Keep in mind that we do NOT have a true oil pressure sensor. Our sensor either reads pressure or it doesn't, the needle movement is simulated based upon the RPM that resulted in the oil pressure switch finding over 5 psi (approx), the threshold for turning on the check engine light.
This may be an issue with the cluster itself or a bad pressure switch. I would suggest connecting an OBDII scanner and see what the PCM is actually reporting to narrow it down. If the scanner sees pressure and the needle is at 0, you have a bad instrument cluster. If it momentarily shows 0 psi, you may have a bad switch.....but this should also cause 'Low Oil Pressure' to display in the DIC (if equipped) and/or the oil can light on the dash to illuminate. - You didn't mention either, so I'm thinking a bad cluster.
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