Sunfire L4-138 2.3L DOHC VIN D MFI (1995)
Oil Pressure Switch (For Fuel Pump): Description and Operation
DESCRIPTION
The fuel pump and engine oil pressure indicator switch has two functions. One is to indicate low engine oil pressure and the other is to supply
battery voltage to the fuel pump in the event the fuel pump relay fails.
OPERATION
Powering the Fuel Pump
The oil pressure portion of the switch has normally closed contacts. The contacts on the oil pressure switch will open when oil pressure exceeds
41.37 kPa (6 psi). The contacts will close on a decreasing pressure of 13.79 (2 psi). When the contacts are closed, the oil pressure switch sends a
signal to the PCM. The PCM then sends this signal to the PC and the oil pressure telltale lamp on the IPC will illuminate.
The fuel pump portion of the switch has normally open contacts that close on an increasing oil pressure of 41.37 kPa (6 psi), and open on a
decreasing pressure of 13.79 kPa (2 psi). In the event the fuel pump relay fails, the battery voltage is supplied to the fuel pump through the closed
contacts from the switch.
Oil Pressure Warning Lamp
The oil pressure switch is connected to the Powertrain Control Module (PCM). If a low oil pressure condition is detected, the PCM will send a
signal to the Instrument Panel Cluster (IPC). The IPC will receive this signal from the PCM and the IPC will then illuminate the warning lamp.
The electronic instrument cluster utilize a "Low Oil Pressure" telltale lamp that indicates engine oil pressure. The purpose of this lamp is to warn
the operator of a potential engine damaging condition. If the warning lamps are illuminated, then a condition is present that may cause engine
damage.
