False low oil pressure gauge readings and warnings

Last Friday I had a frightening experience on Mines Road outside Livermore CA, 15 miles from nowhere, when my oil pressure gauge reading dropped nearly to zero at idle, and some scary verbal warnings popped up on the TFT display, ordering me to shut down the engine immediately. In the event of actual oil pressure of 10 psi or less this is undoubtedly good advice. However, at 2,000 rpm or better the warnings went away, so I continued on always with a foot on the throttle and attempted to limp out to an area where I could get some cell service and call for help. I did make it out to inhabited San Jose and called for a tow. I should note that there were some anomalies in the gauge readings along the way, with the numbers occasionally going up into the 140 psi range or better at 3,000-4000 rpm, which combined with the 0-10 psi readings were more consistent with an electrical issue than an oil pressure issue.

And so it was. After reviewing some Ferrarichat threads on similar experiences -- there are many more in the 465/550/575 group than in this one -- I decided to check the connector at the oil pressure sender. The Ferrarichat threads inform that two wires to the sender -- one for the gauge and one for the TFT warnings -- are positive and that the body of the sender is ground. Zero voltage to ground sends the gauge to zero, and full voltage pegs the needle. I confirmed this by starting the engine on Saturday morning and observing a reading of 20 psi at idle, then unplugging the connector and observing zero oil pressure. I already had the belly pan off the car -- which should be a clue to troubleshooting Sherlocks -- so in my case this was an easy exercise. I then sprayed the contacts with some contact cleaner (female slots on the sender, three pins on the connector) and plugged the connector back together. Gauge readings have now returned to normal.

My theory of the failure is that driving with the belly pan removed had exposed the connector to under-car airflow, which in combination with the bumpy surface of Mines Road had loosened the connector to the point where insufficient power was making it through to ground. The connector sticks straight down from the engine, and in the absence of the belly pan it's definitely in the breeze. This theory is consistent with the occasional readings of a safe 130-140 psi that I had observed; that from time to time a good connection was restored.

I'm sharing this to add to the knowledge base, to advise that the scary warnings my car was throwing at me need not always be an indication of total failure of the oiling system. I would never advise anyone to drive any distance -- not even 100 yards -- with zero psi on the oil pressure gauge. But it need not be a catastrophe either.