I am using an Arduino UNO along with a Cooking Hacks CAN Bus Module and Multiprotocol Radio Shield. The CAN module is connected to the radio shield which is plugged into the Arduino. I got this radio shield keeping future applications in mind where I can combine multiple protocols, for eg. CAN and Bluetooth. I connected them through an OBD2-DB9 cable to the car's OBD port.

I managed to get the CAN messages on the serial monitor and started playing around with the headlamp switch which I know is connected to the CAN BUS. However, upon analysing the received CAN messages, I noticed that the headlamp messages weren't received by the Arduino. In fact, I didn't see any relevant CAN message on the serial monitor. I know the CAN ID for the headlamp messages having used a Kvaser CAN Sniffer earlier.

Also, in order to test the setup, I uploaded a sample sketch with standard OBD functions like Vehicle Speed, Throttle Position, Fuel level etc and the values received were highly incorrect. With a stationary vehicle with the ignition ON but the engine OFF, I received values of 256 Km/hr for vehicle speed, 3178 rpm for engine rpm , 257% for Fuel Level etc. I don't know why this is happening. Can anybody please help me?

CAN Receiver Code:

    #include <arduinoClasses.h>
    #include <arduinoMultiprotocol.h>
    #include <arduinoUART.h>
    #include <arduinoUtils.h>
    #include <arduinoCAN.h>
    #include <Wire.h>
    #include <SPI.h>

    // ID numbers
    #define IDWAITED 200
    #define OWNID 100
   
    CAN myCAN = CAN();

    void setup() {
    Serial.begin(115200);
    delay(100);

    // CAN BUS speed:
    // 1:   1Mbps
    // 500: 500Kbps  
    // 250: 250Kbp
    // 125: 125Kbps
    myCAN.begin(500);  
    }

    void loop() {
    //Receive data
    if (myCAN.messageAvailable()==1) {

   // Read the last message received.        
    myCAN.getMessage(&myCAN.messageRx);

    // Print in the serial monitor the received message
    myCAN.printMessage(&myCAN.messageRx);
    }
    }

OBD CODE:

    #include <Wire.h>
    #include <arduinoUtils.h>
    #include <arduinoCAN.h>
    #include <SPI.h>

    CAN myCAN = CAN();
    void setup() {
  
    Serial.begin(115200);
    delay(100);
    // Configuring the BUS at 500 Kbit/s
    myCAN.begin(500);   

    Serial.println("CANBUS initialized at 500 KBits/s");  
    Serial.println();
    }

    void loop() {
   
    int vehicleSpeed = myCAN.getVehicleSpeed(); 
    int engineRPM = myCAN.getEngineRPM(); 
    int fuelLevel = myCAN.getFuelLevel();
    int throttlePosition = myCAN.getThrottlePosition();
   
    Serial.print(F("\tVehicle Speed (km/hr) =>  ")); 
    Serial.print(vehicleSpeed);

    Serial.print(F("\tEngine RPM =>  ")); 
    Serial.print(engineRPM);

    Serial.print(F("\tFuel Level (%) =>  ")); 
    Serial.print(fuelLevel);

    Serial.print(F("\tThrottle Position (%) =>  ")); 
    Serial.print(throttlePosition);
    delay(1000); 
    }