Principles of Operation

PRINCIPLES OF OPERATION

When installing a new instrument cluster, it is necessary to upload the module configuration to the scan tool. Following installation of the instrument cluster, download the module configuration from the scan tool into the new instrument cluster. Refer to Information Bus (Module Communications Network).

The following items are configurable:
- Speedometer
- Outside air temperature
- Compass
- Anti-lock brake system (ABS)
- Anti-lock brake system/traction control (ABS/TC)
- Overspeed warning chime
- Reverse warning chime
- Overspeed trip point
- Seatbelt indicator timeout
- Electronic automatic temperature control (EATC)
- Seatbelt chime

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 turns off when the engine is started and running normally. The seat belt warning indicator proves-out for 60 seconds and then turns off, or turns off when the seat belt is fastened. The following indicators prove-out for 3 seconds when the ignition switch is turned to the ON position:
- Air bag
- ABS
- BRAKE
- Traction control (if equipped)
- THEFT
- Check fuel cap

Engine Coolant Temperature Gauge
The powertrain control module (PCM) receives the engine coolant temperature status through hardwired circuitry from the engine coolant temperature (ECT) sensor. The instrument cluster receives the engine coolant temperature data from the PCM over the communication network. The instrument cluster monitors the engine coolant temperature data received from the PCM and commands the engine coolant temperature gauge indication with a corresponding movement of the pointer.

Fuel Gauge

NOTE:
- The fuel pump module may also be called the fuel sender or fuel tank unit.
- The resistance of the fuel level sensors differ depending on whether the fuel level sensor is designed for gasoline or flex-fuel and cannot be interchanged. Be sure to use only fuel level sensors designed for gasoline.

On gasoline engines, 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).

If equipped with flex-fuel, the basic fuel level indication is the same except that the flex-fuel vehicles incorporate the use of a flex-fuel module. The flex-fuel module is a DC-AC interface used primarily to prevent electrochemical reactions with the alcohol in the fuel. The flex-fuel module applies an AC voltage to the fuel level sender to measure the fuel sender resistance changes based on current fuel level and returns a modified resistance matching the fuel level to the instrument cluster. When the fuel level is low, the resistance in the unit is low (7 ohms ±2 ohms). When the fuel level is high, the resistance in the unit is high (138 ohms ±4 ohms). The flex-fuel module is located in the instrument panel, on the right side of the steering column, just behind the integrated control panel (ICP).

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 15 ohms ±2 ohms and 160 ohms ±4 ohms (gasoline engines), or 7 ohms ±2 ohms and 138 ohms ±4 ohms(flex-fuel engines). 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 during 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.

Speedometer/Odometer
The instrument cluster receives the vehicle speed sensor (VSS) signal from the PCM over the communication network. The instrument cluster monitors the VSS input from the PCM and commands the speedometer with a corresponding movement of the pointer.

Tachometer
The instrument cluster receives tachometer information from the PCM over the communication network.

Air Bag Warning Indicator
The instrument cluster is hardwired to the restraints control module (RCM). If an air bag system concern is detected, a diagnostic trouble code (DTC) is logged and the RCM provides a ground path to the instrument cluster illuminating the air bag warning indicator. Refer to Air Bag Systems.

Anti-Lock Brake System (ABS) Warning Indicator
The ABS warning indicator illuminates when the ABS module detects a fault in the system. Refer to Antilock Brakes/Traction Control Systems.

Brake Warning Indicator

NOTE: When the anti-lock brake system (ABS) module detects an electronic brake distribution (EBD) fault, the ABS module sends a message to the instrument cluster. Whenever the instrument cluster receives an EBD message from the ABS module, the instrument cluster turns on both the brake warning indicator and the ABS warning indicator simultaneously.

The instrument cluster turns on the brake warning indicator when the parking brake is applied or when a low brake fluid condition exists in the brake master cylinder reservoir.

Charging System Warning Indicator
The PCM constantly monitors the generator regulator output. When the PCM detects a continuous high or low output signal, or when the ignition switch is in the ON position and the engine is off (KOEO), the PCM sends a message to the instrument cluster to illuminate the charging system warning indicator. When the ignition switch is in the ON position with the engine running, and the PCM determines that the set point for the regulator has been met, the PCM will send a message to the instrument cluster to turn off the charging system warning indicator.

Low Fuel Warning Indicator
The low fuel warning indicator is controlled by the instrument cluster and warns the driver when the fuel level is 1/8 of a tank or lower.

Low Oil Pressure Warning Indicator
The instrument cluster is hardwired to the oil pressure switch. When there is low (under 41 kPa [6 psi]) or no oil pressure, the oil pressure switch is 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. The instrument cluster monitors the oil pressure ground signal and commands the low oil pressure warning indicator on or off according to engine oil pressure.

Safety Belt Warning Indicator
The RCM monitors the safety belt position through the safety belt buckle switch. 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.

Check Fuel Cap Warning Indicator
The PCM monitors pressure in the fuel evaporative system and detects massive or critical losses of pressure. When a critical loss of pressure in the fuel evaporative system is detected, the PCM provides a ground and the instrument cluster illuminates the check fuel cap warning indicator.

Traction Control Indicator
The traction control indicator flashes when the vehicle traction control is in active mode or when the ABS module detects a traction control system fault. The instrument cluster receives the traction control signal from the ABS module over the communication network. The instrument cluster monitors the traction control signal and when the ABS module detects a traction control concern, the traction control indicator is illuminated.

Malfunction Indicator Lamp (MIL)
The MIL is illuminated when a DTC is detected by the PCM. The instrument cluster receives the MIL data from the PCM over the communication network.

Theft Indicator
The theft indicator alerts the operator that an anti-theft system malfunction has occurred or that the anti-theft system is armed when the ignition switch is in the OFF or ACC position. The theft warning indicator operates with a message over the communication circuits from the PCM when the ignition switch is in the RUN and START positions and is controlled by the instrument cluster in the OFF and ACC positions.

High Beam Indicator
The high beam indicator illuminates when the multifunction switch is in the HIGH BEAM ON position and sends a voltage signal to the instrument cluster.

Right and Left Turn Indicator
The right and left turn indicators illuminate when the multifunction switch is in either the TURN SIGNAL ON position or the HAZARD LAMPS ON position and sends a voltage signal to the instrument cluster.

CRUISE Control Indicator
The instrument cluster receives the speed control data from the PCM through the communication network. When the speed control is engaged, the PCM provides a signal to the instrument cluster to illuminate the CRUISE control indicator.