Principles of Operation

PRINCIPLES OF OPERATION

The instrument cluster is a hybrid electronic cluster (HEC) which receives and outputs information using both hardwired circuitry and the controller area network (CAN) communication circuits.

It is very important to understand:
- Where the input originates from.
- All the information necessary for a feature to operate.
- Which module(s) receive(s) the input or command message.
- If the module that received the input controls the output of the feature, or if it sends a message over the CAN to another module.
- Which module controls the output of the feature.

The instrument cluster carries out a prove-out when the ignition switch is turned from the OFF to the RUN position to verify the integrity of the warning indicators. The charging system warning indicator, the low oil pressure warning indicator and the malfunction indicator lamp (MIL) illuminate when the ignition switch is turned to the ON position, and then turn off when the engine is started and running normally. The safety belt warning indicator proves-out for 60 seconds and then turns off, or turns off when the safety belt is fastened. The following indicators prove-out when the ignition switch is turned to the ON position:
- Door ajar warning indicator (3 seconds)
- Anti-lock brake system (ABS) warning indicator (3 seconds)
- O/D OFF indicator (3 seconds)
- Air bag warning indicator (6 seconds)
- Brake warning indicator (3 seconds)
- Door ajar warning indicator (3 seconds)
- Shift-up indicator (3 seconds)
- Low fuel warning indicator (3 seconds)
- Traction control indicator (3 seconds)
- Check fuel cap indicator (3 seconds)
- Passive anti-theft system (PATS) indicator (3 seconds)

Tachometer
Engine speed data is transmitted to the instrument cluster from the powertrain control module (PCM) over the communication network.

Speedometer
The instrument cluster receives the vehicle speed signal from the PCM over the communication network and displays it on the speedometer gauge. If the instrument cluster does not receive a vehicle speed signal, the speedometer defaults to 0 km/h (0 mph).

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 low (15 ohms ± 2 ohms). When the fuel level is high, the resistance in the unit is high (160 ohms ± 4 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 when refueling 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 one 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 15 ohms ± 2 ohms and 160 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 transaxle is in PARK (P) (automatic transaxles), or the parking brake applied (manual transaxles).
- 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 transaxle is put into the PARK (P) position (automatic transaxles) or when the parking brake is applied (manual transaxles). 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 transaxle is shifted out of PARK (P) or the parking brake is released, the fuel gauge strategy reverts to the anti-slosh mode. This 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.

Temperature Gauge
Engine coolant temperature information is received by the instrument cluster from the PCM over the communication network. If the engine coolant temperature information is missing or invalid, the temperature gauge indicates below the cold (C) position.

Odometer/Trip Odometer
The odometer and trip odometer are displayed in the integrated circuit LCD display. The instrument cluster records the total mileage of the vehicle using information received from the PCM, and electronically displays this information in the LCD. If this information is not received, the LCD displays all dashes.

Traction Control Indicator
The instrument cluster provides a traction control indicator to inform the driver when the traction control is active. The traction control signal comes from the ABS module and is sent to the instrument cluster over the communication network. When the traction control is in the active mode the ABS module provides a ground signal to the instrument cluster and the traction control indicator is turned on.

Check Fuel Cap Indicator
The check fuel cap indicator is used to indicate significant leaks in the fuel tank evaporative system due to a loose fuel cap. 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 communication network. Once the PCM detects a loose fuel cap and the check fuel cap indicator is illuminated, the check fuel cap indicator remains illuminated until the fuel cap is secured and the vehicle has been running for several minutes or the ignition has been cycled once.

Speed Control Indicator
The speed control indicator is hardwired to the speed control module. When the speed control is engaged, the speed control module provides a ground to the instrument cluster to illuminate the speed control indicator.

Low Fuel Warning Indicator
The instrument cluster uses fuel level data supplied by the hardwired fuel pump module to control the low fuel warning indicator, which illuminates when the fuel drops to a pre-determined level.

Brake Warning Indicator
The brake warning indicator is controlled by multiple inputs and illuminates under multiple conditions. The instrument cluster is hardwired to the parking brake switch and illuminates when the parking brake is set. The instrument cluster is also hardwired to the brake fluid level switch and illuminates when the brake fluid level is low. Finally, the ABS module sends the instrument cluster a communication message, which commands the brake warning indicator on when a base brake system concern or ABS concern exists.

Safety Belt Indicator
The instrument cluster safety belt indicator illuminates if the driver safety belt is not fastened when the ignition switch is turned to the RUN position. The instrument cluster receives the safety belt status from the restraints control module (RCM) over the communication network.

ABS Warning Indicator
When an ABS failure, open control circuit, or a control circuit short to battery occurs, the instrument cluster illuminates the ABS warning indicator.

Malfunction Indicator Lamp (MIL)
The instrument cluster receives the MIL status from the PCM over the communication network. The PCM sends a command to the instrument cluster to illuminate the MIL indicator when a DTC is registered in the PCM that affects exhaust emissions.

PATS Indicator Lamp
The anti-theft indicator provides system prove-out and interface to the driver as to the operating condition of the PATS. This is controlled by the PCM on hardwired circuitry. When the PATS is enabled in the PCM, the PATS indicator proves out when the ignition switch is switched to the RUN position and flashes when the ignition switch is in the OFF or ACC position.

O/D OFF Indicator
The instrument cluster receives the O/D OFF indicator status from the PCM over the communication network. When the overdrive function is turned off, the PCM sends a command to the instrument cluster to turn on the O/D OFF indicator. When a powertrain concern exists, the O/D OFF indicator flashes amber and illuminates green when overdrive is selected off.

Engine Oil Pressure Warning Indicator
The engine oil pressure warning indicator is hardwired to the engine oil pressure switch. When the ignition switch is in the RUN position with the engine off, the oil pressure switch closes and the oil pressure warning indicator illuminates. After the engine is started and the oil pressure builds up, the oil pressure switch opens, grounding the control circuit to the instrument cluster and turning off the oil pressure warning indicator.

Door Ajar Warning Indicator
The door ajar warning indicator is controlled by the generic electronic module (GEM), the anti-theft module, and the door, liftgate and luggage compartment lid switches. The instrument cluster receives a ground signal from the GEM when a door or liftgate is opened or not fully closed and illuminates the door ajar warning indicator.

Air Bag Warning Indicator
The supplemental restraint system (SRS) is monitored and controlled by the RCM. The status of the supplemental system is sent from the RCM to the instrument cluster through the communication network. The air bag warning indicator illuminates when the RCM sends a signal to the instrument cluster.

Charging System Warning Indicator
The instrument cluster receives the charging system status from the PCM over the communication network. The PCM controls the charging system and the charging system warning indicator. The PCM is therefore responsible for turning the lamp off once the system is running, and for illuminating it under fault conditions (including stall conditions).

Shift Up Indicator
The shift up indicator illuminates to indicate that the engine system determines this to be the optimal point for shifting into a higher gear to maintain peak efficiency and fuel economy. The instrument cluster receives the shift up status from the PCM which then transmits a command to the instrument cluster over the communication network to illuminate the shift up indicator.

High Beam Indicator
The high beam indicator is hardwired to the instrument cluster and illuminates when the multifunction switch is in the HIGH BEAM position by sending a battery signal to the instrument cluster.

Turn/Hazard Indicators
The instrument cluster provides a ground for the RH and LH turn indicators. When the multifunction switch is in the RH or LH TURN position, voltage is supplied to the instrument cluster from the GEM through hardwired circuitry and the RH or LH turn indicators flash on and off.