Understanding your Renault’s engine performance is crucial for maintenance and diagnostics. One of the key parameters to monitor is engine speed, measured in revolutions per minute (RPM). Thanks to the On-Board Diagnostics II (OBD2) system, accessing this data is easier than ever. This article delves into how to use an OBD2 scanner or DIY tools like Arduino to request and interpret engine speed data (PID 0C) from your Renault vehicle.
Understanding OBD2 PID 0C: Engine Speed
OBD2 Parameter IDs (PIDs) are codes used to request specific data from a vehicle’s Engine Control Unit (ECU). PID 0C is the standard code for requesting “Engine RPM”. When you send this request to your Renault’s OBD2 port, the ECU responds with data representing the current engine speed.
This data is invaluable for:
- Diagnostics: Identifying engine idling issues, misfires, or performance problems.
- Performance Monitoring: Tracking engine RPM under different driving conditions.
- DIY Car Repair: Verifying sensor readings and troubleshooting engine-related faults.
- Custom Projects: Integrating engine speed data into custom dashboards or logging systems.
Requesting OBD2 PID 0C with Arduino and MCP2515
For enthusiasts and DIYers, Arduino combined with an MCP2515 CAN bus controller offers a flexible platform to interact with your Renault’s OBD2 system. Let’s examine a basic Arduino sketch designed to request PID 0C and display the received data.
#include <mcp_can.h>
#include <SPI.h>
#define standard 0 // Extended ID for Renault
#if standard == 1
// Standard ID (Not typically used for functional requests on modern vehicles)
#else
// Extended ID for Renault (Example - may vary based on model)
#define LISTEN_ID 0x98DAF101
#define REPLY_ID 0x98DA01F1
#define FUNCTIONAL_ID 0x98DB33F1
#endif
// CAN TX Variables
unsigned long prevTx = 0;
unsigned int invlTx = 1000; // Send request every 1 second
byte txData[] = {0x02, 0x01, 0x0C, 0x55, 0x55, 0x55, 0x55, 0x55}; // Request PID 0C (Engine Speed)
// CAN RX Variables
unsigned long rxID;
byte dlc;
byte rxBuf[8];
char msgString[128];
// CAN Interrupt and Chip Select Pins
#define CAN0_INT 2
MCP_CAN CAN0(10); // CS Pin for MCP2515
void setup(){
Serial.begin(115200);
while(!Serial);
// Initialize MCP2515
if(CAN0.begin(MCP_STDEXT, CAN_500KBPS, MCP_8MHZ) == CAN_OK) {
Serial.println("MCP2515 Initialized Successfully!");
} else {
Serial.println("Error Initializing MCP2515... Check connections!");
while(1);
}
// CAN Filters - Configure to receive relevant messages (Extended IDs for Renault example)
CAN0.init_Mask(0,0x90FF0000);
CAN0.init_Filt(0,0x90DA0000);
CAN0.init_Filt(1,0x90DB0000);
CAN0.init_Mask(1,0x90FF0000);
CAN0.init_Filt(2,0x90DA0000);
CAN0.init_Filt(3,0x90DB0000);
CAN0.init_Filt(4,0x90DA0000);
CAN0.init_Filt(5,0x90DB0000);
CAN0.setMode(MCP_NORMAL);
pinMode(CAN0_INT, INPUT);
Serial.println("Simple CAN OBD-II PID Request");
}
void loop(){
if(!digitalRead(CAN0_INT)){ // Check for incoming CAN messages
CAN0.readMsgBuf(&rxID, &dlc, rxBuf); // Read the message
// Display received CAN data
if((rxID & 0x80000000) == 0x80000000) {
sprintf(msgString, "Extended ID: 0x%.8lX DLC: %1d Data:", (rxID & 0x1FFFFFFF), dlc);
} else {
sprintf(msgString, "Standard ID: 0x%.3lX DLC: %1d Data:", rxID, dlc);
}
Serial.print(msgString);
if((rxID & 0x40000000) == 0x40000000){
sprintf(msgString, " REMOTE REQUEST FRAME");
Serial.print(msgString);
} else {
for(byte i = 0; i<dlc; i++){
sprintf(msgString, " 0x%.2X", rxBuf[i]);
Serial.print(msgString);
}
}
Serial.println();
}
// Send PID 0C request periodically
if((millis() - prevTx) >= invlTx){
prevTx = millis();
if(CAN0.sendMsgBuf(FUNCTIONAL_ID, 8, txData) == CAN_OK){
Serial.println("Message Sent Successfully!");
} else {
Serial.println("Error Sending Message...");
}
}
}This code initializes the MCP2515 CAN controller, sets up filters to listen for relevant CAN messages (using extended IDs which are common in modern vehicles like Renault), and periodically sends a request for PID 0C. Let’s break down key parts:
#include <mcp_can.h>and#include <SPI.h>: Includes necessary libraries for MCP2515 CAN communication and SPI communication with Arduino.#define standard 0and ID Definitions: Configures the code to use Extended CAN IDs, which are more commonly used in modern vehicles. The example IDs (LISTEN_ID,REPLY_ID,FUNCTIONAL_ID) are examples and might need to be adjusted based on your specific Renault model and CAN bus configuration. It’s crucial to verify the correct CAN IDs for your Renault.byte txData[] = {0x02, 0x01, 0x0C, ...}: This array defines the CAN message payload for the OBD2 PID request.0x02: Specifies the number of data bytes following (Service ID + PID).0x01: OBD2 Service ID for “Show current data”.0x0C: The PID code for “Engine RPM”.0x55, 0x55, ...: Padding bytes – often filled with0x55or0x00.
