Gauge Pack - Operation

OPERATION

All gauges receive battery current through the ElectroMechanical Instrument Cluster (EMIC) circuitry only when the ignition switch is in the ON or START positions. With the ignition switch in the OFF position battery current is not supplied to any gauges, and the EMIC circuitry is programmed to move all of the gauge needles back to the low end of their respective scales. Therefore, the gauges do not accurately indicate any vehicle condition unless the ignition switch is in the ON or START positions.

Each of the EMIC gauges contains an electronically controlled stepper motor unit. The EMIC circuitry completely controls the activation and deactivation of these stepper motors to position each gauge needle in the appropriate position based upon cluster programming and electronic messages received over the Controller Area Network (CAN) data bus or the Local Interface Network (LIN) data bus.

The gauges are diagnosed using the instrument cluster self-test Testing and Inspection. Proper testing of the CAN or LIN data bus and the electronic data bus message inputs to the EMIC that control each gauge requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.

ENGINE TEMPERATURE

The engine coolant temperature gauge gives an indication to the vehicle operator of the engine coolant temperature. 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) or Engine Control Module (ECM), over the CAN data bus.

The engine coolant temperature gauge is driven by an electronic stepper motor 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 Temperature Message - Each time the cluster receives an electronic engine temperature message from the PCM/ECM indicating the temperature is between the low end of normal [about 41 °C (105 °F) for gasoline engines, or about 41 °C (105 °F) for diesel engines] and the high end of normal , about 122 °C (252 °F) for gasoline engines, or about 116 °C (240 °F) for diesel engines], the gauge needle is moved to the actual relative temperature position on the gauge scale.
- Engine Temperature Low Message - Each time the cluster receives an electronic engine temperature message from the PCM/ECM indicating the temperature is low [at or below about 40 °C (104 °F) for gasoline engines, or about 27 °C (81 °F) for diesel engines], the gauge needle is held below the graduation on the far left end of the gauge scale. The gauge needle remains below the low end of the gauge scale until the cluster receives a message from the PCM/ECM indicating that the temperature is above the low end of normal, or until the ignition switch is turned to the OFF position, whichever occurs first.
- Engine Temperature High or Critical Message - Each time the cluster receives an electronic engine temperature message from the PCM/ECM indicating the temperature is high [at or above about 122 °C (251 °F) for gasoline engines, or about 116 °C (240 °F) for diesel engines], the gauge needle is moved to the red graduation at the high end of the gauge scale, the engine temperature indicator is illuminated and a single chime tone is sounded. The gauge needle remains at the red graduation and the engine temperature indicator remains illuminated until the cluster receives a message from the PCM/ECM indicating that the temperature is below about 122 °C (251 °F), or until the ignition switch is turned to the OFF position, whichever occurs first. The chime tone feature will only repeat during the same ignition cycle if the engine temperature indicator is cycled OFF and then ON again by the appropriate messages from the PCM/ECM. Should the temperature exceed 125 °C (257 °F) for gasoline engines, 119 °C (246 °F) for diesel engines, the chime will be continuous.
- Communication Error - If the cluster fails to receive an engine temperature message, it will hold the gauge needle at the last indication for about five seconds or until the ignition switch is turned to the OFF position, whichever occurs first. After five seconds, the cluster will move the gauge needle to the low end of the gauge scale.
- Self-Test - Each time the cluster is put through the self-test, the engine coolant temperature 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/ECM continually monitors the engine coolant temperature sensor to determine the engine operating temperature. The PCM/ECM then sends the proper messages to the EMIC. If the instrument cluster turns ON the engine temperature indicator due to a high or critical engine coolant temperature gauge reading, it may indicate that the engine or the engine cooling system requires service.

FUEL

The fuel gauge gives an indication to the vehicle operator of the level of fuel in the fuel tank. This gauge is controlled by the instrument cluster circuit board based upon cluster programming and electronic fuel level messages received by the cluster from the Totally Integrated Power Module (TIPM) over the CAN data bus.

