Incorrect oil pressure; sensor or gauge?

[Cooper99]

The oil pressure gauge in my car shows too low pressure. I have measured with an external gauge and the oil pressure is fine.

What is the most common cause when the gauge shows incorrect oil pressure; the gauge or the sensor?

 

[Per-Anders]

It's most common to be the sender.
I recently had the same issue and the old sender had a small internal leak which made the sender to read incorrect pressure, on idle the pressure was high and it was droping when reving up.

 

[Cooper99]

It's most common to be the sender.
I recently had the same issue and the old sender had a small internal leak which made the sender to read incorrect pressure, on idle the pressure was high and it was droping when reving up.

Thanks. Then I should order a new one.