OBD for an automobile

//Project on creation of OBD design
//Serial Monitor for the output
//Serial Monitor is on the right topmost corner


#define ECHOPIN 3   //input
#define TRIGPIN 2   //output
float duration;
float duration1;
int distance;
int distance1;

void setup() {
Serial.begin(9600);
pinMode(11,INPUT);
pinMode(10,OUTPUT);
pinMode(13,OUTPUT);
pinMode(11,INPUT);
pinMode(10,OUTPUT);
pinMode(13,OUTPUT);


}

void loop() {
digitalWrite(10,LOW);
delayMicroseconds(2);
digitalWrite(10,HIGH);
delayMicroseconds(10);
digitalWrite(10,LOW);
float duration = pulseIn(11,HIGH);
distance= duration*0.034/2;
Serial.println("\n Brakepads  : ");
Serial.print(distance);
Serial.println("mm");
if(distance>12)
{
  digitalWrite(13,HIGH);
  delay(200);
  Serial.println(" \n Thickness of Brakepads is more than the limit");
  Serial.println("\n  Time to change it");
 
}

else if(distance>=5){
  Serial.println("normal, brakepads are ok");
  digitalWrite(13,LOW);
  delay(200);
}
else if(distance<5)
{Serial.println("They are torn");
digitalWrite(13,HIGH);
delay(200);
}
digitalWrite(10,LOW);
delayMicroseconds(2);
digitalWrite(10,HIGH);
delayMicroseconds(10);
digitalWrite(10,LOW);
float duration1 = pulseIn(11,HIGH);
distance1= duration1*0.034/2;
Serial.println("\n Engine Coolant Level : ");
Serial.print(distance);
Serial.println("cm");
if(distance>8)
{
  digitalWrite(13,HIGH);
  delay(200);
  Serial.println(" \n coolant is very low as per the limit");
  Serial.println("\n  time to change it");
 
}

else if(distance>=5){
  Serial.println("normal, coolant level is  ok");
  digitalWrite(13,LOW);
  delay(200);
}
}