The fuel gauge is driven by an electronic stepper motor 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:

- Fuel Level Message - The TIPM provides a constant current source to the fuel level sending unit and monitors a return input on a fuel level sense circuit. The resistance through the fuel level sending unit increases as the fuel level rises and decreases as the fuel level falls causing changes in the fuel level sense input voltage. The TIPM then sends the appropriate electronic fuel level messages to the cluster. The cluster programming applies an algorithm to calculate the proper fuel gauge needle position based upon the fuel level message input, then moves the gauge needle to the proper relative position on the gauge scale. This algorithm is used to dampen gauge needle movement against the negative effect that fuel sloshing within the fuel tank can have on accurate inputs from the fuel tank sending unit to the TIPM.
- Less Than 11 Percent Tank Full Message - Each time the fuel level message to the cluster indicates the fuel tank is about 11 percent full or less for 10 consecutive seconds and the vehicle speed is zero, or for 60 consecutive seconds and the vehicle speed is greater than zero, the gauge needle is moved to about the one-sixteenth graduation on the gauge scale, the low fuel indicator is illuminated, and a single chime tone is sounded. The low fuel indicator remains illuminated until the fuel level message indicates that the fuel tank is greater than about 14 percent full for 10 consecutive seconds and the vehicle speed is zero, or for 60 consecutive seconds and the vehicle speed is greater than zero, or until the ignition switch is turned to the OFF position, whichever occurs first. The chime tone feature will only repeat during the same ignition cycle if the low fuel indicator is cycled OFF and then ON again by the appropriate messages from the TIPM.
- Less Than Empty Stop Message - Each time the cluster receives a fuel level message indicating the fuel level in the fuel tank is less than the E (or Empty) gauge needle stop position for five consecutive seconds, the gauge needle is moved to the low end of the gauge scale and the low fuel indicator is illuminated immediately. This input would indicate that the fuel level sense input to the TIPM is a short circuit.
- More Than Full Stop Message - Each time the cluster receives a fuel level message indicating the fuel level in the fuel tank is more than the F (or Full) gauge needle stop position for ten consecutive seconds, the gauge needle is moved to the low end of the gauge scale and the low fuel indicator is illuminated immediately. This input would indicate that the fuel level sense input to the TIPM is an open circuit.
- Self-Test - Each time the cluster is put through the self-test, the fuel 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 TIPM continually monitors the fuel tank sending unit to determine the level of fuel in the fuel tank. The TIPM then sends the proper electronic fuel level message to the EMIC and other electronic modules in the vehicle over the CAN data bus. The TIPM will store a Diagnostic Trouble Code (DTC) for any fault detected in the fuel level sense circuit.

SPEEDOMETER

The speedometer gives an indication to the vehicle operator of the vehicle road speed. This gauge is controlled by the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster from the PCM/ECM over the CAN data bus.

The speedometer is driven by an electronic stepper motor 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:

- Vehicle Speed Message - Each time the cluster receives an electronic vehicle speed message from the PCM/ECM it will calculate the correct vehicle speed reading and position the gauge needle at that relative speed position on the gauge scale. The cluster will receive a new message and reposition the gauge pointer accordingly about every 88 milliseconds. The gauge needle will continually be positioned at the relative vehicle speed position on the gauge scale until the vehicle stops moving, or until the ignition switch is turned to the OFF position, whichever occurs first.
- Communication Error - If the cluster fails to receive a speed message, it will hold the gauge needle at the last indication for about three seconds, or until the ignition switch is turned to the OFF position, whichever occurs first. After three seconds, the gauge needle will return to the left end of the gauge scale.
- Self-Test - Each time the cluster is put through the self-test, the speedometer 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/ECM continually monitors the Vehicle Speed Sensor (VSS) to determine the vehicle road speed. The PCM/ECM then sends the proper vehicle speed messages to the EMIC.

TACHOMETER

The tachometer gives an indication to the vehicle operator of the engine speed. This gauge is controlled by the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster from the PCM/ECM, over the CAN data bus.

The tachometer is driven by an electronic stepper motor 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 Speed Message - Each time the cluster receives an electronic engine speed message from the PCM/ECM it will calculate the correct engine speed reading and position the gauge needle at that relative speed position on the gauge scale. The cluster will receive a new message and reposition the gauge pointer accordingly about every 88 milliseconds. The gauge needle will continually be repositioned at the relative engine speed position on the gauge scale until the engine stops running, or until the ignition switch is turned to the OFF position, whichever occurs first.
- Communication Error - If the cluster fails to receive a speed message, it will hold the gauge needle at the last indication for about three seconds, or until the ignition switch is turned to the OFF position, whichever occurs first. After three seconds, the gauge needle will return to the left end of the gauge scale.
- Self-Test - Each time the cluster is put through the self-test, the tachometer 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/ECM continually monitors the Crankshaft Position Sensor (CKP) to determine engine speed. The PCM/ECM then sends the proper engine speed messages to the EMIC.