nopcbs

Bought a 2008 RX400h (18,500 miles) in December. I had to jump start it three times in first two days we had it to get it to run as the 12v battery was bad...probably had a bad cell. It did behave itself after that for 1.5 months.

Took it to Lexus of Ann Arbor last week and they checked the battery, diagnosed it as bad and replaced it with a new one under warranty.

Now, I had read all about the Lexus tech. bulletin staing that the ISC has to be reset after you have a battery failure or replace it. So I made sure that the Lexus service people knew I wanted this done. They had never heard of this, but at my insistence, they looked and found the bulletin and then followed it, step by step, after installing the new battery. (Interestingly, a salesman said he had heard about this.) Anyway, I was expecting a significant improvement in mileage after the ISC was reset...it has been pretty mediocre. Here is the before and after mileage for the battery replacement and ISC reset.

Before: 23.9 mpg highway @ 70 mph on cruise
After: 23.8 mpg highway @ 70 mph on cruise

Before: 18 mpg true city (not suburban, city)
After: 18 mpg true city (not suburban, city)

In other words, the ISC reset did absolutely nothing. Zip. Nada.

When we first got the car in December, it was pretty warm (high 40's) and in suburban-type driving we got 29 mpg one day (20 mies) and 26 mpg in mixed highway/suburban driving on another (40 miles).

In cooler weather, mileage has been disappointing. Little better, if at all, than the 2004 RX330 that this car replaced.

Whover said hybrids and cold weather do not mix was right.

- nopcbs

rcy

Your December experience - 20 and 40 mile drives are not long enough to give an average MPG. Same with your experience after the ISC reset.

Every vehicle experiences reduced MPG in the winter due to several factors - the temperature and winter gas being the most obvious. The effect is greater on a hybrid, though, since the engine runs more in colder weather than it does in hotter weather. I regularly drop from 8.1 l/100km to as high as 9.5l/100km when it gets cold.

Wait till the warmer weather and you should see an improvement.

When it comes to the ISC reset, I can't think of one person here or at lexusownersclub.com who hasn't seen improved mileage after doing it themselves or having the dealer do it.

nopcbs

The 20 and 40 mile samples were adequate for estimating avg mpg for THAT KIND OF DRIVING in that weather. I see this all the time and you can, too. The mpg estimate that my wife gets on her short commute to work is the same (within a 1 mpg range) from early in a fillup to the very end when she has to refill. I am talking about the in-car display, which seems to be accurate based a just a few fill-ups and manual calculation. At most, it is 2-5% off...at most.

As to your other points, I have seen several instances on the two Lexus forums that I frequent of RX400h drivers doing the (arcane) ISC reset themselves and seeing no improvement. I think one guy saw a worsening.

Now it may be true that in cold weather (and certainly in terms of highway mileage) this ISC reset does little or nothing. But the fact remains that I did see those two very high (in my view) mpg results AFTER our battery failed to start the car three times and I had to jump it. Maybe a weak battery, like that, is not enough to require an ISC reset, but that is not what I have read.

I am optimistic that when it gets warmer we will see an improvement, we always did with our RX330, but I fear that the 26 mpg city estimate is going to be a chimera in true city stop/go driving. I think you can get that in easy suburban-style driving (few stops and under 45 mph with gentle acceleration), but I'll bet an RX330/RX350 would be in the low 20 to mid 20's under those conditions.

Here is an interesting sidelight. Consumer Reports tested a 2.8 L BMW X3 recently and got 30 mpg out of it, highway! (And 15 city.) CR rated the 2007 RX350 at 13 mpg city and 26 mpg highway, the 2012 RX450h is rated 22/31(!), the 2005 RX400h 16/29, and the 2005 Highlander hybrid 16/28.

So our RX400h gets the same CR numbers as a 2.8 BMW X3...which is actually very disappointing. When I shopped the RX400h I thought the CR city number must be wildly off, but now I think it is spot on. What confirms that is that their numbers for the RX450h are spot on with the EPA estimates and that the last gen Hylander hybrid (a powertrain twin of the RX400h) gets the same very bad city number.

