Algunos cambios menores, pruebalo y nos dices que tal funciona
void loop() {
unsigned int uS1 = sonar.ping_cm(); // activates the first sensor
delay(50); // wait 50ms
unsigned int uS2 = sonar1.ping_cm(); // activate the second sensor
delay(50); // wait 50ms
Serial.print("Ping: ");
Serial.print(us1);
Serial.println("cm");
Serial.print("Ping1: ");
Serial.print(us2);
Serial.println("cm");
delay(1000);
lcd.begin(16, 2);
lcd.print(" Tinaco= ");
lcd.setCursor(1,1);
lcd.print(" Cisterna=");
if (uS1 < 20) { //if an object is less than 20 cm away
//from the front sensor,
digitalWrite(Motor, HIGH);
//the motor will rotate forward.
// lcd.setCursor(X,Y); // ajustar X,Y a lo que corresponda
lcd.print("Motor ON");
}
if (uS2 < 20 | // if an object is less than 20 cm away from the back sensor,
(uS1 < 20 && uS2 < 20 ) | // if an object is less than 20 cm away from the right and left sensors,
(uS1 > 20 && uS2 > 20 )) {
digitalWrite(Motor, LOW); //the motor will rotate backwards.
// lcd.setCursor(X,Y); // ajustar X,Y a lo que corresponda
lcd.print("Motor OFF");
}
delay(5000);
}