Piggyback ECU Lexus/Landcruiser 2UZ-FE with Link G4

The 1UZFE EGR Delete Kit is available for sale here.


New Member
Portland, Australia
Hi all, I've spent the last week on and off wiring in a Link G4 extreme ecu as a piggyback into my Lexus LX470 (Landcruiser) 4x4.
I'm all done but for tapping in a new ECT sensor in somewhere.
I went piggyback so that I could retain the stability control, traction and trans etc, that the link couldn't control (without setting codes) and std ecu would take care of.

Plan is to build up a good base map that runs the std timing curve (just for a starting point), so currently I have not hooked up injectors or coils.

Connected are:
Crank pos.
Cam pos.
IAT (separate sensor)
MAP (Separate sensor)
MAF (not needed but thought I'd monitor it)
o2's (both banks, fronts only)
Wideband o2 (permanent install)
Knock sensors
Road Speed

I've been for a few drives while monitoring everything and observing how the factory ecu runs the show.
First thing, which didn't surprise me was how rich it runs at WOT. Well into the 10:1 AFR's and even flickered a 9:1 in there somewhere. I have an OBDII scanner logging also and there is long term fuel trims of around +7 in alot of areas which may also be adding to WOT.
Timing at cruise via the scanner are around 28 - 32 max degrees at light loads, WOT timing in high teens rising to very low 20's through the upper 3500+.
Here's the reason for this post.
Cruise mixtures are always closed loop (no lean cruise) and swing between 100-150mv to 820mv or so as expected from a factory setup, WOT mixtures as mentioned are VERY rich and show on the narrowbands via the LINK ecu at over 900mv both banks (10:1 ish on WB) nothing surprising, just needs tuning. BUT when I back off and it goes into fuel cutoff the WB goes 22:1 +(max lean reading) however the narrowbands get pegged at 1000mv ( I expect to see essentially around 0 -50 mv), totally opposite to expected.

Anyone have any experience with this or also noticed this?

I'm about to do a cold start, as I think I seen a pegged 1000mv when I first fired up after hooking up th NB's yesterday but a hot start. First theory is the heater circuit affecting it????
Where are you monitoring the O2 readings? With the scan tool from the factory ECU or the link? Is it possible the factory ECU is "making Up" a reading as it cant handle 0-50mv? I have shared the ECT sensor without issue before. Cheers
Ok, thanks for the heads up on the ECT, I tried sharing IAT while monitoring it on the scanner, temp before was 31deg, hooked into signal and it dropped to 9 on the scanner and the Link guage went to 30deg, so assumed couldn't share temps, I didn't try ECT, but am off to have a crack now, thanks.

Also logged most of the std timing map today, so hooked up the coils, setting ref angle is interesting with COP spark with timing light.

Didn't get to the 1000mv fuel cut issue today yet, but will look into again tonight.
ok, figured out the 1000mv thing. It was the settings in the Link ecu going to a default setting if the input was below .05v. I had zero'd out all those but settings but must not have stored to ecu, all good there.

However, I had no luck with the ECT sharing. I'm am be no means an electrician so I have only wired it in to the best of my ability. As soon as I hook up the analogue temp input wire to the factory ECT wire, the scan gauge drops from 75deg to 20 odd and the Link input screen gauge jumps from -40 to only 65 or so. Grounding has me thinking, I have the Link ecu grounded to a structural point in the cabin and not to the engine block, would that effect it much? Any suggestions on how to ground things properly, would be much appreciated.
Had a look over my notes regarding the temp issue. If you have some spare AN channels avaliable you can feed the temp in on these and use a custom calibration table. This removes the second (link) pull up off the sensor and should fix your issue. Cheers
Sorted it this evening with the non temp An-Inputs as suggested, Worked a treat. Thanks alot. Wish there was a "like" button!!
Also hooked up the injectors, so I'm fully wired now.

Started tuning fuel with a bit of manual editing to get in the ballpark and then went for a drive with the auto-tune going and it's now trimmed most of the part throttles around the cruise loads.

To calibrate the ECT custom table I just started from cold with the scanner going and the Link showing input volts and built the table up as it sat there idling, warming up, unfortunately I missed the 20 and 30 deg points but got 40 through 90 and can see a pattern so guessimated the colder and hotter points until I get into it again when it's cold again.

Thanks again for your input Gloverman
hi @tnt76 by chance do you have the wiring diagram? I'm thinking of the same, running dual ECU with Toyota Denso 89666-60711 and thinking of Link G4 or MegaSquirt MS3Pro for AFR calibration.