Oil Pressure Gauge: Operation

WARNING: This page is about a different car, the 2003 Dodge Dakota. However, it is still accessible from the selected car via links, so may be relevant.

The oil pressure gauge gives an indication to the vehicle operator of the engine oil pressure. This gauge is controlled by the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster from the Powertrain Control Module (PCM) over the Programmable Communications Interface (PCI) data bus.

The oil pressure gauge is an air core magnetic unit that receives battery current on the instrument cluster electronic circuit board through the fused ignition switch output (run-start) circuit whenever the ignition switch is in the On or Start positions. The cluster is programmed to move the gauge needle back to the low end of the scale after the ignition switch is turned to the Off position. The instrument cluster circuitry controls the gauge needle position and provides the following features:

Engine Oil Pressure Message -The instrument cluster circuitry restricts the oil pressure gauge needle operation in order to provide readings that are consistent with customer expectations. Each time the cluster receives a message from the PCM indicating the engine oil pressure is between about 6.9 kPa (1 psi) and 137.9 kPa (20 psi), the cluster holds the gauge needle at a point about 11 degrees above the low end of normal increment on the gauge scale. Each time the cluster receives a message from the PCM indicating the engine oil pressure is between about 517.1 kPa (75 psi) and 755 kPa (109.5 psi), the cluster holds the gauge needle at a point about 7.4 degrees below the high end of normal increment on the gauge scale. When the cluster receives messages from the PCM indicating the engine oil pressure is between about 137.9 kPa (20 psi) and 517.1 kPa (75 psi), the gauge needle is moved to the actual relative pressure position on the gauge scale.
Engine Oil Pressure Low Message -Each time the cluster receives a message from the PCM indicating the engine oil pressure is below about 6.9 kPa (1 psi), the gauge needle is moved to the graduation at the far left end of the gauge scale, the check gauges indicator is illuminated, and a single chime tone is generated. The gauge needle remains at the left end of the gauge scale and the check gauges indicator remains illuminated until the cluster receives a message from the PCM indicating that the engine oil pressure is above about 6.9 kPa (1 psi), or until the ignition switch is turned to the Off position, whichever occurs first. The cluster will only turn the check gauges indicator on in response to an engine oil pressure low message if the engine speed message is greater than zero.
Engine Oil Pressure High Message -Each time the cluster receives a message from the PCM indicating the engine oil pressure is above about 755 kPa (109.5 psi), the gauge needle is moved to the graduation at the far right end of the gauge scale. The gauge needle remains at the right end of the gauge scale until the cluster receives a message from the PCM indicating that the engine oil pressure is below about 755 kPa (109.5 psi), or until the ignition switch is turned to the Off position, whichever occurs first.
Communication Error -If the cluster fails to receive an engine oil pressure message, it will hold the gauge needle at the last indication about forty seconds or until the ignition switch is turned to the Off position, whichever occurs first. After forty seconds, the cluster will move the gauge needle to the left end of the gauge scale.
Actuator Test -Each time the cluster is put through the actuator test, the oil pressure gauge needle will be swept to several calibration points on the gauge scale in a prescribed sequence in order to confirm the functionality of the gauge and the cluster control 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. For further diagnosis of the oil pressure gauge or the instrument cluster circuitry that controls the gauge, (Refer to DIAGNOSIS AND TESTING-INSTRUMENT CLUSTER ). If the instrument cluster turns on the check gauges indicator due to a low oil pressure gauge reading, it may indicate that the engine or the engine oiling system requires service. For proper diagnosis of the engine oil pressure sensor, the PCM, the PCI data bus, or the electronic message inputs to the instrument cluster that control the oil pressure gauge, a DRBIII(R) scan tool is required. Refer to the appropriate diagnostic information.