GSLV6

I'm pretty convinced (in my case) it was 100% related to the auxiliary battery. Despite Lexus saying that they checked the PBD module and that "it had failed" and was "most definitely dead" quite obviously it didn't and it wasn't. The current draw is quite high for the tailgate motor and it draws a fair amount for a fair time so if the aux battery isn't healthy enough, part of that circuit will have a voltage drop sensor so rather than damage anything, it will cut out, which is what happened in my case. Recovering the battery demonstrated that but given that Vadim changed his battery then it does appear that some of the SM components have failed I had something similar happen on an old electronic fuel injection module which had entrapped moisture causing issues and used to heat it with a hair dryer to get my bike started! Whilst I work with electronics, it's in the audio world but there are some common failure symptoms and mechanisms. 'Lytic caps can increase in ESR and drift with age and heat and throw circuits out of kilter but the likely cause with these SM boards is usually in hyper sensitive components like SM fets and the like. They only need to be knocked and they fail. Unfortunately, such miniaturisation necessarily means that when such things happen, discrete repairs become largely impossible and the whole board needs swapping out, usually at ££££'s for pennies worth of components.

Fantastic Steve, thanks. Did you disconnect the old one without using the jump lead trick to keep your car settings first or just swap it over?

Just the information I needed. Even if it lasts two years it'll match what I've had from the OEM one. A belated thankyou for posting the details.

I seem to remember Lexus service saying that the warranty only covers it for 2 years Herbie. That being the case it's either find an aftermarket replacement for half the price or stump up £220 for a Panasonic.

unfortunately not...at least I think not as it's two years old.

Thought I'd update this thread since self diagnosing the issue and finding Lexus service team were wrong to quote me for a new Power module and ECU for the rear door. For anyone suffering similar issues, the culprit all along is likely to be the auxiliary battery. Unless its charged on recover mode at 4 amps or less, it'll not properly recover, and permanent damage is likely of it dips to under 50% capacity/charge. Trouble is, most battery chargers just tell you it's charged so you have to buy a battery checker (mine coast me £30) which tells you the charge capacity as well. No expensive parts replacement needed. It transpires that the battery needed a full week on trickle using the agm mode on my CTEK. Lexus supposedly checked it but obviously not the current charge capacity! Once recovered, the tailgate and rear power module worked absolutely fine....oh, up until today when I went to start the car and got nothing as the battery finally died on me (which I was expecting). Anyone know of a drop in agm replacement 220long x 180 wide x 180 to 200 tall? I can't find one for love nor money!

Hi Guys did anyone ever get round to posting the details of a replacement aftermarket leisure battery for the RX3 450h? My second one in 5 years has just died (original spec panasonic). Almost fried my CTEK charger trying to recover it to no avail. I'm having a hard time sourcing a replacement due to one problem.....size! The original has no wriggle room in the battery7 holder and measures 220 long by 180 wide by 200 tall (mm). I cannot for the life of me find a replacement to those dimensions, although there are plenty of higher spec batteries than OEM at half the cost. I'd be very grateful if any of you has a make and model that would fit. Thanks Paul

Yes, however the OP specifically called for comparisons of performance, power and emissions, hence that's all that I commented on and there was no mention in the OP of restricting responses to the 4RX. The 3RX don't forget, was still being sold on forecourts new and unregistered, and the major changes to information supplied from Lexus were indeed between that of the outgoing 3X and the incoming 4RX. Have there been any significant changes to the IV engine and drive train Colin? I didn't think there had been. It's much the same now as it was in 2017...at least to drive (I was also satisfied that there was so little difference between my 3RX and the latest 4RX in performance after driving a newer one that I decided to wait until they came out with something lighter which will require more efficient motors and batteries). Great car...just wish it was 500Kg lighter! The niggles on handling, bushings wear and economy are much to do with it being overweight. "Reassuringly heavy" some might say! 😆

That's true Colin but they did change the advertised specs from the 2016 3RX which was the point I was making above.

