E30 Zone

Good afternoon all,

After many years my M54 swap is nearing completion. I have been finishing off a few bits and pieces and trying to get all the check lights in the panel above the rear view mirror to work/go out.

The only one which is proving difficult is the oil level light. I have traced the wires from the check panel (pins 16 and 20) to the C101 connector. As far as I can see I just need to connect these to the oil level sensor, along with the earth and it should work, which I have done, but it doesn't. I have tried swpping the wires around but the light refuses to go out.

It could be a dodgy sensor, so is there a way to test the wiring? I would have thought that shorting one of the wires to earth would complete the circuit and make the light go out, but this is not the case. So at the moment I am stuck with the oil light on. Any ideas on how to reslove this?

There is oil in the engine, just in case you are wondering...

I'm thinking this could be a resistance thing. The M54 (M50) oil level sensor is not providing the resistance the check control is looking for.

But first I'd probably check the one you have and put a meter across the terminals resistance and voltage full and empty. (you might have to drain the oil)

Hats off for getting this far

E30 Oil level sensor wiring goes via the active check control unit before it gets to the instrument cluster, pretty sure the oil light is only wired to the pressure switch .

fixedwheelnut wrote: ↑

Mon Apr 24, 2023 11:17 pm

E30 Oil level sensor wiring goes via the active check control unit before it gets to the instrument cluster, pretty sure the oil light is only wired to the pressure switch .

Yeah the light on the dash is pressure, the light on the check control is level.

From that diagram it looks like it is measuring resistance as opposed to a float switch, which is my guess.

To check how it works I would measure what the resistance is with/without oil. If you get a change in resistance as opposed to a break in continuity then you know how it works. I would then get a suitable variable resistance pot, put it in series, then in parallel to see if I could put the light out. (or get someone with an m20 to measure the resistance on the sensor when they change the oil - unfortunately my 323i does not have oil level so I can't do it )

Other thing to think about is some cars around the e46 era could have an oil level display, therefore a variable output sensor. This might not be compatible with the E30 which is looking for an on-off or different resistance value.

Thanks for all the information, I will have a look at this. I am not sure if I am using the sensor which came with the E46 or with the E34 sump as it was so long ago! I will investigate.

Passed the MOT yesterday and have driven over 100 miles so far. The only issue I have is when driving up a steepish hill I seem to have a loss of power. I think it may be the fuel pump as it still has the old (pre-engine swap) pump.

You need the mechanical level switch, electronic one wont work

Ah ok, thanks Dan.

I don't suppose you know the part number do you?

Cheers

If you search for E34 M50 oil level sensor you should find the exact one

Ok, thanks.