Yamae

Don't forget there are nonvolatile memories in the ECU too. The power disconnection can't erase those stored data.

LScowboyLS

we are discussing why the problem can be solved, and yet the LS400 doesn't behave right for the first minute or some short amount of time and then straightens out smooth as silk, after certain major repairs, seen this happen more than once.

exactly!

Lavrishevo

iTrader: (1)

You know Yaemae, you could make a lot of money if you could produce a performance ROM for the LS400 at a decent price.

How do you think these guys were doing what they do and used to on certain models? When I called a rep in CA for Mines, who in turn asked them in Japan, the reply I got was part related and not being able to get them anymore but this kind of sounds like an excuse...

simondsw

YAMAE, where are you located at as I have a 96' U.S. Spec Lexus LS400 1UZFE that I am wanting to do some work on and would love to get your inputs. I plan on going to Upgarage for parts (Atsugi area off of the 246). Not sure where you are at or if you are in this area. I am having some problems with my car as well and this may be the problem. I am not an electrician and would hate to fry my ECU. Any help would be fantastic and we could use my car for the experiments

wfseward96

That was the root of my question about ECM behavior after removing and mods and what learned parameters where stored in non-volatile memory. Obviously in my case something changed. After installing the first time (after performing re-cap upgrage) it wouldn't even wake up (no check engine light) wouldn't start. Then after putting key in ignition and waiting (unknown duration) it lit up. Then this morning when trying to start same thing. But today subsequent tries it lights up imediately.

As to performance, my up and down idle problem is smooth and very stable. I also had a stumble sitting at traffic light that has dissapeared. The airbag light had gone as well. I had been having trouble codes relating to exhaust/cat system (can't remember off the top of my head) that is gone (could come back im sure, got to fix the "broken EGR pipe" issue).

I'm not 100% sure there is not some hardware issue with ECM and as I have to drive to Miami on saturday I will be testing a lot over the next 2 days. And i still have that link to remanufactured unit bookmarked in my browser Ha!. Brings to mind the scene form 2001 A Sapce odessy when HAL the computer says (paraphrase) "Just what do you think you're doing, Dave? Dave, I really think I’m entitled to an answer to that question?" as dave is removing HAL's vital module's"

LScowboyLS

just to reiterate my warning from post #1 - don't want to scare anyone out of fixing their own car, but don't do this yourself if you are not already good at this type of thing, from post #1:

WARNING - DANGER: this is not a good first-time soldering project, the existing capacitor removal and associated desoldering, cleaning, inspection, soldering and re-inspection is involved and is in some very tight places, you must be experienced at soldering and pretty good at it, or else you need to locate someone who is very experienced at soldering, and then you should buy the special capacitors this job requires, and then let him or her do the operation of replacing them - the NipponDenso ECU in your LS400 is a delicate piece of very expensive electronics. If you wouldn't feel comfortable taking apart a laptop computer and getting it back together successfully, then you probably do not want to be doing the electronic portion of this repair.

johnnyg66

I decided to to get a back up ecu for my 92. 89661-50042. I looked over both inside so no signs of leaks or burns. I put in the replacement and i can say it shifts alot smoother than my original. Mainly around the 40mph area.

So with my original i want to rebuild it. But i am no expert at soldering.

LScowboyLS

that is because the ECU in this car is responsible for all of the shifting intelligence! - the tranny does not have its own ECU.

johnnyg66

Thats right. Its just so interesting that it made a such a difference. So you believe the caps are at fault here?

phlorida

LSCowboyLS - in a recent thread that I cannot find to reference for this question someone stated that the 98-00 ECU's were not experiencing the leaking capacitor issue. Do you agree with this sentiment?

LScowboyLS

I agree that 98-00 have not had the huge issue with it that 90-97 models have

a couple of reasons for this, one of the bad capacitors that was causing the problem (Nichicon PF) was phased out in 98, though some can show up in 99 and 00 ECU's because that was a manufacturing phase out, not a usage phase out until the ECU redesign of 2001

also, 98-00 cars are newer, and this problem happens with time, and is exacerbated by the car sitting, like a Florida snow bird car does, half the year.

have definitely seen the problem on 98-00 models, just to a lesser degree, so far, than 90-97

LScowboyLS

most definitely, that is really the only thing in an ECU that we have seen fail, that could affect the transmission

LScowboyLS

New Rubycon selection chart released

LScowboyLS

it's not always just the caps that have issues, here is a burned up larger wattage resistor from a 92 LS400 (the light blue one burned in half near middle of pic)

ls400geek

Btw, I heard when you change the ECU, you have to get with it the set of keys that match that ECU (at least for my 1998 LS400). Did you have to get new keys? Or can you take out the EPROM of the old unit and replace the one in the new unit with it--i.e. to use your old keys?