Principles of Operation - Part 1

Principles of Operation - Part 1

The instrument cluster is a configurable, hybrid electronic cluster (HEC) that contain a microprocessor, gauges, indicator lamps, message center, warning chimes and internal circuitry. The instrument cluster uses hardwired circuitry and the controller area network (CAN) to transmit and receive data from other modules. For additional information regarding the communication networks, Information Bus. 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 circuits to another module.
- which module controls the output of the feature.

Instrument Cluster

Instrument Cluster Configuration

When 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 and the vehicle identification number (VIN) from the diagnostic tool into the new instrument cluster. Following installation of the instrument cluster, the instrument cluster and the powertrain control module (PCM) need to be mated.

The following items are configurable:

- odometer unit (English/metric)
- speedometer calibration
- overspeed warning (for service use only at [GCC] countries)
- compass
- outside air temperature
- outside air units
- gallon display
- metric display type
- default language
- default oil life warning threshold
- autolamp delay timer
- auto locks
- reverse mirror
- tire pressure monitoring system
- 4x4 module
- easy entry/exit
- roll stability control (RSC)/interactive vehicle dynamics (IVD)
- power running boards
- transmission control module (TCM)
- back-up/park-aid control
- auto-unlock
- key-in-ignition chime
- A/C clutch

Instrument Cluster Prove-Out

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 60 seconds ±1 second or until the safety belt is fastened. When the ignition switch is turned to the ON position, the charging system warning indicator (base instrument cluster), 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 switch is turned from the OFF to the ON positions, the following instrument cluster warning indicators prove out for 3 seconds:

- engine coolant over temperature warning indicator (base instrument cluster)
- air bag warning indicator (6 seconds)
- BRAKE warning indicator
- tire pressure monitoring system (TPMS) warning indicator
- ABS warning indicator
- check fuel cap (base instrument cluster)
- powertrain malfunction (wrench) warning indicator (base instrument cluster)
- 4x4 LOW indicator (if equipped)
- 4x4 high indicator (if equipped)
- AdvanceTrac with Roll Stability Control (RSC) indicator

Speedometer

The instrument cluster receives the vehicle speed data from the powertrain control module (PCM) over the high speed CAN. The instrument cluster monitors the vehicle speed input and commands the speedometer with a corresponding movement of the pointer.

Odometer

The odometer indicates the vehicle distance traveled whenever the ignition switch is in the RUN position, based upon rolling count data sent from the PCM over the high speed CAN. The instrument cluster provides a reset button to allow the trip odometer to be reset to 0. When the reset button is pressed, the trip odometer is reset. The trip odometer accumulates and registers up to 999.9 kilometers or 999.9 miles.

Engine Coolant Temperature Gauge

The powertrain control module (PCM) receives the engine coolant temperature status through hardwired circuitry to the engine coolant temperature (ECT) sensor (4.0L engine), or from the cylinder head temperature (CHT) sensor (4.6L engine). 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.

Fuel Gauge

The instrument cluster receives the fuel level signal from the fuel level sensor, part of the fuel pump module. The fuel level sensor measures variable resistance in the fuel tank depending on the current fuel level. When the fuel level is low, the resistance in the unit is high (180 ohms ±4 ohms). When the fuel level is high, the resistance in the unit is low (10 ohms ±2 ohms).

The instrument cluster uses 4 different operating modes to calculate the fuel level:

- Anti-slosh (default mode)
- Key OFF fueling
- Key ON fueling
- Recovery

After a fuel fill up, the time for the fuel gauge to move from empty (E) to full (F) ranges from 2 seconds to 55 minutes depending on which operating mode the fuel gauge is in.

The default fuel gauge mode is called the anti-slosh mode. To prevent fuel gauge changes from fuel slosh (gauge instability due to changes in fuel sender readings caused by fuel moving around in the tank), the fuel gauge takes approximately 55 minutes to go from empty (E) to full (F).

The key OFF fueling mode (2 seconds to read empty [E] to full [F]) requires 3 conditions be met:

- The key must be in the OFF position throughout the entire refueling of the vehicle.
- At least 15% of the vehicle's fuel capacity must be added to the fuel tank.
- The instrument cluster must receive a valid key ON fuel sender reading within 1 second of the key being put into the RUN position. The key ON sample readings are considered valid if the fuel sender reading is between 10 ohms ±2 ohms and 180 ohms ±4 ohms.

If these conditions are not met, the fuel gauge stays in the anti-slosh mode, which results in a slow to read full (F) event.

