Sub tank fault on 04 TD42

[the evil twin]

If you try Rodneys test and there is no power or it works on Chassis earth but not on the loom earth...

The Sub tank gauge wiring and also the main tank "not full" switch for the Sub Tank Computer all go thru plug B125.

The rest of the main tank wiring all goes thru B123 so it would make sense for a wiring issue (water or damage) in the loom at/from B125 to trip the fail lamp and also for the gauge to cease but for the main to keep working OK.

I can't for the life of me remember exactly where that plug is but from what I see in the Manual it is is pretty low down on the chasis/firewall.

[Yendor]

That would be the connectors on the LHS chassis rail directly under the passengers front seat.

[the evil twin]

Hiya Rodney, knew you would be on the money... for the bonus point, what colour is the middle one (just jokin').

Been a long while since I went looking for them.

Just raised my suspicions when the OP mentioned "bog holes" and has confirmed that his sender is in one piece

[Yendor]

I still think it's an open circuit. But seeing has he's checked the fuel sender unit and earths maybe it is a badly corroded plug.

I will be able to post the wiring diagram up later once I get home. Then I can tell exactly which wire it is in those connectors and the colour of the middle one for you

But if he has a voltage reading or the gauge moves when the wire is earthed then all this is pointless anyway.

[the evil twin]

Agree... open cct will send gauge low and set the fault in the Sub Tank 'poota

Those "B" plugs will be handy only if it is a fault in the loom.
Every time but one the faults I have found have been in the Main or Sub Senders (float fell off, worn or open wipers, broken wire etc) or the plugs at the Sender

[Phat Patroller]

I have found and rectified the issue. It was indeed a broken wire in the sub tank level circuit, but the bog hole threw me off I thought I'd be looking for water ingress or corroded plugs too, but it turns out that was a red herring...

Where the loom ducks back up into the cab, through grommet under passengers seat, I must have caught a branch and it pulled the loom out cutting the sub fuel gauge sender wire and damaging some others.

Solder, heat shrink, tape and some split tubing later and I'm all good again.

Thank you to everyone for your quick resoponses and ideas to put me on the right track.....champions the lot of ya!

[Cuppa]

This thread is a great example of the usefulness of forums. Excellent stuff folks. And Phat .... thanks for feeding back the good results.

[Phat Patroller]

I agree and is exactly the reason I choose to become a member :-)

[peterbr1]

I cant quite remember but I think you may need and extra earth wire some where near the subtank to the body of the car

[4bye4]

I cant quite remember but I think you may need and extra earth wire some where near the subtank to the body of the car

You can never have enough earths on a GU. Yes bad earth can cause subtank pump or guage issues.