Dakota 2WD L4-2.5L VIN P (2001)
Oil Pressure Gauge: Description and Operation
An Oil pressure gauge is standard equipment on all instrument clusters. The oil pressure gauge is located in the upper right quadrant of the instrument
cluster, above the fuel gauge. The oil pressure gauge consists of a movable gauge needle or pointer controlled by the instrument cluster circuitry and a
fixed 90 degree scale on the cluster overlay that reads left-to-right from "L" (or Low) to "H" (or High). An International Control and Display Symbol
icon for "Engine Oil" is located on the cluster overlay, in the center of the gauge directly above the hub of the gauge needle. The oil pressure gauge
graphics are white against a black field except for a single red graduation at the low end of the gauge scale, making them clearly visible within the
instrument cluster in daylight. When illuminated from behind by the panel lamps dimmer controlled cluster illumination lighting with the exterior lamps
turned ON, the white graphics appear blue-green and the red graphics appear red. The orange gauge needle is internally illuminated. Gauge illumination
is provided by replaceable incandescent bulb and bulb holder units located on the instrument cluster electronic circuit board. The oil pressure gauge is
serviced as a unit with the instrument cluster.
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:
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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) for These engines 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) for These engines 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) for These engines the gauge needle is moved to the actual pressure position on the gauge scale.
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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) for these engines the gauge needle is moved to the L (Low) 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 low end of the 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) for these
engines or until the ignition switch is turned to the OFF position, whichever occurs first. The cluster will only turn the check gauges indicator lamp
on in response to an engine oil pressure low message if the engine speed message is greater than zero.
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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) for these engines, the gauge needle is moved to the H (High) graduation at the far right end of the gauge scale. The gauge
needle remains at the high end of the scale until the cluster receives a message from the PCM indicating that the engine oil pressure is below about
755 kPa (109.5 psi) for these engines or until the ignition switch is turned to the OFF position, whichever occurs first.
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Message Failure - If the cluster fails to receive an engine oil pressure message, it will hold the gauge needle at the last indication until a new
message is received, or until the ignition switch is turned to the OFF position, whichever occurs first.
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Actuator Test - Each time the cluster is put through the actuator test, the 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
INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). 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 message inputs to the instrument cluster that control the oil pressure gauge, a DRB III scan tool is required. Refer to the
appropriate diagnostic information.