The key ON fueling mode (approximately 90 seconds to read empty [E] to full [F]) requires 3 conditions be met:

- The transmission is in PARK (P).
- The key is in the RUN position.
- At least 15% of the vehicle's fuel capacity must be added to the fuel tank.

In key ON fueling mode, a 30-second timer activates after the transmission is put into the PARK (P) position. When the 30-second time has elapsed and at least 15% of the vehicle's fuel capacity has been added, the fuel gauge response time is 90 seconds to read from empty (E) to full (F). When the transmission is shifted out of PARK (P), the fuel gauge strategy reverts to the anti-slosh mode. The key ON fueling mode prevents slow to read full events from happening if the customer refuels the vehicle with the key in the RUN position.

Recovery mode is incorporated into the instrument cluster strategy to recover from a missing fuel level input after a refueling event. Missing fuel level inputs result from intermittent opens in the fuel sender or its circuits. Recovery mode (empty [E] to full [F] approximately 20 minutes) is initiated when the following 2 conditions are met:

- The instrument cluster is in the anti-slosh (default) mode.
- The actual fuel level in the tank is greater than what is being displayed by the fuel gauge.

Charging System Warning Indicator (base instrument cluster)

When a generator malfunction occurs that prevents the generator from charging the battery, the generator regulator grounds the PCM input to ground. The PCM senses the ground state and sends a communication message over the high speed CAN to the instrument cluster to illuminate charging system warning indicator, which indicates a charging system fault has occurred.

BRAKE Warning Indicator

The parking brake switch is hardwired to the smart junction box (SJB) and the brake fluid level switch is hardwired to the anti-lock brake system (ABS) module. The BRAKE warning indicator uses 2 inputs. The first input is provided by the parking brake switch, and when applied, provides a ground signal to the SJB. The SJB sends the instrument cluster a message over the medium speed CAN to turn on the BRAKE warning indicator. The second input is controlled by the ABS module. The ABS module, upon receipt of a low brake fluid level signal or base brake system concern, provides a brake signal to the instrument cluster over the high speed CAN to illuminate the BRAKE warning indicator.

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 diagnostic trouble code (DTC) is detected by the PCM. The instrument cluster receives the MIL data from the PCM over the high speed CAN.

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 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 RCM monitors the safety belt position through the safety belt buckle switch and communicates the safety belt status to the instrument cluster over the high speed CAN. When the safety belt is buckled, the RCM receives a ground signal and sends a message to the instrument cluster to turn off the safety belt warning indicator. When the safety belt is unbuckled, the ground to the RCM is removed and the RCM sends a message to the instrument cluster to illuminate the safety belt warning indicator.

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 Ajar Indicator

The door ajar indicator informs the driver that one or more doors, the liftgate or the liftglass is open while the ignition switch is in the RUN position. When a door, liftgate, or liftglass is ajar, the SJB sends a message to the instrument cluster over the medium speed CAN to illuminate the door ajar indicator.

Turn Signal Indicators

The SJB sends a message to the instrument cluster over the medium speed CAN when the multifunction switch is in the RH and LH turn position. When the multifunction switch is in the RH or LH turn position, the instrument cluster flashes the RH or LH turn indicators.

High Beam Indicator

When the high beams are turned on, the SJB sends a signal to the instrument cluster over the medium speed CAN 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 (base instrument cluster)

The instrument cluster receives the powertrain status from the PCM over the high speed CAN. When a powertrain system concern is detected, the PCM sends the instrument cluster a command signal to illuminate the powertrain malfunction (wrench) warning indicator. If the 4WD control module detects a failure with the 4WD drive system, the 4WD control module sends a message to the instrument cluster over the CAN to illuminate the powertrain malfunction (wrench) warning indicator. On 4.6L engines, if the transmission control module (TCM) detects a failure with the transmission, the TCM sends a message to the instrument cluster over the CAN to illuminate the powertrain malfunction (wrench) warning indicator.

Tire Pressure Monitoring System (TPMS) Warning Indicator

Each road tire is equipped with a tire pressure sensor fastened to the inside rim of the wheel. The pressure sensor is covered by the tire and is not visible unless the tire is removed. The pressure sensor is located opposite (180 degrees) from the valve stem. The tire-mounted pressure sensors transmit signals to the SJB by using the valve stem as an antenna. These signals are sent approximately every 60 seconds when the vehicle speed exceeds 32 km/h (20 mph). The SJB compares each tire pressure sensor signal against low and high pressure limits. If the SJB determines that the tire pressure has exceeded the limit, the SJB communicates over the medium speed CAN to the instrument cluster, which then illuminates the TPMS warning indicator.

