R32 Attesa Problems - Need Help

[Samuel Leonard]

I have known for a long time that my 4wd doesn't work. with the ignition on and trying to do the attesa bleeding procedure my pump will not ever come on.

i have 2 issues i believe, firstly, my pump has siezed up and i know this because i have bypassed the big relay in the boot and can not get the pump to start even whacking it the same way that frees up a fuel pump usually whilst bypassing the relay and giving the pump power.

but i believe it has siezed because the ecu is not ever closing the relay. i have tested the relay on the battery and it is very noisy when it clicks closed.

i can not hear the relay click closed when the ignition is turned to on which i have heard many other r32 gtr 4wd systems prime the pump every ignition cycle.

i'm not getting any codes unless i induce a fault like unplugging the pump or a relay, so my ecu believes all is well and my front torque guage is operating correctly.

my theory, my attesa ecu or wiring loom is stuffed and therefore the relay never closes and my pump is never getting used and that's why it has siezed up.

any opinions would help. i should try another ecu and see if it closes the terminals on the relay and when all else is working well i should replace the pump, right?

[Samuel Leonard]

update: i went out and removed the air bleed connector behind the drivers side kick panel. i could hear the relay clicking when i turned the ignition on. it got dark so i couldn't test any further. hope to continue diagnosing it tomorrow after work!

[Samuel Leonard]

Looked into this further, I heard the wrong relay clicking. Not the 4 pin pump relay, the other 5 pin relay was clicking. The 4 pin pump relay works correctly, (bench tested and tried in another GT-R) the ecu works fine, (tested in another GT-R) the wiring from the relay earth to the ecu is fine as I tested continuity and it's good. I suppose the next thing to check is the ecu's earth? I have no codes. Could my attesa hydraulic line pressure sensor just be stuck?

[Samuel Leonard]

i'll just keep updating in the hope that someone in the know will help

i checked the earth wires going to the attesa ecu and they're all ok. i grounded the 4WD pump relay control circuit from the plug on the ecu and the relay closed so the ecu is simply not instructing the pump to run. however, as stated my ecu worked fine in a mates car so the problem must be with the hydraulic line pressure sensor. the ecu must not think it needs to run the pump as it must see adequate line pressure from a faulty sensor. i will rule this out next. anyone with any ideas please let me know!

[Samuel Leonard]

finally i think i've found the problem and it explains everything. my ecu is not ever running the pump because the ecu is getting a constant reading of full line pressure from hydraulic line pressure sensor. it is impossible to diagnose because the workshop manual asks to check pin 42 on the loom that goes into the ecu for continuity to ground. i didn't have continuity to ground. so i decided to plug the ecu back in and back probe this terminal with it all plugged in. i had 5 volts at this terminal which i then grounded and my ecu finally earthed the pump relay control circuit!

in summary, if your 4wd isn't working and you have no codes, back probe terminal 42 on the attesa ecu and see if you have voltage. if you do, try grounding that terminal and see if your pump runs (or at least the relay tries to command the pump to run) as the pump is probably siezed from sitting there stationary for years like mine is.

i now know that a hydraulic assembly should fix my problem as a new pump assembly comes with the pressure sensor and accumulator and valves etc. as one unit.

[DVS JEZ]

Good work