Oil Pressure Warning Lamp/Indicator: Description and Operation

LOW OIL PRESSURE INDICATOR
A low engine oil pressure warning lamp is used only in the low-line instrument clusters. The low engine oil pressure warning lamp is located on the right side of the instrument cluster overlay, above the engine coolant temperature warning lamp. The low engine oil pressure warning lamp consists of a red lens behind a round cutout in the instrument cluster overlay. An International Control and Display Symbol icon for "Engine Oil" is imprinted in black near the center of the red lens. The icon is clearly visible on the face of the instrument cluster when the lamp is not illuminated, and is silhouetted in a bright red glow when the low engine oil pressure warning lamp is illuminated from behind by a replaceable incandescent bulb and bulb holder unit located on the instrument cluster electronic circuit board. The low engine oil pressure warning lamp is serviced as a unit with the instrument cluster.

The low engine oil pressure warning lamp gives an indication to the vehicle operator when the engine oil pressure is low. This lamp is controlled by the instrument cluster circuit board based upon the cluster programming and electronic messages received by the cluster from the Powertrain Control Module (PCM) over the Chrysler Collision Detection (CCD) data bus. The low engine oil pressure warning lamp bulb receives battery current on the instrument cluster electronic circuit board through the fused ignition switch output (st-run) circuit whenever the ignition switch is in the ON or Start positions; therefore, the lamp will always be OFF when the ignition switch is in any position except ON or Start. The lamp bulb only illuminates when it is switched to ground by the instrument cluster circuitry. The instrument cluster will turn ON the low engine oil pressure warning lamp for the following reasons:
- Bulb Test - Each time the ignition switch is turned to the ON position the lamp is illuminated for about three seconds.
- Engine Oil Pressure Low Message - Each time the cluster receives a message from the PCM indicating the engine oil pressure is about 0.003 kg/sq.cm or lower (about 6 psi or lower), the lamp will be illuminated. The lamp remains illuminated until the cluster receives a message from the PCM indicating that the engine oil pressure is about 0.004 kg/sq.cm or higher (about 8 psi or higher), or until the ignition switch is turned to the OFF position, whichever occurs first. The cluster will only turn the lamp ON in response to an engine oil pressure low message if the engine speed is 300 rpm or greater.
- Actuator Test - Each time the cluster is put through the actuator test, the lamp will be turned ON and OFF in a prescribed sequence to confirm the functionality of the lamp and the cluster circuitry.

The PCM continually monitors the engine oil pressure sensor to determine the engine oil pressure. The PCM then sends the proper engine oil pressure messages to the instrument cluster. If the low engine oil pressure warning lamp fails to light during the bulb test, replace the bulb with a known good unit. For further diagnosis of the engine oil pressure warning lamp or the instrument cluster circuitry that controls the lamp, (Refer to INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). If the instrument cluster turns ON the lamp after the bulb test, it may indicate that the engine or the engine oiling system requires service. For proper diagnosis of the engine oil pressure sensor, the CCD data bus, or the message inputs that control the low engine oil pressure warning lamp, a DRB III scan tool and the appropriate diagnostic information are required.