gregppg

Can you use an ECU from 1992 to work on a 1991 LS 400? i found one in a wrecking yard with 50000 miles on it i figured i would replace the caps on it and use it.

Amskeptic

I believe the model year is not the problem, but TRAC vs no TRAC.
Other opinions welcome . . .

gregppg

Thanks, this one is listed w/Traction and my vehicle has Traction so thanks ill give it a try.

gregppg

I have no Battery voltage at the fuel pump relay, it would run and start fine for 2 days and then not start and run rough, and the run fine, but now it wont start at all, i tried to spray starting fluid but nothing to see if was the fuel pump or lack there of, once and a while the starter will stick slightly, the shifter is wierd somtimes so if figured from the other thread that the ECU has the bad capacitors.

oldskewel

iTrader: (1)

ECU capacitors is not the first thing I would think of based on your symptoms. There's a lot of info on this site for no-start fuel related issues. Here is a page with helpful debugging information if you've got a multimeter and can follow simple circuit diagrams:

https://www.clublexus.com/forums/ls-...ml#post9777959

I would trace where voltage should be, vs. where it is, all the way through the circuit. That also shows how you can bypass the ECU to power the fuel pump. Pretty easy tests, vs. considering swapping ECUs that may not be a perfect match.

And regarding the ECU, it would probably be best to read the actual part number off your ECU and see if it matches the donor. Yamae had a nice thread going on here, supporting the ECU capacitors thread, where he was keeping track of all the different ECU part numbers throughout the years.

Year probably matters. TRAC definitely matters. Air suspension maybe as well.