full stop. No problem. But if in the middle of that coastdown, and after the system has shifted into neutral, you reapply pressure to the gas pedal the transmission must be quickly shifted into 1st gear. If you own an RX300 the engine torque will begin to climb before the "downshift" transaxle clutches can fully and firmly seat. If, on the other hand, you have an RX330 them the DBW system will be used to delay the onset of engine torque long enough for the clutches to seat. Same goes for downshifting, sudden returns to acceleration, at highway speeds. Note that the use of premium fuels are a modified IAT to artificially enrich the mixture would result in a lower engine lugging range, RPM, which would result in alleviation of some instances of downshifting (the engine still has "pull" at the higher gear already in use) and therefore fewer occurrances of hesitation or delay.

Well, yes, on my way back home from the 24 hours of daytona and didn't take the laptop. Each time you apply the brake the Trac ECU checks the accummulator pressure level and if it is low it restarts the pump. Absent actual useage the pressure should never leak down except for maybe long periods in the garage. If the pump must be restarted ten time sequentially then you have a pressure leak within the system and the diagnostic comes on. It might be a good idea to have the brake system flushed and refilled and be sure the bleed valves on the accummulator pump and ABS pump are bled/opened. That was what cured my Trac problem.

YES!

Most likely the front wheels started to slip very slightly which caused the system to bring the rear drive online, if it wasn't already. If the front still slipped, as is very highly likely, then TRAC would begin "moderately" (PULSING, herky/jerky) braking the front to help alleviate the front wheelspin while at the same time dethrottling the engine/motor. At that point you're STUCK! In a standard RX you could pull the ABS pumpmotor fuse to disable TRAC and GO ahead.

That was right after I purchased the RX, new, and if asking the VC to stiffen up and do its job for all of 30 seconds results in it failing then it is really a poor design. But you make a really good point, maybe the VC didn't survive the work level it encountered during the two snow and ice storms it has had to endure in 50,000 miles.

The center diff'l control coupling (viscous "clutch") is mounted entirely within the "transfer"/PTO case and can be replaced without opening the transaxle case itself. The purpose of the VC is to provide a variable level of locking between the two center diff'l output drives if/when those two drives do not have equal rotational rates, the front drive wheels (90% torque biasing) are slipping in relation to the rear wheels. The VC is connected between/across the two drive outputs of the otherwise fully OPEN center diff'l. If those two output drivelines have a different rotational rate then the viscous fluid between the two very closely spaced VC clutch plate sets is "stirred" violently and the resultant turbulence heats the fluid. Were it not hermetically sealed within the VC casing it would expand dramatically due to specific formulation of the fluid. Since it cannot expand the EFFECTIVE fluid pressure rises, "thickening" the fluid, and thereby increasing the coupling coefficient between the closely spaced VC clutch plates. Basically the VC will remain "flaccid", no significant locking of the two center diff'l outputs, unless those outputs have differing rotation rates. The longer and/or greater the rotation rate differs the higher the temperature of the fluid will rise and that results in stiffening the coupling across the center diffential. Some VC designs will have a small bubble of air/gas injected during manufacturing to delay the onset of VC coupling. The gas itself must be fully compressed before the fluid begins to thicken enough to provide any significant level of locking. Other systems provide quicker VC coupling by having different final drive ratiosn front to rear such that the fluid is always heated up to some inital level of coupling. It appears that Lexus uses this latter method since the front and rear final drive ratios are different on the RX300. Testing is relatively simple. With all four wheels off the ground and the parking brake applied the engine should drive the front wheels easily at a fairly low speed. The center diff'l is open and there should be no loading of the engine via the rear parking brakes until the VC begins to stiffen. On a 4 wheel dyno my 2001 AWD RX300 at 40MPH simulated road speed there was no measureable engine torque at the rear wheels initially. It took almost 30 seconds at 40MPH simulated roadspeed before the rear wheels got up to ~25% of the engine torque delivered.

First, I would recommend the next time drop the pan and clean the "debris" out. I had about 1/8 inch of clutch wear material in the bottom of the pan at ~40,000 miles. My 2001 RX300 is AWD and I have become somewhat suspicious of the fact that the transfer/PTO case has lots of exterior cooling fins. Additionally I have come to believe that the VC, viscous clutch/coupling within the PTO is, has, been the source of an inordinant level of heat generation and has now failed, seemingly, in the (mostly) locked position. That could put a lot of stress on the driveline resulting in further overheaing problems. It goes into the shop to check that next month, the first time since 93 that I have had any Lexus in the shop for ANY reason.

