Cherokee 4WD L6-4.0L VIN S (1998)
Oil Pressure Warning Lamp/Indicator: Description and Operation
SYSTEM OPERATION
The low oil pressure warning lamp gives an indication when the engine oil pressure is low. The lamp is turned on by the instrument cluster
circuitry for about three seconds after the ignition switch is turned to the On position as a bulb test. After the bulb test, the lamp is controlled by
the instrument cluster circuitry based upon an engine oil pressure message received from the Powertrain Control Module (PCM) on the Chrysler
Collision Detection (CCD) data bus.
The PCM uses an input from the engine oil pressure sensor and internal programming to decide what engine oil pressure message is required. The
PCM then sends the proper message to the instrument cluster on the CCD data bus. If the PCM message indicates that oil pressure is low, the
instrument cluster circuitry turns on the low oil pressure warning lamp.
The engine oil pressure sensor is installed in a threaded hole that penetrates an oil passage of the engine. The engine oil pressure sensor contains a
flexible diaphragm and a variable resistor coil. The diaphragm moves in response to changes in the engine oil pressure, which changes the internal
electrical resistance of the sensor.
