Or, as we like to call it here at the brick-yard the "Buzzer Of Doom!"

What it's meant to do.

Function as a normal oil pressure warning light.

Warn you when the oil pressure is below .3 bar and the engine is above 2000 rpm.

So, what's meant to happen is you turn the ignition on, the light glows to indicate there is no oil pressure. You start the engine, it generates oil pressure and when the predetermined pressure has been exceeded then the warning light will extinguish. No buzzer! this is the normal operation of an oil warning light.

If, for example your traveling down the motorway and your oil pressure drops below .3 bar and the engine is above 2000 rpm then the oil light will come on and the buzzer of doom will scare you to death.

Right, that's normal but sometimes the buzzer of doom sounds when it shouldn't, some times sporadic, sometimes it comes on below 2000 rpm, or sometimes it just comes on for a laugh.

So, what should you do?
first of all don't take it for granted that there's a fault with the DOP system, if the buzzer comes on check your oil level. Get your oil pressure checked, spec below.

All engines except JX 1.6TD.
At least 2 bar pressure at 2000 rpm with the oil temperature at 80°c

JX 1.6TD at least 1 bar pressure at 2000 rpm with the oil temperature at 80°c

So, once you've checked that out and your convinced that there is no oil pressure problem what should you do, well you could replace the oil pressure switches. There are 2 switches, one is a conventional oil pressure switch, working in the normal manner, this is a normally closed type switch meaning that at rest (no pressure) the contacts are closed.
There is the second switch which operates the DOP side of things, don't get me wrong, they both work in conjunction with each other but the second switch is what tells the DOP system that the pressure has dropped below .3 bar. This switch is normally open.
The switches are relatively cheap at around 10(GBP 2004)

Or you could have an electrical fault, generally these occur at the connection of the wiring loom and the instrument binnacle, these can be given a quick spruce up with a scotch pad (or the green bit of your washing up sponge!)

The DOP control unit is buried inside your speedometer, with all the associated wiring running forward to it, this includes a speed signal from the engine seeing as though it needs to know if the engine is above or below 2000 rpm.

Testing.

Ignition on, the oil warning lamp should be on. Disconnect low pressure switch, the oil light should go out.

Engine running, engine speed above 2000 rpm

How do I shut it up? my pressure is okay.

There are a couple of ways to do this, the easiest involves simply unplugging a wire, this method only works on vehicles WITHOUT a rev counter.
Diesel, remove the wire from the back of the alternator marked W, this is where the DOP controller gets its engine speed signal from.
Petrol, Next to the ignition coil there should be a green wire with a connector in it, simply unplug this.
What this method does it to confuse the controller that engine isn't running, so in theory the buzzer shouldn't work.

The second method involves making a little jumper lead, securing one end to a good earth and fitting a male spade connector to the other end and unplugging the wire from the .5bar sender unit, this is the unit with a yellow wire going to it. And connecting yellow wire via your jumper lead to earth.
Diesels, dead easy, the sender you want is within easy reach with the hatch lifted to the back of the cylinder head (the foremost face)
Petrol's is slightly more involved seeing as the oil pressure switches are buried and no one can be bothered to replace them when required because they can't easily get to them, that's probably why you are in this pickle in the first place! anyway, if you look from the rear of the van into the engine bay then in the front left corner of the engine bay you will see 2 wires going from the body to the engine with a connector half way down, these are the oil pressure switch wires, again make a jump lead to connect the yellow wire to earth and another to keep the other wire connected. Then go and revel in your now silent cab!

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