LScowboyLS

the highest failure incidence has been in 92-97 models, so far - but these capacitors were used through the 2000 model, although Yamae indicates that the design of 98-2000 ECU is less hard on caps, perhaps giving these models some additional lifetime.

but keep in mind that all electrolytic capacitors get old, even if they are not of a defective series, and some Lexus models are now 24 years old

capacitors are much like a small rechargeable battery, and like all batteries, they have a life, and it's not meant to be 20 years!

KahnBB6

iTrader: (5)

Thank you. From this and Yamae's comment I will consider sending it out for new capacitors soon in that case. I'll try opening the top plate to check the logic board first, however. The ECU currently in my car is a year older than this turbo ECU and so far no issues-- but from what you say I take it to mean that replacement is inevitable.

Earlier in the thread I read that allowing an ECU to sit unused compounds the problem which is why I asked.

LScowboyLS

I see you have a 93 SC300, and actually that has been one of the models and years with some of the very highest incidences of capacitor failure, from what I have seen. SC400's from that time are equally failing, whereas 95 and 96 may be the two most high failure LS years although 93-94 on the LS are not far behind.

Also, Florida is the most common state for ECU cap failure - heat & humidity combination?

qha_vn

i got mine replaced. the old caps do not look bad or have any visible liquid leakage. I havent put it back in my car however, need to find some time.

LScowboyLS

look at the bottom of the caps carefully, the area between the leads should be bone dry, there will be some or all of them with a wet or oily look, I have never seen a complete set of ECU caps that were not leaking, and I have seen hundreds of sets.

qha_vn

yes closer look shows oily base. these are the 10 caps replaced.

Yamae

Most of those are Nippon Chemicon's standard 85 degrees C capacitors SM and SME series. These have higher ESR and the capability for the ripple and noise rejection are not very good also they don't last long.

LScowboyLS

I am starting to see many cases of LS400 ECU's where the board looks fine on initial inspection, and then after the capacitors are removed, the bottom bungs are already wet with leakage that could not be seen with the capacitors still mounted.

So it is beginning to appear that potentially all 92-97 ECU's have at least some of the capacitors already leaking, kind of a ticking time bomb, so to speak.

If you have a small dental mirror and a good headlight, you may well be able to see the wet or oily bottoms of the caps with them still installed.

qha_vn

i plugged it in today and gave it a test run. to be honest, the difference is not really day and night unfortunately. however, the car SEEMS more responsive to pedal and a little smoother at idle and when I shift from P to D or R. But dont get me wrong please, I never regret replacing the caps.

LScowboyLS

I think you will see more of the ECU capacitor improvement once the new ECTS is installed

qha_vn

ECTS? sorry dont know of it

LScowboyLS

Engine Coolant Temperature Sensor - you just ordered one!

qha_vn

yes I will replace it shortly when the timing belt kit arrives. shipping is a bit slower during Lunar new year

qha_vn

I would like to update status and say BIG THANK to the LScowboyLS and those who contributed to this great post.

my first run test was about less than a mile from home and as I mentioned earlier, the difference was not noticeable.

I've started to see the improvement today when I drive a longer trip of about 10 miles to work. I feel noticeably faster response from gas pedal and a lot smoother shifting, iding. i guess the new ECU needs some time to "learn and calibrate" the input sensors and driver's behaviour before providing the best performance.

I am going to recommend this "tune-up" to a group of about 20 guys driving LS400 here in VN.

Superfast1

I went ahead & replaced the 6 electrolytic caps on my 97 LS even though I don't have a problem with my ECU. My OEM caps are the brown ones. Once removed & inspected, they're in pristine condition & bone dried all around & underneath the caps. I've also measured each one w/ a capacitance meter & they're all within spec. Getting to the ECU & removing the caps are not a simple task so it's not a job for everyone. These are electrolytic caps so they're mainly used as by-pass caps which means their main function is to filter out ripple voltages from the DC lines (12 Vdc & 5.2 Vdc). Based on my result, if your cars are 97 or newer & run great without any known problem with the ECU, I strongly recommend you should leave them alone. This may go against LSCowboy's & Yamae's recommendations as they're great assets to our Lexus community but like the old saying: Why fix it when it ain't broken? Perhaps, Toyota has used new batches of caps for 97 & newer models so they're less prone to failure? You're the owner of your car so do what you think is best for it. I bought mine when it was a year old so it has been with the family for 16 years now & has just passed the 200K mark. It has been a great machine with practically zero defect.