Tachometer

The tachometer displays engine RPM (speed), between 0 and 7000 RPM, anytime the power mode is RUN. The engine RPM is calculated by a discrete signal sent to the IPC from the PCM. The engine speed signal is active low, with a pull-up resistor located in the IPC and connected to switched battery voltage. The signal is a square wave with a 25 to 75 percent duty cycle. Each engine revolution is represented by two input pulses. Engine speed is calculated using the time difference between the two consecutive pulses. Accuracy of the final calculations are within 25 RPM.

The IPC determines the proper pointer position on the tachometer in order to display the engine speed. The DSPL MODE button is used to turn the display ON and OFF. The display will be ON when the speedometer gauge is ON and OFF when the speedometer gauge is OFF.