Pinout for Ecu 89661-50170

josh bee

New Member
Hi guys
I'm having a lot of trouble locating a diagram for my ECU, its a 89661-50170 (34-22-16-28 layout) from a UCF 1X Celsior.
The loom had been wired for a later (UCF2X) ecu that didn't match the motor and I am now just trying to verify if my 28 pin plug is wired correctly as I have found there are differences between the years and I am unable to start it. At the moment I have this:

# 9 grey IGSW 12v w/ ignition
#13 green-red MREL 12v out to EFI relay
#14 black-yellow BATT 12v constant
#16 BK brake pedal
#22 and #23 B+ 12v out from EFI relay to ECU

I seem to have fuel pressure (fuel pump primes) and I have spark but it only cranks, won't fire. Even on aerostart.. Oddly enough I did have it running with the 28 pin plug (only) wired in its old config and plugged into the old (ucf2x) ecu but cannot get it running on the single ecu with the new config (nor the old config). Basically just moved MREL from #24 to #13. Logic tells me its something to do with powering the efi or ecu as thats essentially all that's changed since I had it running with the 2nd ecu piggybacking? The only error code I get is 78 - which is traction control or something (not running it, don't care)
It's in a hilux too

If anyone has a suggestion besides burning it, or knows where I could find/buy the diagram for this ecu please let me know!


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It must have 1994-1996ish Lexus LS400 which uses pretty much same pinout. The only difference is maybe that Lexus may have EGR valve for USDM specs, and JDM Toyota has a sensor of hydro fan fluid level.

In addition, you can find '96 LS400 diagram here at Lextreme, it comes in 4 sheets. Look at the main page, not the forums.

josh bee

New Member
Got it sorted! The pinout was correct, I had inadvertently flooded the motor in the process of testing. Blew the fuel out and changed the plugs (to copper ones) and she fired up as soon as I turned the key! Only error code I'm getting is traction control (which isn't connected) so I'm stoked! Thanks for the input guys


78 is fuel pump control, they usually fire that when they sense that the fuel pump computer is missing