Tachometer (With Digital Cluster)

The tachometer displays engine RPM (speed), between 0 and 7000 RPM. 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 2 input pulses. Engine speed is calculated using the time difference between the 2 consecutive pulses. Accuracy of the final calculations are within 25 RPM. The tachometer cannot be reset by the driver. The tachometer is displayed as XXXX RPM TACHOMETER (the XXX represents the calculated engine RPM value). The value will range between 0 and 7000 RPM.