Check Fuel Cap Warning Indicator (base instrument cluster)

The check fuel cap warning 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 (4.0L Engine)

The instrument cluster receives the overdrive off signal from the PCM over the HS-CAN. The overdrive off switch is hardwired to the PCM. When the transmission overdrive is turned off, the overdrive off switch provides a ground signal to the PCM. The PCM, upon receipt of the overdrive off ground signal, provides an overdrive off message to the instrument cluster to turn on the O/D OFF indicator.

O/D OFF Indicator (4.6L Engine)

The instrument cluster receives the overdrive off signal from the transmission control module (TCM) over the high speed CAN. The overdrive off switch is hardwired to the TCM. When the transmission overdrive is turned off, the overdrive off switch provides a ground signal to the TCM. The TCM, upon receipt of the overdrive off ground signal, provides an overdrive off message to the instrument cluster to turn on the O/D OFF indicator.

4x4 High and 4x4 LOW Indicators

The instrument cluster receives the 4x4 high and 4x4 LOW information from the four wheel drive (4WD) control module over the high speed CAN. When either 4x4 high or 4x4 low are selected, the 4WD control module provides a 4x4 status message to the instrument cluster to turn on the appropriate indicator.

Engine Over Temperature Warning Indicator (base instrument cluster)

The PCM receives the engine coolant temperature status through hardwired circuitry from the ECT sensor (4.0L engine), and from the cylinder head temperature (CHT) sensor (4.6L engine). 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 when the engine coolant temperature is high, the engine over temperature warning indicator illuminates.

AdvanceTrac with Roll Stability Control (RSC)

The AdvanceTrac with RSC indicator informs the driver that a traction control event is taking place, by flashing the traction control indicator during the event. The AdvanceTrac with RSC 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 ABS module sends a message to the instrument cluster along the CAN bus to illuminate the traction control/roll stability control indicator. The AdvanceTrac with RSC is controlled by the ABS module over the HS-CAN.

Information And Message Center

The message center electronic functions use both hardwired inputs and the controller area network (CAN) to transmit and receive information.

The message center provides the following features:

- information displays
- setup displays
- system check messages
- warning messages

The message center information can be selected through the TRIP/RESET button (base cluster) and by the INFO, SETUP, and RESET buttons (high series cluster).

Information Displays (Base Instrument Cluster)

The information displays are non-timed modes. The selected mode remains on until the driver presses a message center switch to change the mode, or until it is overridden by another mode. The information display modes are:

- odometer/trip odometer, compass headings
- distance to empty
- average fuel economy
- setup menu

Information Displays (High Series Instrument Cluster)

The information displays are non-timed modes. The selected mode remains on until the driver presses a message center switch to change the mode, or until it is overridden by another mode. The information display modes are:

- odometer/trip odometer, compass headings, outside air temperature display (with dual electronic automatic temperature control)
- distance to empty
- average fuel economy
- instantaneous fuel economy
- fuel used
- trip elapsed drive time
- blank

Setup Displays (Base Instrument Cluster)

The setup displays are timed modes and terminate after a finite interval. Press the TRIP/RESET button to scroll through the SETUP MENU display sequence. If the TRIP/RESET button is not pressed within 4 seconds, the message center returns to the INFO MENU. The setup display modes are:

- AWD lock (vehicles equipped with AdvanceTrac with roll stability control [RSC] only)
- system check
- units (English/metric)
- language
- autolamp
- autolock
- autounlock
- park aid
- oil life start value

Setup Displays (High Series Instrument Cluster)

The setup displays are timed modes and terminate after a finite interval. Press the SETUP button for the following displays:

- AWD lock (vehicles equipped with AdvanceTrac� with roll stability control [RSC] only
- system check
- units (English/metric)
- language
- autolamp
- autolock
- autounlock
- running boards (if equipped)
- easy entry/exit seat
- park aid
- compass zone
- compass calibration
- oil life start value

System Check Displays

Selecting this function from the SETUP MENU causes the message center to cycle through each of the systems being monitored. For each of the monitored systems, the message center indicates either an OK message or a warning message for 2 seconds. For base instrument clusters, the TRIP/RESET button must be held down after pressing the TRIP/RESET button to cycle the messages through each of the systems being monitored. For high series instrument clusters, pressing the RESET control switch cycles the message center through each of the systems being monitored. The system check report is as follows:

- OIL LIFE RESET
- CHARGING SYSTEM
- WASHER FLUID
- DOOR AJAR
- EXTERIOR LAMPS
- BRAKE FLUID LEVEL
- PARK BRAKE
- FUEL LEVEL

Principles of Operation - Part 2