sub tank indication

[cookster]

Hi new to this. just bought a 2003 GU and my sub tank light is always on. Filled both Main & sub tanks. and have used 3/4 of main tank fuel, but sub tank has not moved and light is still on. ANY ideas "Cookster"

[macca86]

Post an intro first. If the sub light stays on that indicates a fault with the sub tank. The sub tank on patrols transfers into main tank rather than fuel the engine. It should transfer a little on start up every time once your main tank is 3/4 to half full

[Yendor]

Try disconnecting the battery for half an hour. If this turns off the light you will need to run an extra earth lead to your chassis.

[Sanpeter]

Just had the same problem. Found elsewhere it could be an earth problem, it could be that the sub tank was overfilled or it could be the sub tank processor.
Anyway the easy answer, which worked for me and lots of others is just disconnect your battery for 5 - 10 mins.
All is working fine now.

[MEGOMONSTER]

Try disconnecting the battery for half an hour. If this turns off the light you will need to run an extra earth lead to your chassis.

Extra earth from subtank to chassis. It seems I have this same problem now.

Light is on button but not transferring.
I have disconnected the battery already. Which I thought fixed it, but then subtank light on dash came up.
So I disconnected again, dash light is off but still not transferring.

But it does give a sprinkle into the main tank everytime I start it.

I can hear the transfer motor werrrrrring but not fill the main tank.

[Winnie]

If you take the fuel cap for the main tank off can you see fuel flowing?

[MEGOMONSTER]

If you take the fuel cap for the main tank off can you see fuel flowing?

Only a trickle on start up. But not by hitting the sub tank button.

[Dananjen]

Hi All, I have a similar issue in my 2002 GUIII,

I have recently fitted new stereo and UHF, prior to fitting these, I had no "subtank dash light" on, but now it is of yet feeding from the main tank. I have tried pushing the button on the dash, and this doesn't turn the dash light off. I haven't touched this side of the wiring, Could it be a faulty button in the dash ??

[boots]

Try removing the fuse first check and replace or put back in. Second disconnect the battery for a while then reconnect to see if the light goes out .

[the evil twin]

Hi everyone... OK... the old "sub tank light" issue once again eh.

First off the warning light has nothing to do with the Sub Tank switch as such IE it will tell you if it is faulty but operating the switch does bugger all if the warning light is illuminated.

Secondly the warning light should latch once there is a fault detected even if the fault goes away.
People have told me that isn't always the case but so far I have always found it to be so (just sayin' is all).

Third, you need to check fuses 24 and 27 (bottom 2 fuses first row) and 28 (bottom fuse second row)

After all that... to reset the system and extinguish the warning light, erase the fault codes and reset the latch you need to disconnect the battery ground or unplug the sub tank control box.

Before you do that it is a good idea to do one of two things
a) run an earth from the sub tank to chassis
OR
b) read the fault codes so you know what it "thinks" is wrong
So if the warning lamp is illuminated.
Turn the ignition off
Turn ignition on
Press the Sub Tank switch On and Off at least 5 times in quick succession
The light should then flash on and off every two seconds (if it doesn't try again quicker or slower)
Once it is flashing wait at least 10 seconds then start the engine, now it gets interesting...
You should see 4 or 5 very quick flashes (this indicates the control unit or computer if you prefer is latched and has codes)
You will then have a long pause (a few seconds) then a long flash ( a few seconds)... get ready
The next flash will be a medium (approx 1/2 second) then 1 or more short flashes if you get another medium flash then more short ones that is a second fault
1 medium and 1 short means the fault is in the main fuel tank full sensor or wiring
1 medium and 2 short - sub fuel tank sender or wiring
1 medium and 3 short - no pump power
1 medium and 4 short - pump wiring

Now, if the fault has disappeared and you reset the warning light then happy days

If you disconnect the battery ground to reset the control box and the warning light illuminates after a short time (other then for ign on bulb test) then it means you still have a fault detected you can either fault find or bite the bullet and fit an extra earth wire between tank and chassis which probably has about an 80% success rate

If you fit the strap, then disconnect the battery ground and the light still illuminates after a short time then you need to sort out fault codes.

Bottom line is this... you can fix the fault or have a fault disappear but until you disconnect the battery the controller will not (or at least should not) extinguish the light which means the sub will self test depending on the fault but will not transfer fuel on demand IE if you look down the tank filler you may see fuel transfer during the test period of a minute or two but you wont see fuel transfer when you press the button

Sorry for the long post but hope that helps at least some people