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I just bought a 2010 Fiat Ducato Maxi Multijet 120 manual transmission. On the way home going up the mountain when I would shift gears the engine oil pressure warning light would momentarily go on then go off. When I got up to Jerusalem and was driving around the parking lot looking to park the light came on again and said to pull over and shut down the engine immediately. I parked, went to an appointment came back and drove it the rest of the way home without the light coming on. Called the seller who spoke with his driver who said it's been doing this for years. Oil is full with no noticeable leaks, and the records for the vehicle indicate oil and filter changes every 10,000 kilometers over the past few years. I'm only able to connect to the EOBD interface and no DTC's show, although the engine warning light is on.

So this could be a defective oil pressure sensor, wiring or gunk intermittently clogging the oil pick up in the sump?

Wondering what angle to attack this from. Maybe some seafoam to flush the crankcase + oil and filter change then if that doesn't work change the sensor?

The whole thing of the light coming on when shifting gears on an incline has me scratching my head a bit...

Edit

So I was finally able to get my launch to connect and there was a P0520 code; Engine Oil Pressure Sensor/Switch Circuit Malfunction, which means I'll be wiggling some wiring harnesses around tomorrow trying to reproduce the code.

Postscript

So I changed the oil + filter and added about 100ml IPA and about 300ml Napthalene to the crankcase and drove for about 1000 kilometers. Then changed oil + filter again and drove another few hundred kilometers and the problem seems to have gone away.

There is one other thing I did also; I lowered the drivers seat so I could reach the clutch pedal better. The previous driver was allot taller than me and I think my foot might have been slipping on the clutch when I changed gears sometimes...

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  • It seems to me the oil might not be returning to the pan quick enough, so after a bit of harder running, when you release the clutch and the RPMs drop, the oil pressure drops to the point where the sensor isn't seeing enough pressure and the light comes on. A Seafoam treatment in the crankcase may help. If it doesn't, I can think of a few things which might be at cause for this, like a loose pickup tube, bent pickup tube, clogged oil passages, too much flash in the head castings, weak oil pump pressure spring, etc.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Aug 5, 2020 at 22:16
  • @Pᴀᴜʟsᴛᴇʀ2 I'm going to do some testing this morning of the sensor and wiring, but I think it might be something along the lines of what you're saying. The engine has 418k kilometers on it, so I bet it's overdue for a flush... Don't have seafoam here, so I'm going to change the oil + filter and throw in about 150ml of naptha, drive it a few hundred kilometers then change the oil + filter again... See if that helps.
    – Robert S. Barnes
    Commented Aug 6, 2020 at 6:42

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It seems to me the oil might not be returning to the pan quick enough, so after a bit of harder running, when you release the clutch and the RPMs drop, the oil pressure drops to the point where the sensor isn't seeing enough pressure and the light comes on. A Seafoam treatment in the crankcase may help. If it doesn't, I can think of a few things which might be at cause for this, like a loose pickup tube, bent pickup tube, clogged oil passages, too much flash in the head castings, weak oil pump pressure spring, etc.

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It could be any or a combination of all of those, so flushing, cleaning, new (quality or oem) filter etc is a good point to start.

I would make, or purchase, a tee and fit a pressure gauge temporarily to monitor the behavior. Any real pressure loss compared to light action should be obvious.

I would suspect a chafed wire somewhere which brings the light on. Good luck finding that. I would isolate the original wire at both ends (and middle check the wiring diagram) and run a temporary wire to test.

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