Principles of Operation
PRINCIPLES OF OPERATIONWhen installing a new instrument cluster, it is necessary to upload the module configuration information to the diagnostic tool. Following installation of the instrument cluster, download the module configuration information from the diagnostic tool into the new instrument cluster. The following items are configurable:
- gulf coast countries (GCC) destination
- traction control
- oil life threshold
- oil minder off
- powertrain control module (PCM) oil life used
- engine idle hour meter
- back up aid
- air suspension
The standard and optional instrument clusters are configurable, hybrid electronic clusters (HEC) that contain a microprocessor, gauges, indicator lamps, and internal circuitry. The instrument cluster uses hardwired circuitry, the standard corporate protocol (SCP), and the controller area network (CAN) to transmit and receive data from other modules. It is very important to understand:
- where the input originates.
- all the information necessary in order for a feature to operate.
- which module(s) receive(s) the input or command message.
- whether the module which received the input controls the output of the feature, or whether it outputs a message over the CAN or SCP communication networks circuits to another module.
- which module controls the output of the feature.
The instrument cluster carries out a display prove-out to verify that the warning/indicator lamps and monitored systems are operating correctly. The safety belt warning indicator illuminates for 65 seconds ±1 second or until the safety belt is fastened. When the ignition key is turned to the ON position, the charging system warning indicator, the low oil pressure warning indicator, and the malfunction indicator lamp (MIL) illuminate until the engine is started and operating normally. Each time the ignition key is turned from the OFF to the ON positions, the following instrument cluster warning indicators prove out for 3 seconds:
- air bag (6 seconds on, 2 seconds off)
- ABS
- BRAKE
- low fuel (if equipped)
- air suspension (5 seconds) (if equipped)
- fire suppression (5 seconds) (police only)
- traction control
- engine coolant over temperature
- powertrain malfunction (wrench)
- traction control active (if equipped)
Gauges
Fuel Gauge
The fuel gauge informs the driver of the amount of fuel remaining in the tank. The instrument cluster is hardwired to the fuel pump sender, which is a variable resistor controlled by the action of a float arm. If the fuel level is high, the resistance in the fuel pump gauge sender will be high, causing the gauge to indicate full (F). When the fuel level is low, the resistance in the fuel pump gauge sender is low, and the gauge indicates empty (E).
Engine Coolant Temperature Gauge
The PCM receives the engine coolant temperature status through hardwired circuitry from the cylinder head temperature sensor. The instrument cluster receives the engine coolant temperature data from the PCM over the high speed CAN. The instrument cluster monitors the engine coolant temperature data received from the PCM and commands the engine coolant temperature gauge pointer.
Tachometer
The tachometer is electrically operated and indicates the engine speed in revolutions per minute (rpm). The tachometer range is 0 to 7,000 rpm. The PCM uses the crankshaft position sensor to measure the engine rpm and sends the data to the instrument cluster, over the high speed CAN, to command the tachometer gauge. If the rpm information sent to the instrument cluster is invalid or missing, the instrument cluster defaults the tachometer to 0 rpm.
Speedometer
The instrument cluster receives the vehicle speed sensor (VSS) signal from the anti-lock brake system (ABS) module over the high speed CAN. The instrument cluster monitors the VSS input from the ABS module and commands the speedometer with a corresponding movement of the pointer.
Indicators
Charging System Warning Indicator
The instrument cluster receives the charging system status from the PCM over the communication network. Charging system data is monitored by the instrument cluster and when the charging system voltage is low, illuminates the charging system warning indicator.
BRAKE Warning Indicator
The parking brake switch and the brake fluid level switch (part of the master cylinder) are hardwired to the instrument cluster. The BRAKE warning indicator uses 3 inputs. The first input is provided by the parking brake switch, and when applied, provides a ground signal to the instrument cluster, illuminating the BRAKE warning indicator. The second input is controlled by the brake fluid level switch. When the brake fluid level is low, the brake fluid level switch closes and provides a ground to the instrument cluster to illuminate the BRAKE warning indicator. The third input uses the base brake system. If a base brake system concern occurs, the anti-lock brake system (ABS) module provides a brake signal to the instrument cluster over the high speed CAN, to illuminate the BRAKE warning indicator. If a loss of communication from the ABS module to the instrument cluster occurs, the BRAKE warning indicator illuminates.
Anti-lock Brake System (ABS) Warning Indicator
The ABS warning indicator is used to indicate an ABS concern or deactivation of the ABS. The instrument cluster, upon receipt of the ABS message from the ABS module over the high speed CAN, turns on the ABS warning indicator.
Malfunction Indicator Lamp (MIL)
The MIL informs the driver of a malfunction in the powertrain that affects the vehicle emissions system. The MIL is illuminated when a fault condition is detected by the powertrain control module (PCM) and a diagnostic trouble code (DTC) has been set. The instrument cluster receives the MIL data from the PCM over the high speed CAN.
