Lexus-Toyota V8 UZFE Forums

Ok. I rebuild the later ones. There is a trick to getting them apart but we should check the wiring first. The diagram is a little small on my phone but it doesn't look right to me. Which ecu number do you have? It might be possible to check iac wiring via the engine mounted diagnostic box.

I did verify 14vdc, whilst running, on the black/red sensor power wire at the diagnostic check port. As well as the vacuum solenoid valve and EGR valve. Also, I have no error codes in diagnostics. I will be taking a voltage reading at the IACV connector when I get home today from work and will report back here

Ensure you check after the engine is turned off as well.

I have verified 14vdc at the two middle pins of the IACV. Also, when the key is turned off, I can hear the fuel pump and relay stay on a few seconds after. So the mrel circuit is working.

Did you confirm that the IAC has power after the key is turned off? If the engine is wired correctly the fuel pump does not run after the key is turned off. Does your fuel pump run when the key is turned on or only once engine is cranked and started?

Verified 14vdc after engine shut off. The fuel pump runs when in the on position (not ideal, I know), if you look at that diagram in the link, mrel runs my fuel pump relay. So the mrel circuit controls my pump. +b and +b1 are on the same blk/rd sensor power wire and that’s supplying my IACV. The Ecu grounds each coil to change the IACV opening. Is that right?

Yes I saw the mrel does the fuel pump. This is wrong. What ecu number do you have? The main efi should supply the +b , +b1 and the sensor power supplies which include the IAC. Yes the IAC controls the two pairs of windings. I know you have an early ecu but which number?

Ok I'm using my laptop and can see you have an early Gen 1 ecu. By the looks of the diagram it's manual. For a start I remove the NSW wire completely. The fuel pump relay can be triggered by the ECU. Ideally you use a Circuit opening relay and a fuel pump relay like the factory but you can get away with using the both FC and FPR linked together triggering the fuel pump relay.

It's a negitive output with other side side of the switch being ignition , that way the fuel punp will turn off when the key is turned off or the engine is not running.

So mrel needs to open a relay for +b and b1? And then the fc and fpr wires can be tethered and used to power the fuel pump? Also, can explain how to open up the IACV I have? (No bolts for the motor)