Sub tank issues

[Not so grey nomad]

I have an issue, my subtank warning light comes on the dash board and I can no longer swithch the sub tank on.
I had it fixed and it lasted about a week. Any thoughts
Thanks

[4bye4]

I had it fixed and it lasted about a week. So what was done to fix it for a week. If it was a loose wire or somthing it might have happned again. Faulty earth perhaps? Not much information to go on mate. Who are you, who fixed it before, how old is the vehicle, when did it first fail etc. would help people make suggestions. Welcome to the forum BTW.

[the evil twin]

Sounds like a dodgy earth to me (most other faults like senders, pump etc are hard IE when they go they go)... either run an aux earth from the tank to chassis in blind hope or read the trouble code from the Sub Tank Poota and see what it thinks is wrong.

If you have already done the earth then reset the Poota (pull the fuses or disco the battery) and see if it faults out again.

[Not so grey nomad]

Thanks guys, I have been the proud owner of my Patrol for 2 weeks dealer fixed under warranty the first time but I have headed of around Oz and am not going to be anywhere near the dealer again. I am waiting for a call back from them to see what they did to fix it the first time. It is a 2012 year with only 77,000 km on it, I am quite mechanical bit what the hell is a Poota. I will try the battery trick and have a look at the earth.
Thanks Guys I will let you know how I go and thanks again for the advice

[the evil twin]

Poota - Official forum abbreviation for "Computer"

The Sub Tank System is controlled by a small "Poota" in the dash ('bout the size of a ciggy packet).
The Poota monitors the fuel levels in the main and sub, wiring, pump and switch and if it detects a fault it illuminates the warning light.
When that happens you have to reset the Poota by removing power even if the fault is fixed and you cannot transfer fuel until you do.
The Sub Tank system runs every time you start the car for 15 seconds or so IF there is fuel in the sub and the main is less than 3/4 full as a "self test".
This means that if you disconnect the battery but haven't actually fixed the fault the light will go out and everything will be OK until the next self test or the intermittent fault occurs again

GU's are notorious for crap earthing (esp for the fuel tank senders, lights and Brake Controllers if towing)... on every GU I owned I ran an extra earth (couple of bucks at Supercheap if you can't make your own) from Battery to Chassis and Chassis to Body.

[the evil twin]

... once you get your head around the idiosyncrasies of Patrols your 2012 with only 77K on it should do several laps of Oz no worries.

May I recommend you purchase a Scangauge OBDII Reader or similar (150 bucks more or less depending).

Brilliant bit of kit and will tell you Turbo boost pressure, coolant temp, fuel useage, true speed plus heaps of others and most importantly read and reset engine fault codes and check engine light

[Not so grey nomad]

I have reset the Poota (I feel like an idiot for asking what that meant) and it canceled the fault on the dash I will look at the earth tomorrow I have a full tank so I cant check if it is working I will definitely invest in a scanguage for a couple of hundred bucks it sound like a must have,
Thanks again for all your great help what a great sight

[Cuppa]

Did you by any chance fill the main tank & whilst doing so try to squeeze in as much as you could, with the sub tank also full? I have found that doing this will cause the sub tank light to remain on every time. Solution is to use some fuel from the main tank, & then disconnect & reconnect the battery. In my case I have already fitted a couple of extra earth cables.

What I have learned to do to avoid the issue to to stop filling when the pump clicks off & to resist the urge to squeeze a bit more in.

[Bigcol]

What I have learned to do to avoid the issue to to stop filling when the pump clicks off & to resist the urge to squeeze a bit more in.

funny you should say this Cuppa,
I always "squeeze" in as much as I can when about to travel........ if I can see the fuel in the filler neck, then she is full...... for both tanks

[Cuppa]

funny you should say this Cuppa,
I always "squeeze" in as much as I can when about to travel........ if I can see the fuel in the filler neck, then she is full...... for both tanks

On occasions when heading into remote country I do that, knowing I'll need to do the battery disconnect at some point to switch off the sub tank light & restore sub tank switch operation. When I first discovered this 'glitch’ I was concerned that I may not be able to rely on the sub tank pump operating when I needed it, so carry a jiggle syphon hose tested in a sub tank to jerry can situation.

[Not so grey nomad]

Hi Cuppa, that is exactly what I did both times it has tripped, since I have reset the putter I have pumped fuel from sub to main several times with out an issue, however I haven't refilled the tank yet I think you have hit the nail on the head. Have you worked out if topping of the main tanks is the issue or topping of the sub tanks that is the issue, if so let me know if not I will try both separately and see if I can work out which one is the issue.
Thanks again all now I feel I know how to prevent it and also how to reset/fix it if it happens.
Cheers

[the evil twin]

You will find that 99.9% of vehicles will not have an issue with the filling tripping a fault.
The ones that do will be because of an issue with the sender (main or sub as the poota monitors both).

IIRC (and I may easily be wrong) an open main tank sender manifests as off scale high.
A fault like that will trip the Sub Tank transfer system and may occur when filling to the brim if the wiper on the sender is out of adjustment/worn