OBD-II Diagnostics

Interface

OBD-II (On-Board Diagnostics) is a standardized port for vehicle diagnostics. It provides direct access to the CAN bus and standard diagnostic services.

OBD-II Modes

obd2-modes.txt
text 
# Standard OBD-II service modes (PIDs):
Mode 01: Current powertrain data
Mode 02: Freeze frame data  
Mode 03: Emission diagnostic codes
Mode 04: Clear diagnostic codes
Mode 05: Oxygen sensor monitoring
Mode 06: On-board monitoring test results
Mode 07: Pending diagnostic codes
Mode 08: Control on-board systems
Mode 09: Vehicle information (VIN, calibration)
Mode 0A: Permanent diagnostic codes

# Example: Request RPM (Mode 01, PID 0C)
# Send: 7DF#02010C0000000000
# Response: 7E8#04410C0FA00000

OBD-II Tools

obd2-python.py
python 
# Python OBD library
pip install obd

import obd
connection = obd.OBD()  # Auto-connects

# Query standard PIDs
rpm = connection.query(obd.commands.RPM)
speed = connection.query(obd.commands.SPEED)
print(f"RPM: {rpm.value}, Speed: {speed.value}")

# Get VIN
vin = connection.query(obd.commands.VIN)

# Read DTCs (Diagnostic Trouble Codes)
dtcs = connection.query(obd.commands.GET_DTC)

# ELM327-based tools
# Send raw AT commands
ATZ   # Reset
ATSP0 # Auto protocol
0100  # Supported PIDs 01-20
0902  # Request VIN

UDS

Many vehicles support UDS (Unified Diagnostic Services - ISO 14229) which provides extended diagnostic capabilities including ECU flashing.

Related Topics

CAN Attacks

Keyless Entry