Instruments – circuit operation

INSTRUMENTS – CIRCUIT OPERATION

CIRCUIT OPERATION

Engine Coolant Temperature Gauge

The engine coolant temperature gauge sensor has the capability to sense from -40
C to +130
C. Petrol and Diesel resistance valves are different. Both Petrol and Diesel sensors are interfaced to the Instrument Cluster (Z142) via the BeCM (Z238). The resistance value then being represented by an A/D data transfer generating the required angular deflection on this gauge.         ]

Fuel Gauge

When the fuel tank level is low (“E”), the resistance value of the gauge sensor is 270 Ω for petrol and diesel engines. As the fuel level increases, the resistance of the sensor decreases. When the fuel tank is full, the resistance value of the sensor for petrol engines is 19 Ω and for diesel engines 25.8 Ω . When the fuel gauge sensors resistance value increases to 175 Ω (9 liters/2.25 US gallons, the low fuel warning light will illuminate to warn of the fuel status. Both Petrol and Diesel sensors are interfaced to the Instrument Cluster (Z142) via the BeCM (Z238). The resistance values then being represented by an A/D data transfer generating the required angular deflection on the gauge.

Speedometer

The signal to activate the gauge is originated at the ABS wheel sensors, transmitted to the ABS ECU (Z108) which then puts out a usable signal to the Instrument Cluster (Z142) of 8000 pulses per mile or 4972 pulses per kilometer. The signal is also transmitted to other ECU’s, such as the Engine Control Module (ECM) (Z132) and the Cruise Control ECU (Z121).

Tachometer

The tachometer will display the engine speed in R.P.M. It will derive the engine speed from the engine speed pulse train transmitted from the Engine Control Module (ECM) (Z132). The pulse rate for petrol engines will be 4 pulses per engine revolution. The pulse rate for diesel engines will be 3 pulses per engine revolution.

Audible Warning

Receipt of an audible warning request signal from a vehicle parameter/message condition shall cause the BeCM (Z238) to generate the required number of warning tones. The actuator sounder unit is located at the rear of the Instrument Cluster (Z142). See message listing for categories/priority and levels of audible warnings.