The engine was updated for the RX4 late 2016/early 2017 which gave it a few extra ponies going from 297BHP to 305BHP or thereabouts. The newer version is also slightly larger and as it uses the same hybrid train as the older one, one assumes that with slight engine tweaks and the larger size it may also have been a little heavier than the outgoing 2016 RX3 model which had a max kerb weight of 2200Kg in Premium trim. It was 2017 that Lexus amended their fuel consumption figures, not that they were really much different to the outgoing model which claimed way optimistic fuel economy. Lexus released figures which amended earlier 54mpg claims back to 44mpg which some, with a following wind on the flat, claimed they could just about achieve although real world for mixed driving remains low to mid 30's. The higher CO2 would be a cost at a guess of the larger vehicle but with revised RX4 models claiming improvements over the outgoing RX3 in this area, not a lot of that makes sense. There is little real world performance difference between RX3 and RX4 models. Tests were conducted using the RX3 F-sport which was measured at 6.8 seconds 0-60mph and a standing 1/4 mile of 15.1 seconds. Lexus claimed I think closer to 8.5 seconds. The RX4 is claimed to be 7.7 seconds and was tested at about 7 seconds. Take all of this with a pinch of salt as the output such tests are HIGHLY dependant upon the fuel used and the altitude at which these tests were conducted so they could vary by a second and a half either way depending on where in the world you are and on the octane rating of the fuel used. Suffice to say for a large barge using a modest 247-250 BHP V6 with electric motor assistance, they are sprightly enough although due to the combined torque figures (note, these have never been released to my knowledge....quoted torque I think is for the gas engine only, although I may be mistaken on this) not in the same league as some of the competition as that is not what they are all about. Refinement and comfort over longer journeys is their forte, not high performance.

I'll have to check my battery. I set my CTEK to "recover" mode and it doesn't differentiate by having a separet one for AGM in recover mode....just one recover to desulpate a flattened battery of any sort and trickle charge in steps with varying current pulses and voltages. I normally leave it on "car" (or LA) as my oversight is I cannot remember if my current replacement is an AGM. If it was, I may have shortened it's remaining life by not using the AGM charge option. If not, it should be ok. Either way, thank you Rob for some most informative and instructional posts. I'm a chartered engineer too but in my case a civil engineer. (I have though retrained in electronics as I now run my own hifi/loudspeaker company).

Where I live, there's steep hills in all directions so from cold, doing the school run = 16mpg there (3 miles of uphill with one section at an average 12% for 1.5 miles), but I get 50mpg on the way back! It's only a short trip so not really representative. On average, each tank gets me between 27 and 29mpg. On longer motorway runs it's more like 32 to 33mpg (indicated 75mph...I checked my speedo against GPS at an indicated 77pmh is a true 70mph). Oddly, travelling at higher speeds (not excessively so) makes little to no difference. The real economy is between 55 and 65mpg where I get 36mpg on the flat on a longer run if I'm really gentle with the gas pedal. By way of comparison, a friend's BMW X3 diesel (3 litre) manages 28 to 30mpg locally and up to 37mpg on a motorway run. Not a lot in it and his only weighs about 1900 Kg so we can't expect more than high 20's on local run-abouts or low to mid 30's M-way. Lexus figures are hopelessly optimistic, but so are those of all other manufacturers because they test them without wind resistance on a rolling road at a steady 56mph which is just not representative of true load and drag.

The regeneration though I thought had nothing to do with the battery. It is not directly hooked up. The effect on any battery is the same...they can only be charged via the inverter and charging circuit or direct from the hybrid battery via a charging circuit II'm not sure which in this cas e to be honest but it has to be one of those) which steps down and regulates the voltage. Any differences will be purely down to the charging efficiency of the battery type under deep cycle load conditions. There is no good argument for insisting that the OEM battery will be the best...that's a misleading statement and simply is not true as many alternatives will meet or exceed those specifications. ANY battery that meets the specifications required ie deep cycle of sufficient AH will be more than adequate and I've already proved the life of the wet battery I replaced my panasonic with has been longer. The incidences of anyone being injured by a lead acid battery in the cabin I suspect are probably so low as to be statistically irrelevant, and whilst the outcome could be locally serious but still relatively minor, the risk is so low as to be negligible. There are many other outcomes of serious accidents that are likely to cause far greater injuries or risks to long term health. I speak as someone involved in a very serious accident whilst a passenger. You accuse Rob of Hyperbole Barry but you have to admit that your viewpoint has little factual basis to support it and the risks you mention are much exaggerated. Just saying. no offence intended.

Hi Great car and still one of the best cars I ever owned. The things to be aware of, if not already done, at this mileage are shocks do fail on these sometimes rather too prematurely. They were under specified by Lexus who for reasons known only to themselves refused to ever properly address the issue. They are not cheap top replace and if one is weeping, then it's time to replace not just it, but both as a working pair. It transforms the handling when you have these renewed. The other bugbear is the exhaust at the point it splits from one to two at the Y junction. This is a point of stress and the welds tend to fail here eventually. Mine went at 67K miles and cost £750 from Lexus for a new back box and Y junction (no aftermarket parts were available). Finally, the TPMS on mine was very temperamental, and eventually the transponders in the wheels failed, setting me back £284 to replace. I took the opportunity to powder coat the wheels as all Lexus cars of this period had awful laquer quality, not up to British winter driving. The salt destroys the allows once the lacquer starts to bubble. Other than these issues, mechanically the cars are solid and that engine is an absolute peach. Much more economical than the 4.3 V8 and really not a huge amount slower.