Your O/D lockup clutch has/is failing. Dual failures, simultaneously, shift solenoid and speed sensor, are highly unlikely. Speed sensor is used in all modes, gear ratios. Disconnect/reconnect the battery to reset memory, lock out the O/D and drive the car for awhile. If you get a "repeat" shift solenoid and/or speed sensor then continue looking there, otherwise...... Lockup clutches are not very sturdy, high miles in hilly/mountainous terrain, consistently heavy loading, towing, etc, lead to early failures.

You will NOT believe this! Googled for "Atkinson cycle" & "intake noise". I was curious if the intake noise from the Atkinson cycle's reverse airflow, combustion chamber back into the intake manifold, in a 3.3L V6 might be at least part of the reason the RX400h doesn't make use of this fuel economy method. Inadvertently found: July, 8th, 1999 Final report by SRI, Sierra Research Inc, on "Alternative and Future Technologies for Reducing Greenhouse Gas Emissions from Road Vehicles" One of the conclusions is that if the industry switched to 5-speed automatic transmissions, made use of ASL, Aggressive Shift Logic (quicker upshifts), early torque converter clutch lockup, and shift into neutral with brake application and engine at idle, a 9.8% improvement in fuel economy would result. Industry response was that "driveability" would suffer. Welcome to 2006.

IMMHO the greatest problem with Lexus dealer service is the product itself. Extremely reliable. Dealer service bays would be empty if they could not sell you services your vehicle doesn't need. Lexus needs to allow combined Toyota/Lexus dealerships so the service aspects will have a more reasonable "base" to draw from.

I don't like the Lexus climate control design so I modified it to work to my satisfaction. I didn't like the idea of only using snow chains on the front so I added wheel spacers so I could use tire chains on the rear primarily and add them to the front if it became necessary. If my transaxle should fail prior to my next SUV purchase (most likely to be an RX400h) then it will be DIY time. That way I can find out just exactly what is failing and at the same time modify the center diff'l so the mechainical drive is only to the rear and the VC provides drive to the front. Life is a compromise and so is buying the most appropriate SUV for the purposes you intend.

Only two corrections to the above. If you use the defrost/defog/demist mode the blower will run before the engine water jacket is up to temperature, 130F. The A/C compressor will shut down anytime the OAT is consistently near or below freezing.

Typically, the RX300 is rated for 3500lbs with the factory tow system. I've pulled my boat for short distances but do have the factory tow. I would believe it all depends on what boat you are pulling. I wouldn't question it if it were a light boat 2000lbs or less. My boat weighs 3000lbs without the trailer. Compared to the MB SUV, there is no match to Lexus reliability and quality. Although I think the MB doesn't lack quality but if you compare the repair needs, there is no comparison. Good luck! I wouldn't advise anyone to buy an RX300 or 330, especially for towing, due to the instances of premature transaxle failures being reported. My own 2001 AWD RX300 came from the factory with the towing package (removed the hitch immediately), external ATF cooling radiator in front of the right front wheel well. and NO requirements for transaxle maintainance for the life of the vehicle. At 40,000 miles the ATF was looking murky and smelled burned. Dealer advised that I needed to flush and refill every 15,000 miles, OF COURSE! Contacted Lexus about the matter who referred me back to the dealer. Now at 50,000 miles I fully expect a failure before 75,000 to 80,000 miles even if I keep the ATF in good "working" order by removing the clutch wear debris via drain and fill every 15,000 miles.

" I've done what you stated..." Who?

By all means do not give up that XC90, certainly not for ANY RX. Should you have need of it your XC90 has one of the best AWD and stability systems on the market today. And it may be that your dealer was correct. IF you did not "retrain" or normalize your window full up position after your installed the aftermarket devices then it is likely that you are responsible for the failure.

Temporary fix: Turn it to max heat, turn the A/C off, use fresh airflow mode, footwell airlfow mode, and then use the blower speed to regulate your comfort level. Max heat position over-rides all sensors and just configures the system for max reheat of the incoming airflow.