On the other hand, some owners report very high city numbers...rivaling an RX450h.

All very confusing.

- nopcbs



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rcy

If you've driven 2600 miles and the trip computer shows xx mpg, then you reset the computer and drive 20 miles and get yy mpg, that is not a direct comparison.

When I get home and can use a computer, not a mobile device, I bet I can find and post more links where the ISC reset led to improved fuel economy than ones that didn't.

nopcbs

but that does not mean that they are comparing apples with apples.

If somebody does the same commute every day with the same traffic pattern and same weather and then does the ISC reset and compares before/after, then I think, that result would have some bearing. If there is a case like that, I'd love to hear about it. Hey, I want to believe in magic, too.

On the other hand, just what, exactly, is this magic that an ISC reset is supposed to do that it could give the "fabulous" mileage improvement? It really does not make sense that Toyota would design a car that way, which is to say, a 12v battery failure or replacement requires that you go back to the dealer and have them hook up their computer and run some obscure procedure (that at least some dealers never heard of) or run an arcane series of actions yourself on your $50,000 hybrid...or else it gives crappy mileage? It borders on bad engineering. No, actually it is bad engineering...if it's true. I don't think it is.

- nopcbs

Cruiter

I'd call you by your 1st name but you didn't list it in your details.

Just like on our RX 450h board, the cars will perform with varying results depending on the driver, driving conditions, weather and temps, etc. I can't speak to the ISC reset service, I wasn't there. But to get the 'hybrid' mileage you have to adapt a different driving style than you had prior to driving a hybrid. They can and will give great mileage but they need to be driven differently. I had to develop a new mindset when I got mine, but it didn't take long to realize the advertised mileage was indeed possible if I changed my (aggressive style) driving habits.

To get the Hybrid mileage, you actually 'have' to accelerate as if there is an egg under your foot, maintain a steady speed, and decelerate as early as possible. I've even removed the radar detector as speeding does nothing but reduce the miles per gallon. So far, I've not been late and I've noticed more of the country I pass through .

If you leave the car outside in the winter its worse for several miles because the traction batteries are stone cold and won't give their best performance until they warm up. If you drive short commutes like 3 to 5 miles mileage will be horrible but it'll be the same for any car.

You mentioned you got 26 + in the city, that's not bad for your model, especially in the winter. And as RCY said, the way you're figuring it is not giving you a mean average. Mileage figured over two or three months would be much more accurate. But if you feel there is a problem with your reset, then by all means return to your dealer and ask if they'd check it for you.

RE: engineering, IMHO, these are some of the best engineered cars available at any price. But like you're entitled to your opinion, I am as well. And one of my retirements is from the Auto business. I never worked for Lexus but my wallet say's I'm biased toward them. My RX 450h isn't my 1st one.

Stay with us and let us know how it goes.

nopcbs

Thanks for your comment.

This is our 3rd Lexus. First is a 1992 LS400 that we have had for 19 years. The second was a 2004 (early production) RX330 that we had for 5 years and still would except a woman driving HUA totalled it out in November 2011. (I'd still like to get my hands on that idiot.) Both are/were GREAT cars. That's why we replaced the RX330 with another RX of the same generation, just the hybrid flavor.

I addressed the avg mileage question. My wife gets the same average mileage at the start of a tank of gas as she is getting when it is near empty and she has to refill. You can do this if your driving pattern is uniform and if the weather is pretty uniform. Both apply since we got the car in December. This is not true for everyone as some have much more variation in driving conditions.

That day we got the 29 mpg "city" was an unusually warm winter day, a Saturday, and I was driving the car like L. T. Baloonfoot would. I wanted to give the car every chance. The incentive was that I did not want to have to admit I paid an extra $3,000 for the car over a comparable non-hybrid RX350 and an extra $100 a year for insurance for nothing. It worked. That day. This was probably a best case suburban-style driving day. It was not like my wife's work commute by any stretch. The point was that even without an ISC reset, the car can make really good mileage numbers after 3 dead battery incidents. The next day's highway/suburban-city number of 26 mpg over 40 miles just confirmed that.