My current battery is a conventional deep cycle wet battery Rob. I saw little advantage in paying the extra for an AGM and equally little disadvantage to my current wet battery.

My long term average is 27pmg based on the trip computer, and I don't have a lead right foot. No doubt it would be better than that in a flatter area. On several 200 mile trips, mostly M-ways at 70-75mph it returned 32mpg. Cross country it delivers closer to 34-35mpg in light traffic with infrequent stops. Such a heavy vehicle will be very sensitive to how gently or not the right foot is used. The old Rav4 gets closer to 36mpg average and on longer runs, closer to 42mpg but it is a whopping whole tonne lighter! Sorry to the OP for the extended thread drift.

Hi John yes, it was an official warranted Lexus vehicle bought at Lexus in Cheltenham. They have been excellent throughout and most work was in fact covered under warranty (I took the extended warranty out). I have nothing but praise for their customer service but they're really as disappointed and surprised as I am with these series of events, and have no answer for the failures other than bad luck, which I am prepared to accept. The more complex these cars get, the more I guess we ought to expect problems, especially at the 5 years plus age when many sensors and electronic devices have reached their designed and specified reliability age. I, for one, don't need nor value the electronic powered rear door...I'd much prefer an simple centrally locked manual rear door. That would have put paid to the cost of the latest failure. Expectations of customers dictate these things though as people tend to compare features when car buying without really thinking about the true benefit to cost/reliability issues. As for the control arms, I put that down to the plethora of speed humps and raised sections at local pedestrian crossings. 2.3 tonnes is a heavy vehicle and unfortunately it does give things like suspension bushings are hard time. I aim to keep my 2014 F-Sport RX for another 6 or 7 years, having already owned it 4 years, as the value to me was in long term ownership and running costs. To date it has proved rather expensive to run...poor on petrol in the hilly area I live in and over complex. I recently re-invested in a new extended warranty after leaving it 6 months after my last one ran out, due to my lack of faith in ongoing reliability based on experience to date. As you say, it ought to capture anything more that happens. People who don't take it out I am afraid could be selling themselves short so I now consider it as a mandatory part of annual running costs, plus the AA breakdown covers all vehicles we own and of course there's the free MOTs. All in all, it's a small price for peace of mind. Had it been any other car other than Lexus, I'd have moved it on, but customer service is second to none and my confidence is less with the vehicle and more that any serious issues will be swiftly dealt with in a professional and dedicated manner by Lexus Cheltenham. None of their other current vehicles appeal to me. The ES being FWD put an end to my interest in their saloons. I was a big Mk2/3 GS fan but things have gone downhill since the mid noughties when their top spec GS models were almost on a par with the LS.

Yes. In 20K miles from date of purchase...and bought at 15K miles, I have cared for my RX almost obsessively, had it regularly serviced at Lexus and driven it regularly but not to any high mileage. It gets between 5 and 6K miles per year. In that time I have had the following go wrong: . Steering rack and motor replacement (under warranty) after a fault was spotted during a service. It had started knocking and makind off noises for a few months previous which was reported; . PBD motor and ECU failure (recently); . 2 nr control arms (suspension bushes shot); . rattles due to trim issue needing work on main dash facia looked at with an attempted repair (unsuccessful); . ECU reflashed and update to main info screen due to recurring lag issues on start up . Axiliiary battery replaced after one year's ownership when it failed almost overnight. It had not been run flat...ever in my ownership until then; For the UK's most reliable SUV, that lot added up to almost 4.5Ks worth of repairs. My previous GS300 suffered similar electrical, suspension, exhaust and other less serious minor niggles, plus failure of several hydraulic tappets at 60K miles. Some night just say I've been unlucky...Lexus dealership thinks so, but I have never before owned any car (I usually change them after 4 years ownership) which has given so much trouble at such low mileages other than a volvo V60 which was plagued with reliability issues (powerpacks to doors failing, throttle body failure, engine mount failures, constant blowing of light bulbs, drive shaft failures). We are fortunate enough to own 3 cars between us. Our Honda Civic has had zero issues in a similar ownership period and same miles. My 16 year old Rav4 has had no serious issues in 100,000 miles of motoring and I will run that one into the ground. It is the single most reliable car we've ever owned. The RX not so much but it is superbly comfortable which matters to me on long runs as I have serious back injuries which mean terrible pain in most other cars if I need to drive for more than 40 minutes or so. You can only speak as you find but cost of purchase or marque is no guarantee of reliability imho. I appreciate many will have had very few issues and are understandably delighted with their RX's. I am not one of those people....but I still like the car and body-work and interior wise it is one of the best quality screwed together and well thought out cars I have owned. Electrical and the off mechanical issues have let it down.

