2005_RX330

For the record, in the 2004-2005 RX330 Lexus TSB TC005-03 Revised, Title ECM Calibration: Shift Feeling Enhancement, they mention certain "calibrations" (what I call "firmware"). The date shown on every page of the TSB is August 11, 2003 (sic), which must be a mistake because it precedes the affected vehicles; presumably it's a typo. Now, the revision history contained within the TSB is detailed as two revision notices, the first notice dated May 20, 2005 and the later notice dated Feb 9, 2006. In that TSB they reference the "calibration" (firmware) by number, which supersedes prior releases and provides the "fix" which is the subject of the TSB ("shift feeling" in this case). For my RX330, the two relevant calibrations listed in the TSB are 34874100 and 54828100. Make mental note of these. I connected my 2005 RX330 to Techstream and checked the installed calibrations (firmware); see the attached images. It's calibrations are exactly those mentioned in the TSB. So my RX330 has more recent firmware, presumably relevant to 2006 and even sometime later, but not necessarily the most recent; that's still TBD. With regard to the fans' operation (the topic of this thread), the question still remains whether there was a even later calibration (firmware) than that provided by this TSB that changed / improved their operation, i.e., enabled them to run on HIGH during certain times when the AC is operational. I'll write more as I learn more.

When the RX330 engine gets hot (>207F) the temperature switch (atop the engine near where the upper radiator hose attaches; a grey, two-wire connector affixes to the temperature switch) opens (i.e., goes open circuit) which in turn causes the ECU to activate both radiator fans (that is, if they aren't already running on account of the AC being engaged). It's an easy matter to test the circuit that supports this function, as follows. If the connector is removed from the temperature switch (this is an easy task and can be done with engine on or off) and the engine is running (doesn't matter if the engine's hot or cold) and the AC is off, the fans should run at their maximum speed. If not, then some repairs are in order. Note: Removing this connector to test in this way may set an error code and trigger a warning light on the gauge cluster, but after reconnection be patient; the warning will clear after a few stop/start cycles. Your comment that "the car only ran hot when stopped at a light" makes me wonder if something might be amiss with the fans. You're in Kansas. I'm in IL. I've never seen the temp gauge go any higher on our 2005 RX330 than "in the middle", normal operating temp. If you're seeing high(er) engine temps, check the operation of the fans. You may find you have some other problem causing your condition, but checking the fans is an easy and relevant first step.

I've updated the matrix which I originally posted (above) to add clarity and reflect certain other cases. See below (sorry for the small image, it was constrained by width):

RX400h: Exactly... which is why I wonder if this behavior is peculiar to an ECU firmware release / model year and factory service manual release, and bears some dependency on the state of charge. Read on... The fact the ECU doesn't command the cooling fans to HIGH, ever, when the AC is engaged, seems like a major oversight on Toyota's part. Yet, this is how the behavior is described in the manual (the manual's quite terse actually, if you've ever seen a Toyota manual; they're not very good as compared to factory manuals for GM or Honda) and jibes with my observations to date. Now, I should add that if the AC system is in an overcharged condition, the "outage" due to high-side pressure > 460psi will occur under less demanding cooling conditions than otherwise. That's actually how I discovered this behavior, back in 2019, when I serviced my own system and charged it with the maximum (according to the factory manual) 23oz of R-134a (this was during replacement of the condenser). The "outage" as I've described in my previous post occurred quite regularly, and I mitigated the problem by bleeding off ~3oz of R-134a so as to put the system on the low end of the factory charge spec (19.4oz; see pg. AC-129 RX330 FSM). Notably, as these systems age (and leak refrigerant) the problem becomes, I suspect, less likely to occur. I should confer with the local Lexus dealer regarding the firmware release(s). I have very rarely taken my RX330 to the dealer as I handle most service procedures myself (excepting recalls of course, e.g., for the leaking master cylinder). Other owners, who may have had their similar model RX330 in the dealer more regularly, may have had a (complimentary) firmware upgrade at some point in the past or received a firmware upgrade on account of an AC complaint. I can't help but wonder too, if (when?) presented with these symptoms, the dealers simply bled-off some refrigerant to mitigate the problem.

