Grand Cherokee 2WD V6-3.7L (2008)
Oil Temperature Gauge: Description and Operation
The oil temperature indicator gives an indication to the vehicle operator of the engine oil temperature. This indicator is controlled by the instrument
cluster logic circuit based upon cluster programming, an input from the upper instrument panel switch pod, and electronic messages received by the
cluster from the Powertrain Control Module (PCM) over the Controller Area Network (CAN) data bus.
The oil temperature indicator function of the reconfigurable dot matrix Organic Light Emitting Diode (OLED) display unit is completely controlled by
the instrument cluster logic circuit, and that logic will only allow this indicator to operate when the instrument cluster receives a battery current input on
the fused ignition switch output (run-start) circuit. Therefore, the OLED oil temperature indication will always be OFF when the ignition switch is in any
position except ON or START. The instrument cluster will turn ON the oil temperature indicator for the following reasons:
Oil Temperature Indicator Request - Each time the cluster is in the compass/trip computer mode and receives a request from the STEP button
on the steering wheel to step to the appropriate sequence of the trip computer display, the oil temperature indicator will be displayed showing the
current engine oil temperature value. The cluster receives electronic engine oil temperature messages from the PCM indicating the temperature.
The indicator remains illuminated until the cluster receives another request from the STEP button, until the cluster arbitrator logic determines that
another display request has priority, or until the ignition switch is turned to the OFF position, whichever occurs first.
The PCM continually monitors the engine oil temperature sensor to determine the engine oil temperature. The PCM then sends the proper electronic
messages to the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN).
For proper diagnosis of the engine oil temperature sensor, the PCM, the EMIC, the CAN data bus or the electronic communication related to oil
temperature indicator operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.