Manufacturers could come up with tricks like retractable side rails that prevent people from getting under the cars in the first place on big cars like RX's. Our way of dealing with it is that we NEVER park the RX at any supermarket or ride and park or any other high risk theft area. We have an old banger used for local runs to these sort of places for things like shopping runs. I gave up parking the RX in supermarkets shortly after buying mine as it wasn't long before I started to notice small dents and scratches appear due to the other "scum bag" part of humanity, the low life shopper with a trolley who couldn't give a damn about other people's property. I couldn't care what happens to the banger. Replacing it costs less than the cost of my current repair bill for the PBD eco & power pack....in fact, RX UNreliability issues have cost me more than any damage or theft...to date. I digress though. The police are not interested in following up car park damage unless they have an open and shut case presented to them with all evidence. I once had a lovely little vRS badly dented and scratched by someone in a red car (red paint left on my car) who side swiped 3/4 of the side of my little Fabia in our local supermarket. It took several requests to get anything out of the supermarket re CCTV and the police were just not interested in doing anything. I am afraid the signs are right. Either park at these places at your own risk or be prepared to take the law into your own hands.

I fitted leads to the auxiliary battery terminated in a proper ipx rated (covered) twin terminal connector which lives permanently accessible in the boot. If the car is parked up for a week or more I simply connect my CYTEK charger to it. No messing about under the bonnet and takes seconds to connect up to. Open rear door, pull connector from under boot liner (where I keep it hidden) connect to charger, close door and forget. Leave as long as you like or just overnight for a quick top up. It's no different in that respect from just about any battery maintenance on just about every other car on the planet. Just don't let the battery get so flat it won't open the rear door. They really oughtn't be left longer than a week without some sort of trickle charge as let any deep cycle battery dip under 50% and you lose efficiency and battery health. Letting older ones dip under 50% charge can kill them off.

I think mine is about 800 pages too so perhaps is the full manual. Not enough for home mechanics but good enough for checks and specs etc.

Well, I can report now on this topic which will cover ALL RX's with power rear doors. I spent an hour at Lexus and had a chat with the mechanic/service manager and there are only a small handful of reasons for a failure of the remote operated PBD, which are exactly as I thought and highlighted above. These are: flat or disconnected battery needs a reset for the remote power pack and ECU for the PBD as per owner's manual; button in glovebox needs pressing; Relay operated by PBD activation switch in glovebox has packed up resulting in no power to remote ECU/powerpack; 30A fuse (box type B or C, I think) blown, needing replacement or fused buzzbar connection (later models but include my own 2014 model) blown needing replacement; power pack and/or remote ECU have packed in. Anyone who experiences problems with the tailgate at all, it can only be for one of the posted reasons above, so check them in that order as the first two on the list are 60 second fixes. In my case, and unfortunately for me, it was found that my rear motor/powerpack/ECU has packed in. I hope you don't get the same issue because the cost is astronomical! I was quoted £1,138 for the replacement of which £745 was parts only. The power pack and ECU are actually under the roof lining which needs removing to get at them so it's quite a big job taking several hours of labour. Perhaps this can become a sticky (or part of it can) as it should cover this not uncommon problem that many owners have reported. I was told that it was extremely rare for a power pack or ECU failure. This is the second "it is extremely rare" repair bill costing the thick end of £1200 I've had with an RX which has only just covered 35K miles so not impressed. I have taken out an extended warranty in case of any other unexpected failures. It goes to show that even if you have a genuinely low miles example, it's a lottery making the warranty very worthwhile folks.

I don't need to as I have paper ones already for mine. It was a comment on new ones coming in without them I was making above.

It's a sad inditement that when one buys a luxury SUV from Lexus there are excuses for not supplying a paper manual. Cost cutting. If it were a green thing then it's gross hypocrisy! Nine times from ten, when I want to reference a manual it's when the head is buried under the bonnet or I'm otherwise engaged with the car looking for something or fault finding. It's bad enough that most modern manuals lack the detail of say a 1980's manual, let alone not supplying a physical one and just not acceptable given the new purchase price.

+1 to all of that (being a past E46 owner too!) added to which most of the latest chargers work on a maximum 4A dropping to a fraction of that as they approach full charge. In reality most battery types will work but a deep cycle of any description will have a longer life...or so you'd like to think. 2 years from my Panasonics was pitiful!