Low Fuel Warning Indicator (if equipped)
The low fuel warning indicator is controlled by the instrument cluster and uses hardwired fuel level data from the fuel pump gauge sender. When the fuel level drops below approximately 1/8 of a tank, the instrument cluster illuminates the low fuel warning indicator.
Air Bag Warning Indicator
The air bag warning indicator is used to provide a status of the supplemental restraint system. The instrument cluster receives a message from the restraint control module (RCM) over the high speed CAN. If an air bag system concern is detected, a diagnostic trouble code (DTC) is logged and the RCM sends a message to the instrument cluster to illuminate the air bag warning indicator.
Safety Belt Warning Indicator
The safety belt switches are hardwired to the RCM and the RCM monitors the safety belt switch position.The RCM communicates the safety belt information to the LCM over the SCP which is then relayed to the instrument cluster over the SCP network to turn on or off the safety belt warning indicator according to the safety belt switch position.
Low Oil Pressure Warning Indicator
The instrument cluster is hardwired to the oil pressure switch. The oil pressure switch unit consists of a diaphragm and contact points, which are normally open. When there is low or no oil pressure, the oil pressure switch remains open, removing the ground to the instrument cluster. When sufficient oil pressure exists, the oil pressure switch closes, providing a ground signal to the instrument cluster to turn the indicator on or off according to the engine oil pressure.
Door/Trunk Ajar Indicator
The door ajar switches are hardwired to the driver door module (DDM). When any door is open and the ignition key is in the RUN position, the DDM sends the instrument cluster a message over the SCP communication network to illuminate the door/trunk ajar warning indicator.
Turn Signal Indicators
When the multifunction switch is in the LH turn signal position or the RH turn signal position, voltage is sent from the multifunction switch to the instrument cluster through hardwired circuitry. The instrument cluster flashes the LH or RH turn signal indicators on and off.
High Beam Indicator
When the high beams are turned on, the LCM sends a signal to the instrument cluster over the standard corporate protocol (SCP) communication network to illuminate the high beam indicator.
Speed Control Indicator
The instrument cluster receives the speed control data from the PCM over the high speed CAN. When the speed control is engaged, the PCM provides a signal to the instrument cluster to illuminate the speed control indicator.
Powertrain Malfunction (Wrench) Warning Indicator
The PCM monitors the electronic throttle control and the transmission system and provides the instrument cluster with the operating status over the CAN. When a system concern is detected, the PCM provides the instrument cluster with a signal commanding the instrument cluster to illuminate the powertrain malfunction (wrench) warning indicator.
Check Fuel Cap Warning Indicator
The check fuel cap indicator is used to indicate significant leaks in the fuel tank evaporative emission system due to a loose fuel cap or other fuel evaporative emission system concern. The fuel tank pressure is monitored by the PCM and, once a leak is detected, the PCM signals a fault to the instrument cluster over the high speed CAN.
O/D OFF Indicator
The instrument cluster receives the overdrive off signal from the PCM over the high speed CAN. The overdrive off switch is hardwired to the PCM. When the transmission overdrive is turned off, the overdrive off switch provides a voltage signal to the PCM. The PCM, upon receipt of the overdrive off input signal, provides an overdrive off signal to the instrument cluster and the instrument cluster turns on the O/D OFF indicator.
Engine Coolant Over Temperature Warning Indicator
The PCM receives the engine coolant temperature status through hardwired circuitry to the cylinder head temperature sensor. The instrument cluster receives the engine coolant temperature data from the PCM over the CAN. The instrument cluster monitors the engine coolant temperature data received from the PCM and when the engine coolant temperature is high, or if the vehicle has entered a failsafe cooling mode, the engine over temperature warning indicator illuminates.
Traction Control Indicator
The traction control indicator informs the driver that a traction control event is taking place, by flashing the traction control indicator during the event. The traction control indicator illuminates constantly when a malfunction is detected in the traction control system, or if the traction control system is disabled by the operator. The traction control is controlled by the ABS module over the CAN.
Air Suspension Indicator (if equipped)
The air suspension indicator is hardwired to the instrument cluster. If a air suspension malfunction occurs, the air suspension switch closes to ground, illuminating the air suspension indicator. The air suspension indicator also is illuminated with ignition key in the RUN position and if the air suspension service switch is off.
Fire Suppression Indicator (Police)
If the fire suppression module (FSM) detects a problem with any of the fire suppression system components, the fire suppression indicator will illuminate and a diagnostic trouble code (DTC) is logged.
Engine Idle Hour Meter (Police)
The instrument cluster receives the digital transmission range (TR) sensor status message from the PCM over the high speed CAN, and if the engine speed is greater than 400 rpm, it records the amount of time the engine runs with the transmission in PARK or NEUTRAL.