Principles of Operation

PRINCIPLES OF OPERATION

When installing a new instrument cluster, it is necessary to upload the module configuration information to the scan tool. Following installation of the instrument cluster, download the module configuration information and the vehicle identification number (VIN) from the scan tool in to the new instrument cluster.

Following installation of the instrument cluster, the instrument cluster and the powertrain control module (PCM) need to be mated. Refer to parameter reset procedure in Antitheft and Alarm Systems.

The following items are configurable:
- Odometer unit (English/metric)
- Speedometer calibration
- Backup warning chime (Japan only)
- 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
- Safety belt timer (Japan only)

The base and high series instrument clusters are configurable, hybrid electronic clusters (HEC) that contain a microprocessor, gauges, indicator lamps, and internal circuitry. The instrument cluster uses hardwired circuitry 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 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 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)
- Stability assist indicator

Gauges

Speedometer
The instrument cluster receives the vehicle speed sensor (VSS) signal from the powertrain control module (PCM) over the high speed controller area network (HS-CAN). The instrument cluster monitors the VSS input from the PCM 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 HS-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 HS-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 HS-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 5 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.

Indicators

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 HS-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 controller area network (MS-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 HS-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 HS-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 DTC is detected by the PCM. The instrument cluster receives the MIL data from the PCM over the HS-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 restraints control module (RCM) over the HS-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 HS-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 MS-CAN to illuminate the door ajar indicator.

Turn Signal Indicators
The SJB sends a message to the instrument cluster over the MS-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 MS-CAN to illuminate the high beam indicator.

Speed Control Indicator
The instrument cluster receives the speed control data from the PCM over the HS-CAN. When the speed control is engaged, the PCM provides a signal to the instrument cluster to illuminate the speed control indicator.

Wrench Warning Indicator (Base Instrument Cluster)
The instrument cluster receives the powertrain status from the PCM over the HS-CAN. When a powertrain system concern is detected, the PCM sends the instrument cluster a command signal to illuminate the 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 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 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 MS-CAN to the instrument cluster, which then illuminates the TPMS warning indicator.

Check Fuel Cap Indicator (Base Instrument Cluster)
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 HS-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 HS-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 PCM over the HS-CAN. When either 4x4 high or 4x4 low is selected, the PCM 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 HS-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.

Traction Control/Stability Assist Indicator
The traction control/stability assist indicator informs the driver that a traction control or stability assist event is taking place, by flashing the traction control/stability assist indicator during the event. The traction control/stability assist indicator illuminates constantly when a malfunction is detected in the traction control or stability assist system, or if the traction control or stability assist 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/stability assist indicator. The traction control/stability assist is controlled by the anti-lock brake system (ABS) module over the HS-CAN.