First, the following information is being taken from the Lexus Repair Manual, titled: U140F AUTOMATIC TRANSAXLE Jan., 1998 Pub. No. RM632U For clarification, within these manuals of various years Toyota often uses the terms "transfer" as in transfer case/components, interchangeably with PTO, Power Take-Off. Prior to 2004 the PTO contained a viscous clutch/coupling, and as of 2004 this component is simply left out. Things can be a bit confusing in trying to analize just what drives what as both the center and front differentials are contained with a single "casing". The best pictorial is on page AX-1 but I had to blow it up by a factor of 4 to really see how things were coupled. Bolted to the center diff'l case/carrier is a ring gear which mates with the final drive output gear of the transaxle. So the transaxle output drives the center diff'l directly. One output side of the center diff'l drives the case/carrier of the front diff'l and the other output side drives PTO/transfer case ring gear which in turn drives the rear drive shaft via a pinion gear. Prior to 2004 there were three drive couplings from the transaxle case into the PTO. First, a solid inner shaft to couple one side of the front diff'l to the US passenger side front drive half-shaft. A hollow drive shaft immediately surrounding the inner solid shaft to couple the front drive line to one side of the VC. And then yet another hollow shaft outside the first one to drive the other side of the VC and the rear drive shaft via the ring/pinion arrangement in the PTO. As of 2004 the VC and the "Middle" hollow drive line were dropped. Although the VC was mounted, fully contained within the PTO case, it was effectively mounted between the front drive line and the rear drive line so when it activated, stiffened, the effect was to partially "lock" the otherwise fully "open" center diff'l.

No, the transaxle output drives the center diff'l directly. The center diff'l then drives the front diff'l and the PTO. The PTO is driven via a hollow shaft surrounding the right front half shaft. At least that's the "case" according to the Lexus shop manuals for the 2000, 2001, and 2004 Rx AWD systems. Don't have the manuals for others. I use the ECT switch a couple of times. After each use I could smell hot trany fluid. I stopped using it. If you use ECT and accelerate aggressively you're asking more of the transaxle's 2nd gear clutches than they can provide without slipping and overheating.

Yes, it's only the PTO/transfer case that uses gear oil. I don't think you can "refill" the center/front diff'l except via the ATF fill tube.

It is a lot more likely you were smelling the brake pads being overheated due to Trac activity. Since the VC mostly remains flaccid almost all of the engine torque remains at the front resulting in continuous slipping of the front wheels versus the rear on a slippery roadbed. Also remember that Trac braking is used to simulate a real, mechanical, LSD at both the front and the rear, not that it ever really has need to do that at the rear. The only way the system can overcome front wheelslip/spin and allow you some simplance of directional control is via the Trac system's use of PWM, Pulse Width Moduation, of the front brakes. I'm surprised you didn't also encounter engine dethrottling along with the Trac system activation.

If it takes "over the top dramatic" to get a few FWD owners to be just a bit more cautious when driving in wintertime conditions and that results in the saving of just one life then I can live with that.

A True Story.... Several years ago TeamSeattle(.com) ran two Saleen SR-7s at the 24 Hours of Daytona. Prior to the race one of the cars had been over-heating and had to be torn down to replace both radiators. Just before race time, really too close for comfort, the car was finally re-assembled and when the engine was started it immediately went WOT and luckily was shut down before anything was damaged. For some reason the engine control ECU had "forgotten" the parameters for the DBW gas pedal/throttle control system. Picture this.... A technician laying upside down, butt on the drivers seat, head and shoulders in the brake/clutch/gas pedal "tunnel". At the same time the Saleen factory engineer, white shirt and tie, is standing behind the cab with one foot on each exhaust manifold of the big-iron Ford V8, laptop computer laying on the cab top in front of him. The Saleen engineer has the technician alternate the gas pedal position between "neutral" and WOT while he manually moves the throttle itself to the same, appropriate positions, meantime using the laptop to "tell" the Saleen's engine ECU to "trap" the sensor signals to save the positional parameters to coordinate the throttle valve position with the gas pedal. Often wished I had made a video of the procedure. So, how does your car "learn" these DBW parameters, for learn it must. And does it continuously re-adjust those parameters from time to time if it decides the previous parameters are for some reason no longer valid? Floor mat laying lightly on the gas pedal for instance. Or someone left foot braking??? I can imagine a VERY confused engine/transaxle control ECU should the gas pedal suddenly go "negative" from the previously memorized neutral position established while that floor mat was in place and now removed or someone's right foot being finally removed from the gas pedal after "resting" there even with the brakes applied. I have no doubt that the previous "false" neutral gas pedal sensor parameter would be immediately scrubbed, erased, but how long would it take, and HOW would it, go about re-establish a "certain", for sure, neutral position parameter? And just how would the transaxle "act" until a new gas pedal neutral position parameter is memorized?

Be aware that it is not at all unusual for the catalyst to come apart in chunks and then partially or almost fully block the exhaust flow. Other than poor engine performance the usual indication is a bright red, HOT, exhaust stack upstream of the converter after a relatively long drive. Do not remove the catalyst heat shield if you often or sometime park over dry grass or "like" flamable material.