Instrument Panel, Gauges and Warning Indicators: Description and Operation
Instrument Panel Cluster (IPC) Description and OperationThe powertrain control module (PCM) sends serial data to the body control module (BCM) along the primary serial data bus circuit. Serial data is then sent to the instrument cluster along the secondary serial data bus circuit.
The following data is read by the instrument cluster, which then indicates the status as appropriate on the multifunction display (MFD) and/or cluster warning indicators:
- Oil pressure
- High temperature
- Check engine (powertrain)
A powertrain interface module (PIM) is required to convert the serial data generated by the (PCM) into serial data that is compatible with the BCM.
Engine Coolant Temperature Gauge
The instrument cluster receives engine coolant temperature information from the powertrain control module (PCM) via the serial data bus normal mode message. The PCM receives engine coolant temperature information from the engine coolant temperature (ECT) Sensor. The ECT Sensor is a thermistor mounted in the engine coolant stream. Low engine coolant temperature produces a high sensor resistance, while high engine coolant temperature causes a low sensor resistance.
Fuel Gauge
The fuel sender unit provides a percentage value to the instrument cluster based on its position relative to the fuel level. The percentage value will vary between 0 percent with no fuel in the tank and 100 percent with a full tank. The instrument cluster drives the fuel gauge pointer to the appropriate position.
PRNDL Display
The IPC displays the selected gear position as determined by the PCM. The IPC receives a message from the PCM indicating the gear position. When the position of the transmission selector is changed, a large icon is displayed on the MFD in conjunction with the PRND321 constant icon at the bottom of the MFD. The square box around the designated gear letter moves according to what gear is selected on the gear selector.
Speedometer
The instrument cluster receives vehicle speed information from the Powertrain Control Module (PCM) via the speedometer signal circuit. The PCM pulses this circuit to ground. The number of pulses varies with tire size. The PCM receives vehicle speed information from the vehicle speed sensor located in the transmission assembly. Voltage is produced by the speed sensor and is fed to the PCM, which filters and shapes the signal. The PCM then counts the number of pulses received in a given time to determine the vehicle speed. Once the PCM has calculated the vehicle speed, it then pulses the speedometer signal circuit to ground. This causes the 12 volts at instrument cluster to be pulled down to less than 0.5 volt. The instrument cluster then determines the vehicle speed and the miles/kilometers travelled from the number of pulses it receives.
Tachometer
The instrument cluster receives the engine speed (RPM) information from the PCM via the tach signal circuit. The PCM pulses the circuit to ground and the instrument cluster counts the number of pulses to determine the speed (RPM) of the engine
Audible Warnings:
Audible Warnings Description and Operation
An audible warning chime is incorporated in the instrument cluster. This feature is used to emphasize the warning conditions in the following table, with the tone and repetition rate of the chime varied to allow different warnings to be identified by sound.
In addition to the warning conditions displayed on the multifunction display (MFD), the audible warning chime will sound when buttons on the trip computer switch assembly are pressed or certain functions are entered. The description and tone of each warning is described in the following table. The frequency of each tone is listed in the following table.