The oil pressure sensor operates as a switch, at a fairly low pressure compared to normal oil pressure with the engine running. The warning light on the instrument panel should turn on with ignition before start, and turn off as soon as the engine is on. There is no other indication of a failed sensor. Even a flickering oil light while driving is an indication of dangerously low oil pressure, and imminent engine damage if continuing to drive. Low oil pressure can be the result of low oil level, and on some cars a seriously sludged engine, blocked oil pickup screen, or damaged oil pump.
It is located on the back of the engine block, with a single wire connecting it to the instrument panel. Leaks from the sensor can be hard to distinguish from leaks at the oil filler tube o-ring seals, or the valve cover. The sensor is similar to the oil drain plug, with aluminum gasket. The same sensor was used on the C900, NG900, 9k, and 9-3 model from 1985-2002.
Oil Pressures Table
The oil pressure switch is closed (low impedance to chassis ground) with engine off, or at oil pressure below about 6 psi. It is open (high impedance to chassis ground) with engine running, and oil pressure above 6 psi.
A test lead with an alligator clip can be attached to the wire connector from the LH (driver) side of the engine. The voltage should be low (near zero) with engine off, and high (close to the battery voltage) with engine on.
- P/N: 9112459
Removing the oil filler tube will create more space to access the pressure sensor. It is attached using 2 10mm bolts at the valve cover and a 12mm bolt to the engine block. The oil filler tube can then be pulled from the sump. Without interference from the oil filler tube the sensor can be removed using a 24mm or 15/16" deep socket. Replacement sensors may vary in size.