geoprz

1992 LS400 255KM

My check engine light and TRAC light came on simultaneously the other day. I checked the codes

Engine codes 25- Air-fuel ratio lean malfunction 28- Main oxygen sensor signal (on right bank) Transmission code 63- Open or short circuit in no. 2 solenoid valve
TRAC code 51 - Problem in engine control system

Im assuming engine code 25 and 28 are related to the oxygen sensor but why did the TRAC light come on at the same time? Is it coincidence? or due my engine codes have something to do with the TRAC code?

LScowboyLS

something sounds a bit fishy here, all of those codes at once, I would try clearing the codes and see which ones come back

clear all stored codes by removing the 20 amp EFI fuse for a half an hour, or even better, the negative battery cable

geoprz

I did remove that fuse for a few minutes not a half an hour and they never went away. Then I also even removed the negative cable for a few minutes and nothing cleared...

LScowboyLS

well they have to clear! - they might become set again, once the car is cranked, but they certainly should clear, or that is a whole other issue

code 63 - Open or short circuit in no. 2 solenoid valve is a transmission code, not a TRAC code!

do you feel like pulling the ECU and taking some pics of the inside of it? - we need to see if it is leaking, which is becoming an epidemic here on Club Lexus!

Attachment 498614

geoprz

what do you mean by this " they might become set again, one the car is cranked"

Should the key be in the on position or not in at all while trying to reset the engine light?

LScowboyLS

remove key when resetting engine codes with negative battery cable disconnection

geoprz

see i did that and they never cleared

LScowboyLS

some codes can get set as soon as the key is turned to the run position, and other codes require the car to crank up and run before they can be set again

also, did you move the jumper to the other position to check for TRAC and ABS codes?

geoprz

I just checked it and TRAC code 51 - Problem in engine control system

what the heck is going on here....

LScowboyLS

here is my vote

think about these two pieces of evidence:

1. all of your crazy unrelated codes have only one thing in common to the O2 sensor, the transmission control and the TRAC control - the ECU

2. LS400 and other Lexus/Toyota ECU have a very common issue with leaking or failing capcitors in the ECU

geoprz

So finally took out the ECU. Looked through it up and down 10 times and no damage is visible anywhere. Looks perfectly fine!

Don't know if that's a good thing or bad thing. I'd like to solve this mess.

What's my next step?

LScowboyLS

well your year of Lexus has had a really high prevalence, and all capacitors go bad after a given period of time, they are like a battery (they are kind of a mini-battery electrically) and as you know, batteries eventually just go bad.

the ECU caps can be going bad before you see visible leakage

here is a typical story I hear from people on these capacitors, and this one happens to be from my own car!

when my car started having issues, I thought of the ECU caps, as I had seen and fixed this problem in other cars in the late 1990's - so I took out my ECU, opened it up, everything looked perfect, put it back in and kept searching for the problem, it was driving me crazy because everything was checking out perfectly elsewhere in the car, this went on for about 4 or 5 months or so.

I kept thinking, this seems like leaking ECU capacitors, but would answer myself "No, I already checked for that"

Finally one day, I forced myself to pull the ECU again, because I was at my wit's end with the car, which was getting even worse, and this time, OMG, there was pretty massive damage from the leaked electrolyte of the failed caps, the circuit board was almost unsalvageable!

So in the course of just 4 or 5 months, my ECU had gone from looking like new inside, to damaged almost beyond repair!

There is a current thread here in the LS400 section of Club Lexus with pics titled "Ecu" with someone who has let his go too long! - Now he has to buy another ECU used, and then have that new ECU's caps repaired!

So I am not saying it's is 100% chance of being your ECU caps, but it is a high chance, and something you need to get done proactively anyway, which will be be a smart move before a lot of preventable damage is done.

geoprz

Thank you very much LScowboy! You speak the truth and I will still fix those capacitors before its too late!

Really hope it will solve the issue, it would be a bonus if it fixes all those codes.

Do you think o2 sensor is a separate issue though? Or still possibly related to the ECU capacitors?

LScowboyLS

once the ECU caps start to go, the ECU may throw random or nonsensical codes, or stop communicating altogether, this is why I like to take the ECU malfunctioning away as a variable, first thing, since it is key to have it healthy since it helps you diagnose the rest of the car!

geoprz

I was thinking of buying a ECU from eBay. Switch it up hopefully for one that fixes my issues and then fix the old one whenever