Getting unknown characters with the actual response when Reading ELM327

Hi, i am using arduino uno to read ELM327 using serial communication, i am able to send the AT commands an get the required response but i’m also getting some strange characters at the beginning. I can remove these characters from the beginning but i want to know why these strange characters is being printed the response.


#include <SoftwareSerial.h>

SoftwareSerial ELM(13, 12); // RX, TX
int CmdCount = 1;
byte inData;
char inChar;
String DisplayString = "";
long DisplayValue;
String SentMessage = "";
int ByteCount = 0;
long A;
int B;
int WorkingVal;
String WorkingString = "";
String BuildINString = "";
String message = "";

void setup() {


void loop() {

	if (Serial.available()) {
		ELM.println("AT DP");

void ReadMessage() {
	while (ELM.available() > 0)
		message = ELM.readString();

	message.replace(SentMessage, "");
	message.replace(">", "");
	message.replace("OK", "");
	message.replace("STOPPED", "");
	message.replace("SEARCHING", "");
	message.replace("NO DATA", "");
	message.replace("?", "");
	message.replace(",", "");

	String res = message.substring(0, 5);

Serial Monitor Output:

Q��eAUTO ISO 15765-4 (CAN 11/500)

Q���kAUTO ISO 15765-4 (CAN 11/500)

Q�#�5AUTO ISO 15765-4 (CAN 11/500)

@A��AUTO ISO 15765-4 (CAN 11/500)

Q��5AUTO ISO 15765-4 (CAN 11/500)

Q�!�kAUTO ISO 15765-4 (CAN 11/500)


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If you're going to do that then please be considerate enough to add links to the other places you cross posted. This will let us avoid wasting time due to duplicate effort and also help others who have the same questions and find your post to discover all the relevant information. When you post links please always use the chain links icon on the toolbar to make them clickable.

Okay, i thought this forum was not much active compare to stackexchange.

They're both extremely active. Quite a few of the same people too.