Bought a 2008 RX400h late in 2011. It had a very weak 12v battery and it needed a jump start 3X in first two days. So, it should have needed the ISC reset or else it would get crummy mileage yes? In a test, after the three jump starts with no ISC reset, in easy suburban traffic I got 29 mpg and then 26 mpg in mixed suburban/highway use the next day. Had the battery replaced, under warranty, a couple of months later at a dealer that is 120 miles away. Mileage their was 24 mpg on mostly expressway at 70 mph. Dealer put in a new battery and did the ISC reset on their computer following the Toyota/Lexus procedure step-by-step. I confirmed that this was done. I was a pest about it. They did not know about this, but they looked at my insistance and found the bulletin. On the way home mileage was...24 mpg.

Lat week, after the dealer visit, I did another warmed-up car, mild weather, gentle suburban traffic test run. Got 26 mpg.

I don't think the ISC reset did a darned thing.

I have read others saying the same thing from personal experience...ISC did nothing for improving mileage. Some say the 2008 does not need the manual rest, anyway.

I would LOVE to have it be true, as 29 mpg after battery failure w/o the ISC reset is great, but over 30 mpg would be even better, after a reset.

- geo

 

Best I can tell, one person (plus you now) have said they got no improvement (or worse). Everyone else has seen improvement.

As for the 2008 not needing it, there is a TSB stating that it does. I don't imagine Toyota puts out TSB for kicks and giggles. This applies to the original TSB as well as the newer one for 2008 model year.

 

i think the ISC reset works mostly on 06 and 07 vehicles , which existingly has low milage of 18-22mpg and helps to make it to 24-29mpg, i just reset my 07 Rx400h,

existing mileage is 18-20mpg (only city). will update the results in a week.

 

my own anecdotal evidence.

Recently bought a used 2008. Wasn't getting good mileage. best was about 12.4 L/100km according to the display.

Did the ISC reset as per the instructions.

My wife drove it for about a week, then I had a chance to drive it again, I was able to get down to 8.0 L/100 km. Used some mild hypermiling techniques. When my wife drives it, it gets around 10.4

I'm happy with the mileage now.

the ISC reset procedure worked for me. Now, who knows, something else may have been the factor, but as far as I can tell, the only thing that was changed was the ISC reset, and that's assuming that I did the procedure correctly, and didn't in actually do something else.

 

The ISC reset applies to all years (2006-2008). The original TSB came out when there were only 2006 models. I have since found a TSB for the 2007/2008 models and posted it. My own experience when I did mine was an increase in mileage (or a drop in l/100km) from 10 l/100km to 8.1l/100km. That was in the summer. In the winter my mileage drops from 8.1 l/100km to 9.3 l/100km. This drop in mileage in the winter is common on all cars, hybrid or not, but the difference is greater on hybrids.

Weird about your wife...same thing happens when mine drives...lol. The throttle is like a light switch for her. It's either on, or off.

 

funny that is how my little parneli is also...but if I do it oh man.....

 

i just had our battery replaced in my 400h and also did the 80k mile service today so i took the TSB with me and asked Lexus of Louisville to do the ISC reset and they did without question. They also gave me printout showing completed result. my guess is the dealer should always do it for free as i would think it'd be covered under hybrid warranty. either way, dealer did it for free.

 

can people describe where there battery symbol was at prior too and post reset. along with the mileage you did it at. we've got 80k miles on ours and the battery icon always has the level about in the middle of the +/- , sometimes at the very top. never full though. i had dealer do reset but it didn't change the level. is it supposed to reset to full power or my level simply the result of time and usage? i'm wondering if i should keep trying the reset myself as when i tried first time arrows never switched from wheels into battery so no recharge happened. i also read on another forum that the person cycled from the 30-40 second full gas on window, 5 seconds off then repeated until it worked. they didn't stop the process and try again, they keep the engine running and simply paused and then did. anyone else try this?

 

The whole point of the ISC reset is to reset the idle speed control motor, which is a small motor that adjust the electric throttle to maintain proper idle speed. It has absolutely NOTHING to do with the state of charge of the traction battery. When doing the ISC reset the traction battery should be closer to the top end of the charge scale to avoid the engine running constantly after doing the ISC reset as it tries to charge up the traction battery if you did the reset with a low charge. Before doing the ISC reset, simply drive the vehicle agressively so that the engine runs instead of electric only and this will bring the traction battery charge up. You may find that the charge meter goes into the green zone after doing the ISC reset, but that is only because you just spent 40 seconds with the gas engine running while not moving, which caused the traction battery to charge.

So, to make it clear THE ISC RESET HAS NOTHING TO DO WITH THE TRACTION BATTERY OR IT'S STATE OF CHARGE.

If your charge meter stays mostly in the blue zone, that is EXACTLY how Toyota designed it. Their research has shown that the longest life for a battery is obtained if it's not excessively charged or discharged, so they have the system set to keep the state of charge between 20 and 80 percent, which is the blue zone on your charge scale.

By the way, the TSB instructions are VERY CLEAR that you should not run the engine for more than 40 seconds when doing the ISC reset.