The ISC reset was done BY-THE-BOOK. The techs had their computer connected to the car and were following the steps directly out of the service bulletin, on their computer. I think we can take it for granted that they can follow instructions provided by Toyota.

Again, thus far, with a new battery installed, the ISC reset has done absolutely nothing to the mileage we were getting before the reset. Nothing. Maybe with T's running from mid-20's to upper 30's you just don't see an effect, maybe. Hope so, because that would mean a very pleasant surprise come spring.

The style of driving you describe is not foreign to me. I use it all the time with my 2006 E320 CDI in the summer months when it comes out of winter storage. I am still trrying to get it to deliver the 26 mpg city I was hoping for w/o luck.

Finally, I bow to no one in my respect for Toyota engineering. That's why I just don't buy this ISC resetting thing. That would be such a kludge for them. I don't think they could hold their heads up in front of German and even US engineers at an SAE or ME conference if they did such a kludge.

- George

rcy

When I first got my 2006, it was summer (June 2009). My commute is the same every single day - I work seven days straight, then a series of days off them seven days again - repeat over and over.. I reset the computer at the start of the seven days when I first got the vehicle. Mileage was 10.1 l/100km. After that week, I spent my days off perusing the Lexus forums and hybrid forums, which is where I found the ISC reset instructions and the TSB. My next set of seven days working, I reset the computer and over that week mileage was 8.1 Other's have seen similar gains.

Per the TSB, "Engine runs too long or more frequently than normal. Reduced fuel economy" After the ISC reset, when the engine doesn't run too long or more frequently than normal, the only result there can be is improved mileage. This is the 'magic' I guess???

I still don't quite understand what exactly you're griping about. Are you just unhappy with the fuel economy or are you saying that the ISC reset is a figment of someone's imagination, or made up by someone other than Toyota.

The TSB is readily available for download, Toyota created the TSB and the vehicle, the dealer found it in their files (just because they were not AWARE of the TSB doesn't negate the fact that the TSB exists and is applicable - it's sometimes mind boggling the amount a dealer DOESN'T know). So I don't understand the point you're trying to make when you say "It really does not make sense that Toyota would design a car that way, which is to say, a 12v battery failure or replacement requires that you go back to the dealer and have them hook up their computer and run some obscure procedure (that at least some dealers never heard of) or run an arcane series of actions yourself on your $50,000 hybrid...or else it gives crappy mileage? It borders on bad engineering. No, actually it is bad engineering...if it's true. I don't think it is."

By saying, "if it's true. I don't think it is." what do you mean? You don't think the TSB exists or applies? Here it is in case you haven't seen it.

This particular .pdf says it's for 2006 models, but I've also found a TSB for 2008 models...see here http://us.lexusownersclub.com/forums...=&fromsearch=1 This post also reminded me that aside from the TSB, the procedure is also in the service manual. I have the service manual on disc and can confirm that it's there.

nopcbs

...that no one has ever explained what this magic is that is supposed to happen when this mysterious ISC reset is done. Further, in my own 1st hand experience after 3 battery failures and no ISC reset the car managed 29 mpg city and 26 mpg mixed city/highway. After the reset the highway mileage is EXACTLY identical to what it was before the reset (over 120 miles each way). This week we had a warm day and with a warmed up engine battery our little beauty managed to deliver 26 mpg in a suburban-style run. I call that a near match for the post-dead-battery 29 mpg I got last year under similar conditions.

Also consider that in this age of static memory, there is absolutely no excuse for Toyota storing operationally critical information in anything other than non-volatile static ram in this car. I know you have to re-index the windows after a battery replacement, but that is hardly operationally critical. Engine not running right is.

But OK, let's say that the Japanese engineers screwed the pooch and some critical information goes "poof" after a battery change. Don't you think that the car would just re-learn that by itself?

