Principles of Operation
PRINCIPLES OF OPERATIONWhen installing a new instrument cluster, it is necessary to upload the module configuration to the diagnostic tool. Following installation of the instrument cluster, download the module configuration from the diagnostic tool into the new instrument cluster. 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
- flex fuel
- overspeed trip point
- seatbelt indicator timeout
- electronic automatic temperature control (EATC)
- seatbelt chime
The instrument cluster contains an analog speedometer, tachometer, fuel gauge and engine coolant temperature gauge. The instrument cluster receives the information over the controller area network (CAN) circuits. The instrument cluster carries out a display prove-out to verify that the warning/indicator lamps and monitored systems are operating correctly. When the key is turned to the ON position, the charging system, low oil pressure and the malfunction indicator lamp (MIL)/check engine illuminate until the engine starts.
Each time the ignition switch is turned from OFF to ON, the following instrument cluster warning indicators will prove out:
- air bag (6-second prove-out)
- ABS (3-second prove-out)
- BRAKE (3-second prove-out)
- charging system
- check engine (MIL)
- low fuel
- low oil pressure
- safety belt (60-second prove-out)
- traction control (if equipped) (3-second prove-out)
- THEFT (3-second prove-out)
- check fuel cap (3-second prove-out)
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. The instrument cluster receives the engine coolant temperature data from the PCM via the CAN circuits. 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
The fuel gauge receives the fuel level resistance from the fuel level sensor, part of the fuel pump module. To prevent the fuel gauge pointer from fluctuating as a result of excessive movement of fuel in the fuel tank, the instrument cluster provides a delay to the fuel gauge. If the fuel level is low, the resistance in the fuel level sensor will be low, causing the gauge to indicate empty (E). When the fuel level is high, the resistance in the fuel level sensor is high, and the gauge indicates full (F). The instrument cluster also turns on the low fuel indicator when the fuel gauge shows approximately 1/6 of a tank of fuel remaining or less.
Flex-Fuel Module
The flex-fuel module is a DC-AC-DC converter. It acts as an interface between the fuel pump module and the instrument cluster fuel gauge. 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).
Speedometer/Odometer
The instrument cluster receives the vehicle speed sensor (VSS) signal from the PCM via the CAN circuits. The instrument cluster monitors the VSS input from the PCM and commands the speedometer with a corresponding movement of the pointer.
Indicators
Air Bag
The instrument cluster is hardwired to the restraint 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 turning on the air bag warning indicator.
Anti-Lock Brake System (ABS)
The ABS warning indicator illuminates when the ABS module detects a fault in the system.
Brake System
The brake system warning indicator has a dual function. It illuminates when the parking brake is applied or when a low brake fluid condition exists in the brake master cylinder reservoir. The brake system warning indicator will illuminate when there is a pressure differential between the front and rear brake hydraulic systems.
Charging System
The PCM constantly monitors the generator regulator output. When the PCM detects a continuous high or low output signal, or when the ignition is ON and the engine is OFF, the PCM sends a CAN message to the instrument cluster to turn the charging system warning indicator on. When the ignition is ON with the engine running and the PCM determines that the set point for the regulator has been met, the PCM will send a CAN message to the instrument cluster to turn the charging system warning indicator off.
Low Fuel
The low fuel warning indicator is controlled by the instrument cluster and warns the driver when the fuel level is 1/6 of a tank or lower.
Low Oil Pressure
The instrument cluster is hardwired to the oil pressure switch. When there is low (under 41 kPa) or no oil pressure, the oil pressure switch remains closed, removing the ground to the instrument cluster. When sufficient oil pressure exists, the oil pressure switch opens, 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
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 turn on the safety belt warning indicator.
Check Fuel Cap
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
The traction control indicator flashes when the vehicle traction control is in active mode or is being controlled by the anti-lock brake system/traction control (ABS/TC) module. The instrument cluster receives the traction control signal from the ABS/TC module over the CAN circuits. The instrument cluster monitors the traction control signal and when the ABS/TC module detects a traction control concern, turns on the traction control indicator.
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 through the CAN circuits.
Theft
The theft indicator, located in the instrument cluster, is controlled by the signal sent via the CAN circuit from the PCM.