kayuwong

I ordered two sets of caps to repair two bad ECU for my 94 LS400 , one ECU was perfectly working fine and the other still would not pass 2000 rpm. Recheck all joint and trace they all seem good, any suggestion what could be wrong? Thanks in advance.

LScowboyLS

it is possible for an ECU to have a defective transistor or resistor or other component, even a bad microprocessor - since Nippon Denso has never, and will never release the electrical schematic diagram to these ECU's to anyone, not even the dealership, there are some ECU's that can never be repaired!

Yamae

Yes, sometimes a microprocessor is failed and it is almost impossible to fix that ECU because you have no idea to obtain a new microprocessor. I hope yours is not that type of the failure, kayuwong.

But there is a way to fix that using a used processor picking up from another ECU which was not repaired due to the too much leaked liquid and the traces were badly damaged. But this requires equipments and skills. It is beyond the job of a Sunday mechanic. Even professional technicians can't do that easily.

Come to think of it, no dealers fix the ECU replacing capacitors or other components. They just replace the ECU and charge you some big money. Only some people here do the capacitor job spending only 10 dollars + the shipping cost.

LScowboyLS

I would not attempt to resolder an ECU surface mount processor if you gave me the ECU for free!

kayuwong

Thanks guys, maybe I have to give up on that ECU after all, but still happy about fixing one ECU. 1 out of 2. Not bad at all after stressing myself with the solder iron.

kayuwong

Last try, I m gonna put that ECU in oven to reflow the solder.

CAD

I am so happy to report that changing my transmission filter and fluid worked! I love my car

Thank you again, Cowboy! If you're ever in the Sarasota area, let me know, I'd love to give you a huge hug!

LScowboyLS

Yamae, this actually sounds like a good idea for an ECU that has otherwise been given up on for the trash can! (one that is too messed up for new caps to help, due to additional ECU issues)

LexusLexi

Is it true that 98 was a bad year for the LS?

LScowboyLS

No. the LS hasn't had a bad year since it was introduced in 1990 until 2007 when it suffered a serious deep internal engine issue. (valve recall) - this was straightened out with the 2009 model!

The LS has always been one of the world's most reliable cars, and with a fit and finish that is the envy of other automakers, and no vehicle made has a more durable engine, transmission, or A/C system (the three most expensive areas of the car)

I would buy a 1998 in a heartbeat if it was well maintained by the previous owner, always garage kept, and no accident history

kayuwong

I was just wondering my 94 Previa may have same brown caps in 94 LS400. It turns out they are blue color caps with no sign of corrosion and leakage like brand new condition. All brown color cap need attention by now.

LScowboyLS

capacitors are like a tiny battery, and as we all know, batteries have a certain service life, for capacitors it's about 12 years, after that point you are gambling, and once you have leakage, often the ECU circuit board is ruined.

Your Previa capacitors are 20 years old, and therefore likely worn out, regardless of brand or color. I see people all the time who wait until they leak, then they have to buy a junkyard ECU, and then have that ECU recapped, because their ECU has electrolyte damage, which once it begins, eats up your ECU very fast!

kayuwong

Good point. I think it is a nice advice to owner who is driving older car like 15 plus year old should have a good working ECU in storage just in case. Never know when you need one. Go to junk yard and find a good working one for insurance. 50-60 bucks is the best insurance you can get for your LS.

fsuguy

LSCowboyLS, or Yamae,

I would appreciate some of your expert help with changing the caps in my ECU; I opened up my ECU ('92LS400, p/n 89661-50032 or 175000-4111) and can identify only 9 caps; three appear to be the 47mf, 2 are 10mf, 1 is the 220mf, 1 is 100mf and then there are two by what appears to be Marcon(???) that do not have any capacitance values on the can, but show a voltage rating of 35v with temp. at 105c. These two caps are by themselves on the board that lifts up.

My question is do you have any idea of why there are only 9 caps? the box and boards do not appear to be tampered with, and no indication of leakage on the boards! Also, do you thinkt these two caps by themselves are the 15mf ones?

Thanks for any help and insight you can offer.

fsuguy

... forgot to add that the marking on the two capacitors are CE-US 9123 35v