But OK, let's say that they blew that one, too, and you need to do this ISC reset...that does something or other. So how come the best mileage I have seen, and very good mileage, was after three dead battery incidents and no ISC reset.

Finally, I am not the only one to report no benefit after an ISC reset. Some have even reported worse mileage.

The dealer who did not know about this trick is in a very large, very affluent, very liberal college town loaded with tree-hugger types who buy hybrids. Their not knowing about this tells me that it is not a big deal.

- grl

rcy

So, Toyota/Lexus just put the TSB regarding the ISC reset out because they had nothing better to do? I have the factory service manual on DVD and the procedure is well documented there, and the service manual was available before the TSB was issued. My guess is that technicians at dealerships were missing this procedure when working on a 400h, hence the TSB was issued as a heads up for them. There have been owner's who complained of a rattling noise from the transmission at idle, which is one of the symptoms the ISC reset deals with. Maybe after the Toyota Tech Line got several calls from dealers regarding this rattling noise, someone clued in and issued the TSB. Regardless, it's an official Toyota TSB, specifically issued for the 400h. Why do you have such a hard time with it?

The fact that your dealership/town is filled with tree hugging, liberal, affluent hybrid owners is really a moot point. Just because someone is affluent and liberal and drives a hybrid doesn't make them a genius, nor an expert on Toyota hybrid technology. I would think that Toyota would be most knowledgeable regarding their technology, and THEY are the ones that have issued the TSB for the ISC reset.

Do you have some other explanation for the existence of the ISC reset TSB? Have you even bothered to read the TSB, as the 'magic' is pretty much explained in the TSB, specifically, the engine will run longer and more often than normal. Longer and more often idling should lead to worse fuel economy, no?

I'll post the pertinent sections here...

"When the 12–volt battery is disconnected or is depleted below 7 volts on 2006 model
year RX 400h vehicles, it is necessary to perform the ISC Learning procedure to
re–initialize the idle speed control. The information in this TSIB relates to this procedure."

"It is important to perform the ISC Learning procedure anytime the 12–volt battery is
disconnected or the voltage falls below 7 volts. This procedure allows the I.C. (internal
combustion) Engine to re–learn its optimal idle speed during the initial engine warm–up
cycle or charging the HV battery. If this procedure is NOT performed, the following
customer complaints may occur:
Engine runs too long or more frequently than normal
Reduced fuel economy
Transmission gear “clatter” noise at idle is more pronounced"

nopcbs

The point of describing the type of town that the dealership is in is that this dealership is likely to sell more hybrids than your average Lexus dealer. The RX400h is a slow seller vs. the non-nybrid. and they didn't know about this supposedly important ISC reset.

I've seen the TSB. It is very strange. I was ready to believe that it would do what some in say it does...massive increases in mileage. I literally forced the dealer to do it it it did exactly NOTHING for my car. Zip. nada. And that's after a battery change.

Further, you will find conflicting statements in this forum as to whether it does anything for post 2006 RX400h's. Some claim that newer models self-reset.

I have a hard time with it, because it didn't do a darned thing for my 2008 RX400h! This would not bother you...even a little?

- geo

rcy

Well, it's right in the service manual, so despite being a tree hugging, affluent, hybrid driving neighbourhood, someone at the dealer is not doing their job. When I mentioned it to my dealership when I had my inverter replaced, they told me that when working on vehicles, there are step by step instructions in the service manual that the technician follows. One of the steps (depending on what work is being done) is the ISC reset. I can copy and paste it right from my service disc if you want.

My guess is, most technicians don't read the steps in the service manual, because they already know what they are doing, hence, they don't know about the ISC reset needing to be done when the battery is disconnected (for my inverter they probably did read the directinos in the service manual, because they had never replaced one).

I'm sure they don't read the service manual when changing a battery, for example. Or look at a timing belt change - the service manual outlines the steps, one which is disconnecting the battery. When it comes to putting it all back together, the service manual outlines everything that needs to be reset - the power windows, the sunroof, the power hatch AND the ISC reset. But most tecnhicians don't need to follow the service manual for a timing belt change because they can do it from experience. So Toyota puts out the TSB to alert the dealerships to this specific step required on a hybrid.

