Sub Tank Switch

[BryceKernahan]

Hey guys, hoping to get some help with my sub tank switch. (2008 series 4 GU ST 3.0)

I had the dash apart to install some cable for aux power running to the back of the car and installed a new uhf and gone to put everything back together and the sub tank switch has stopped working.
Does the sub tank switch light on the actual switch and the light in the dash only come on when there is fuel in the sub tank or should these LED's illuminate when you press the button even when the tank is empty?
I've considered replacing the switch but Nissan want over $100 for it. Narva do an OE style switch Ive considered replacing it with but the original has 6 wires and the Narva one only 4 wires. Can't seem to find a wiring diagram for the switch so I can identify what the wires are. Ive already had the ground cable disconnected, checked all fuses. there is 12V supply right to the switch, but when you press the button, no lights come on and nothing happens.

any guidance would be appreciated. thanks.

[mudski]

Have you checked to see if fuel is actually pumping into the filler neck?

[Cremulator]

I don't think the switch will work if the main tank is full and if the sub tank is either full or empty.
As long as there is some fuel in both tanks the switch light should come on when you press in the switch.

[BryceKernahan]

hey mate yeah it still transfers fuel upon start up.

[BryceKernahan]

i think i read somewhere on here yesterday that the switch will only work if the sub tank has fuel in it and the main is down by at least 25%..
i think im going forget the aftermarket narva switch and just put a genuine nissan one back in.

[0-TJ-0]

Re-check everthing mate. Make sure your sub tank has plenty of fuel in it and your main is down at least the 25%. Nothing will happen if the conditions aren't met.

Can you borrow someone else's switch before you spend the money?

[pj101]

Hey mate,
I have no idea why, but mine goes out every now and again. When the light shows on the dash, I disconnect the battery, wait a couple of minutes, re-connect and everything is back up and operational.

[Sprock]

Could be unrelated but a while ago a stick ripped the wires off my sub tank - I fixed it all up properly but it still wouldn’t work - many phone calls & investigations on here later & I ended up disconnecting the battery for half an hr then reconnected it & wala it worked .

[the evil twin]

The sub tank fault circuit is a latching circuit IE if it detects an issue and faults out it will not reset even if you fix the fault.
You can only reset the latch by either disco battery, pull the fuse, disco the sub tank computer.

If it faults out you can read the fault code (directions are in the manual) to see what is wrong or what it thinks is wrong.

Hard faults are obviously easy to find, usually a failed pump or tank unit (sub or main).
In intermittent faults poor earthing of the sub is prob 2/3rds of the cause.