CAN0.sendMsgBuf(FUNCTIONAL_ID, 8, txData): Sends the CAN message with the definedFUNCTIONAL_IDandtxDatato request PID 0C.CAN0.readMsgBuf(&rxID, &dlc, rxBuf): Reads incoming CAN messages and extracts the ID (rxID), data length code (dlc), and data bytes (rxBuf).- Serial Output: The code prints received CAN messages to the serial monitor, allowing you to see the raw data and diagnose any issues.
Troubleshooting Your Renault OBD2 PID 0C Request
The user provided an image indicating an issue with their PID 0C request.
Arduino Serial Monitor Output Showing Potential OBD2 Request Issue
Based on the question and the code, here are potential troubleshooting steps when you encounter problems requesting OBD2 data from your Renault:
-
Verify CAN Bus Connection: Double-check your wiring between the MCP2515 module, Arduino, and your Renault’s OBD2 port. Ensure proper connections for CAN_H, CAN_L, VCC, GND, and SPI pins. Incorrect wiring is a common cause of communication failure.
-
Confirm CAN Bus Speed: The code uses
CAN_500KBPS. While 500kbps is standard for OBD2, some Renault models might use different speeds for specific CAN buses. Consult Renault technical documentation if available, or try common OBD2 speeds like 250kbps to test. -
Check CAN IDs (Crucial for Renault): The example code uses extended CAN IDs (
0x98DAF101,0x98DA01F1,0x98DB33F1). These IDs are likely examples and may not be correct for your specific Renault model. Renault vehicles can use various CAN protocols and IDs.- Research Renault Specific CAN IDs: Search online forums, Renault repair manuals, or Obd2 Renault specific resources for correct CAN IDs for functional requests and diagnostics on your vehicle model and year.
- CAN Bus Sniffing: Use a CAN bus sniffer tool (if available) to monitor CAN traffic on your Renault’s OBD2 port. This will help you identify the correct IDs used for communication.
-
OBD2 Protocol Compatibility: Ensure your Renault uses a standard OBD2 protocol (like ISO 15765-4 CAN, which is common). While OBD2 is a standard, subtle variations or proprietary implementations can sometimes exist.
-
ECU Response and Service $01: The Service ID
0x01(Show current data) is generally supported, but ensure your Renault ECU actually responds to this service and PID 0C. Some ECUs might require specific initialization sequences or security access before responding to certain requests. -
Code Logic and Filters: Review the Arduino code for any logical errors in request sending or data reception. The CAN filters in the
setup()function are designed to receive messages with specific ID ranges. If the Renault ECU responds with IDs outside these filters, you won’t see the data. Adjust the filters based on your research of Renault CAN IDs. -
OBD2 Scanner Verification: Before diving deep into DIY solutions, test with a known working OBD2 scanner on your Renault. If a standard scanner can successfully read engine RPM, it confirms that the OBD2 port and ECU are functioning correctly, and the issue likely lies within your Arduino setup or code.
Expanding Your Renault OBD2 Diagnostics
Once you successfully retrieve engine speed, you can explore other valuable OBD2 PIDs for your Renault:
- PID 0D: Vehicle Speed: Monitor your Renault’s speed as reported by the ECU.
- PID 05: Engine Coolant Temperature: Track engine temperature for overheating warnings and diagnostics.
- PID 0F: Intake Air Temperature: Useful for performance tuning and diagnosing intake system issues.
- PID 10: Mass Air Flow (MAF) Rate: Essential for fuel mixture and engine load calculations.
- PID 04: Calculated Engine Load: Indicates the percentage of maximum engine power being used.
You can modify the txData array in the Arduino code to request these different PIDs by changing the third byte (e.g., 0x0D for vehicle speed, 0x05 for coolant temperature, etc.). Refer to a comprehensive OBD2 PID list for all available parameters.
Conclusion
Accessing OBD2 data from your Renault opens up a world of diagnostic and monitoring possibilities. By understanding OBD2 PIDs like 0C for engine speed and utilizing tools like Arduino and MCP2515, you can gain valuable insights into your vehicle’s performance and health. Remember to verify CAN IDs and troubleshoot connection and code issues systematically to ensure successful OBD2 communication with your Renault. Exploring further PIDs will empower you with deeper knowledge and control over your Renault’s diagnostics.