As to it not being needed on post 2006 RX400h - the original TSB came out in the 2006 model year. That's the one originally posted here and elsewhere on the web. I have since found a TSB that specifically mentions the 2008 model year. It's posted here...I'm sure you've seen it.

Would I care if the TSB was done on my vehicle and it made no difference - nope, couldn't give a damn. Toyota says it must done when the battery is disconnected, I want it done. They know my car better than I do.

rcy

Here is the TSB for 2008 models for everyone's convenience...

nopcbs

OK, read what it says folks.

The ISC reset "reinitializes the idle speed control". Doing this "allows the ICE to relearn its optimal idle speed during the initial engine warm-up cycle or charging the HV battery".

It then notes that not doing so may result in customer complaints of engine running too long, reduced mileage, or transmission gear clatter.

So we are resetting the idle speed to "optimal" during the first engine warm-up cycle after the battery is changed. If the idle is initially too low and not corrected, you may have HV charging problems, makes sense. If it is initially too high, you may see a small decrease in fuel economy. I can see the transmission clatter being a problem if the idle speed is significantly too high (noise as the transmission engages).

Now NONE of the things that Toyota mentions as reasons why you want to have the ISC done are going to lead to the drastic fuel economy changes that people claim they get after having an ISC reset done. We see claims of 20% and up fuel economy increases. No way an idle speed correction can do that. The engine idles only a very small portion of the time the car is driven and even then it is just sipping fuel. You get your real fuel consumption under acceleration or constant high speed and that has zip to do with idle speed settings. Read what Toyota says and then think about what the words mean. They are telling you what the procedure does. It is minor stuff.

Further, I'll bet you that what Toyota is telling the service department to do after a bad battery or battery replacement "happens" (reset the ISC) is something that the engine computer will do itself, over time, after battery service, but they want to avoid the customer experiencing the noted stmptoms while the engine control self-adjusts by having it done on the service computer at the time of service. That makes perfect sense.

This also explains why a major Lexus dealership service department can not know about this. Not doing it may result in a small short-term mileage decrease, but the car will self-adjust, probably quickly. If you had dealers not performing this and it leading to major fuel economy decreases, you can bet on it that customers would be coming back and that would lead to another TSB reminding service departments to not forget to do this. That would get their attention, I submit.

Designing the car so that after a battery change mileage goes to hell big time and the car cannot adjust to the new battery w/o being put on a service computer makes absolutely no sense and would be gross engineering incompetence. Not likely from Toyota.

- geo

rcy

I'm just going to give up on this. You have your mind set that it•s a waste of time and nothing is going to change that.

However I will point out a few things. I doubt it's a mass hallucination for those that have seen a mileage increase. Many have noted that the ICE does not start as often or as easily (no need to use gas pedal like there's an egg sitting on it) during normal driving after the ICE has warmed up. The transmission gear clatter they are talking about is not as you engage the transmission, it's while the vehicle is sitting still and idling, in park or drive or reverse. If prior to an ISC reset the engine idles longer, doesn't shut down at stops or while coasting, or engages immediately upon acceleration then I do the reset and now it idles less, shuts down more often, and I can accelerate from a stop purely on electric, I am bound to see mileage increase.

I highly doubt it's self resetting as there have been improvements in fuel economy after doing the ISC reset after months of driving. If it was self resetting wouldn't it have occurred before months had gone by?

As to gross eengineering incompetence, look no further than the 1mz-fe engine sludge fiasco, the carpet floor mat / run away vehicle problems, the inverter recall, the pulley recall, brake switch recall, rotting frames on their pickup truck.....really no need to list more, the point being that Toyota is not infallible as many like to think.

The TSB exists for a reason. Toyota says it needs to be done under certain conditions. As I said before, it's your vehicle and you can do as you wish. I still maintain that Toyota knows their technology more than you, me or any technician at any dealership, and if they say the ISC needs resetting I believe them.