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Lexus RX AWD vs FWD Questions



  • Hello Jack,

    I have bought a RX350 2010 last week and on my first mountain road trip I had the same experience with the message on my display showing Power Steering problem.
    The problem is my power steering stopped working and I have to stop the car and turn the engine off and on to get back my power steering working. It happened 3 times and in all cases my speed was very slow. However it could be a disaster if it stops working at high speed mountain roads. I checked the user manual and it says it is because of EPS malfunction. Have you been able to solve your problem?
    Dose any one has a clue on this failure. I would appreciate your comment.

  • wwestwwest Posts: 10,706
    These new EPS, Electric Power Stearing, systems are quite seriously UNDERPOWERED insofar as continuous, constant duty, (lots of stearing corrective inputs in a relatively short period) is concerned. In that situation the electronics control module's power transistors will often overheat.

    But I have understood that the above is explained in the owners manual.
  • jacks2jacks2 Posts: 45

    Unfortunately the service department was unable to reproduce the problem during a "lengthy and comprehensive test drive". Ironically my odometer logged only 1 mile which says a lot for their lengthy test drive or credibility.

    So far I find my Lexus post purchase experience disappointing. What is the time element for one to receive a factory survey?
  • Hi Jack,
    I live in Iran and I don't think that the factory will send me a survey at all. These cars are designed for Middle East Arabic countries like UAE and Saudi Arabia and are imported to Iran by individuals. However, I send the car to the local dealer of Toyota and they could not diagnose the problem so far.
    As far as I think you have better access to services and supports over there, I really appreciate if you keep me posted on any progress to solve this problem.
  • dear Willard,
    Thank you for your comment on my post. You have mentioned, EPS is powered for use at low speeds. Dose that mean, this problem will not occur at high speeds?
    To be honest, I don't dare to drive my lexus anymore.
  • wwestwwest Posts: 10,706
    Think about how much use the EPS would be put to if you parallel parked on a gravel roadbed 10 times in short succession.

    As may already know less power stearing effort is required the higher you speed is.

    I wouldn't go so far as to advise you not to drive your Lexus, just be fully aware of the EPS limitations. And in the past I thought the EPS would first drop into a low assistance mode when it began to overheat with a warning to the driver and then only shut down completely if the warning wasn't "heeded".
  • Thank you for the information. Now I have a better understanding of EPS system. However, most of the time I received this message I was driving at a law speed between 20-30 km/hr at a normal driving condition without any harsh use of EPS.
    And I lost my steering power almost at the same time I received the warning message.
  • wwestwwest Posts: 10,706
    Roadbed ruts, frozen snow/slush...??
  • yeah, there were roadbed ruts first time it happened to me. However, It is getting worse, I receive this message two to three times in a short drive from my office to home. There are some speed bumps on my way home. could that be the reason??
  • wwestwwest Posts: 10,706
    Either your EPS is defective or for some reason it is having to work harder on a regular, consistent, basis than the designers expected. Road rutting would undoubtedly be a contributing factor that first time.

    Upgraded to wider tire tread with more CSA, stearing force shock absorber added, lack of adequate cooling for the control module..??

    Maybe even a failing CV joint.

    I have even heard of the torque tube, stearing force sensor, being twisted, taking a permanent twist, due to extraordinary driver stearing input forces being used at some time in the past. The effect from this latter often results in the EPS partially fighting the driver's stearing wheel input, even to the point of opposite forces to the input.
  • jdw48jdw48 Posts: 4
    I have a 07 350 I just purchased, and have a rattling noise in the left side sunroof area, do you know what they did to fix it. it's out of warranty (miles)
  • I got the same problem on my RX350, rattling noise on coming from the left side of the sunroof. Anybody ????? its driving me nuts.
  • Has anyone figured out how to fix this Rattle problem, i have taken this car apart trying to find it. HELP
  • jacks2jacks2 Posts: 45
    edited December 2010
    Drove 40+ miles through heavy snow this week keeping speed at or below 20 mph without any noticeable slippage or loss of control.

    Initially ETC Snow control and AWD lock mode failed to engage nonetheless I was able to drive through an un-plowed area in bumper high snow without the benefit of those features.

    I felt my 2010 AWD RX ( 19" Bridgestone MS tires) handled as well or better than my 2007 AWD RX did.

    A visible AWD medallion would be helpful when passing a chain control checkpoint.

  • wwestwwest Posts: 10,706
    Your post reads as if you have the earlier RX350 F/awd system WITHOUT the ability to manually "lock" the rear drive in at low speeds.

    In any case I would NEVER drive any F/awd system, and most certainly NOT the early RX350 version, without at least the rear tire chains when the "chains required" sign is up.

    But then it's your life at risk, not "mine", mostly.
  • wwestwwest Posts: 10,706
    "..ETC Snow control and AWD lock mode failed to engage.."

    What were your indications of this, how did you know...?

    To my knowledge ETC only modifies the shift pattern and the DBW gas pedal response rate/"gain". I also understand that the manual F/AWD lock mode only works at lower speeds, below 20(?) mph.
  • wwestwwest Posts: 10,706
    Has it occurred to you, or any RX owner for that matter, that Lexus does not label the RX as "AWD" since there might be some serious liability in FALSELY making that claim..??

    The RX series has not been even a "true" F/awd system since the beginning of the '01 model year. The revision in 2010 represents a VAST improvement but still NO CIGAR.

    No RX should be trusted to perform dynamically, on an adverse condition roadbed, as would an actual F/awd or even a R/awd system, let alone a TRULY capable RWD/4WD vehicle.
  • jacks2jacks2 Posts: 45
    When first starting and attempting to engage ETC and lock mode no indication appeared on the instrument panel. After several minutes of driving control switches worked and displayed on the panel.

    "Lock mode" did cut off above 20 mph, my 2007 AWD did not have a lock mode.

    Do you have an RX or have you personally operated one under adverse driving conditions?

    This is my second RX, other than crappy paint that chips much too easily I like this vehicle.

    Thanks for responding to my post, have a happy new year.

  • jacks2jacks2 Posts: 45

    "I would NEVER drive any F/awd system, and most certainly NOT the early RX350 version, without at least the rear tire chains when the "chains required" sign is up. "

    Why the rear? The manual recommends chains on the front wheels.
  • wwestwwest Posts: 10,706
    "lock mode" is only available with the newer F/awd system, the one that has an electromechanical clutch housed in the front of the rear diff'l. The lock mode indicator may not go off but the actual rear drive engagement goes off at higher speeds.

    My first RX purchase was a 2000 and then the next year I traded "up" (or so I thought at the time) to get the TC, VSC, and HID headlight options. The '00 had a more functional F/awd system but as it happened that was at least partially the reason for all the premature transaxle failures for the 99-00 RX300.

    So as of 2001 the rear LSD option was dropped and the VC fluid formulation was changed to forever remain "flaccid". The VC was really of no matter anyway since TC activation will never allow it to come into "play". That basically why the VC was dropped entirely during teh RX330 model run. The RX300, 330 and early 350's or basically ONE-WHEEL drive vehicles, 3 simple "open" diff'ls, front, center, and rear. TC, Traction Control, is used to "simulate" F/awd functionality but only reactively, AFTER wheelspin/slip is detected.

    My '01 F/awd RX300, now at ~80,000 miles (2 ATF drain/refills) has survived no less than 10 winters, wintertime trips to MT, Ski trips, etc. We have about 3 inches of hard frozen, crusty, snow and ice on the ground here at this very moment.
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