oil light

Sounds like you have a dry joint in your instrument panel. Pull the panel out and using a magnifying glass check the solder joints on the instruments that don't work, if two of the gauges are faulty it will most likely be the return path, use the magnifying glass to look for a crack in the solder.

It could possibly be the bracket on the oil pick up broken. Holden has a modified one with a stronger tag for the locking bolt. Do a Google for the Jackaroo forum It comes up as a fairly common fault. My jackaroo did 200000kms but that fault didn't arise.

The website that may help is Australia4wd.com and look in the section Jackaroo technical 4JX1 3.0 TDI

Hi Bazza,
If the oil pressure has been tested and is within specification there is obviously nothing wrong with the oil pump.
Therefore there is no point in changing to a higher viscosity (thicker) oil.

Have you changed the oil filter recently?
Some oil filters do not have anti drain valves in them and all the oil can drain back into the sump over a period of a day or so.

If the oil light and pressure gauge respond in 15-20 seconds I don't think you have a problem worth worrying about.
Just do not rev the motor or drive off till all the lights go out.

Otherwise there are two likely suspects, oil pressure sender, which you have tried, or a fault in the oil pressure gauge and/or the warning lamp electrical connections.
As a previous reply suggests try looking for a 'dry' electrical connection on those two instruments or even a faulty eatrh connection somewhere in the system.
Unfortunately poor earth connections can be a right pain in the proverbial to track down. A test light may help.

Good Luck

Disco.
(who's LandRover does exactly the same thing)