With reference to my post just prior (above), a problem arises when the vehicle is stationary, the ambient temp & humidity is high enough to cause the AC high-side pressure to exceed ~460psi, yet the engine temp remains <207F for a period of time. In the above situation, what happens is: - The ECU stops cycling the compressor because the high-side pressure exceeds ~460psi. ALSO, the fans, which were running at LOW (see the matrix in my prior post), get switched OFF (which is an unfortunate Toyota oversight). - The high-side pressure falls very slowly because there's no airflow on account of the fans being off and the vehicle stationary (I've shown this to myself on my own RX330, using pressure gauges on the high-side). - Until enough time passes that the high-side pressure drops to ~370psi, the AC system is effectively suffering an OUTAGE and the cabin comfort degrades accordingly. - Once the high-side pressure finally drops below ~370psi, the ECU will begin cycling the compressor and turn the fans on (LOW). - IF, during the above OUTAGE, the engine temp increases >207F, the ECU will turn the fans on HIGH (see the matrix in my prior post). This fortuitously benefits the AC by causing airflow across the condenser and lowering the high-side pressure rapidly; once the pressure drop below ~370psi, the the ECU will turn the fans on LOW (not HIGH, oddly, in spite of the engine temperature) and engage the compressor clutch; subsequently, I believe (but have not shown definitively), the ECU will turn the fans on HIGH if the clutch is disengaged during cycling activity while the engine temp > 207F (i.e., AC selected ON at the dash but ECU is commanding the compressor clutch off on account of adequate evaporator temperature). Clearly, other scenarios which cause airflow across the condenser (vehicle motion, air currents / breezes) have the same effect as that described above. Mull this over. I've tried to describe the behaviors accurately but the description I've provided might be lacking. I must add that this behavior, which I've observed and which jibes with the service manual, may be an artifact of the firmware release present in the ECU. Toyota may have, at a later time, released an update to the firmware (and the service manual) which improves upon this operational scenario. I have not investigated this possibility.

I know this thread is old, but I've noticed similar behaviors on my 2005 RX330. First, to carlover_rx, in your original post, where did you get that matrix for "CONDENSER FAN - ON-VEHICLE INSPECTION"? I have the RX330 factory service manual (Lexus') and I have not found that matrix in the manual. However, from what I have found in the manual, the operation you describe for your RX330 jibes with what I've observed on my RX330, and jibes with the operation specified in the manual. But, it doesn't jibe with the matrix you posted. What's notable is that - the cooling fans run on LOW whenever the ECU engages the compressor clutch. LOW... ONLY, it appears, when the clutch is engaged, never HIGH. - the cooling fans run on HIGH whenever the engine coolant temp > 207F AND the ECU has the compressor disengaged for any reason (i.e., AC off or AC high-pressure > ~460psi; see my matrix below). - if the AC is selected "On" (i.e., switch on the dash) the ECU will cycle the compressor unless the high-side pressure side exceeds ~460PSI; if that happens (e.g., sitting still in a parking lot on a hot day), the ECU stops engaging the compressor until the high-side pressure drops to ~370psi. I'll summarize this with a matrix and will comment more in a follow-up posting. The resulting operation of the AC is non-ideal, as you and I have seen. Reference RX330 service manual "AIR CONDITIONING" pgs. AC-53 - AC-55, and COOLING pgs. CO-2 - CO-6.

I've seen a similar behavior on a '94 Cad. The engine wasn't cooling right (the thermo was bad, it turned out) and when the engine temp exceeded a threshold the AC would stop working. I assumed, but did not determine, that the ECU simply shut down the AC in order to aid in engine cooling (e.g., to prevent the AC condenser from pre-heating the airflow through the radiator). Fixing the engine cooling problem "fixed" the AC "problem".

You mentioned that the flexible exhaust coupling has been replaced with a solid one (if I read the posting correctly). A solid pipe will cause the entire exhaust system to vibrate with the engine and, in certain circumstances, make the vibration more evident to the driver. By way of example, I once owned a 1996 Honda Accord which had an (OEM) solid intermediate pipe in the exhaust system, i.e., no flexible coupling. Honda later wrestled with owner complaints of noise and vibration in that model but never instituted a proper fix; I eventually had that pipe replaced with a flexible coupling which improved (reduced) the amount of driver-perceived vibration greatly. It's worth noting that Honda's re-design of the Accord in 1998 incorporated a flex pipe in the exhaust instead of the solid pipe, eliminated the problem which was designed-in to the 1996-era models. If you had an engine miss it might contribute to your problem, but it would also trigger a error in the ECU and illuminate the appropriate (Service Engine Soon?) light. An injector issue could contribute to engine roughness, particularly near idle, but might not necessarily cause the ECU to generate an error.