Understanding your vehicle’s health is crucial in modern car ownership. The On-Board Diagnostics II (OBD2) system is your car’s built-in self-diagnostic system, acting as a window into its inner workings. By learning how to read data from an OBD2 scanner, you can gain valuable insights into your vehicle’s performance, diagnose potential issues, and make informed maintenance decisions.
This guide provides a comprehensive introduction to reading data from OBD2 scanners. Whether you’re a car enthusiast, a DIY mechanic, or simply a vehicle owner wanting to understand your car better, this guide will equip you with the knowledge to effectively use an OBD2 scanner and interpret the data it provides.
You can also watch our OBD2 intro video above – or get the PDF
What is OBD2 and Why is Reading Data Important?
OBD2, or On-Board Diagnostics II, is a standardized protocol implemented in most vehicles since the mid-1990s. It’s designed to monitor various vehicle systems, particularly emissions-related components. When something goes wrong, the OBD2 system generates Diagnostic Trouble Codes (DTCs) and provides access to real-time data about the vehicle’s operation.
You’ve likely encountered OBD2 when your car’s check engine light illuminates. This light signals that the OBD2 system has detected an issue. Mechanics use OBD2 scanners to communicate with your car’s computer, retrieve these DTCs, and access live data to diagnose the problem.
By learning how to read data from an OBD2 scanner, you can:
- Diagnose car problems yourself: Understand what’s triggering the check engine light and potentially fix minor issues without a mechanic.
- Monitor vehicle health: Track real-time parameters like engine temperature, speed, RPM, and fuel efficiency to ensure optimal performance.
- Save on repair costs: Get a head start on diagnosing issues before they become major problems, potentially saving money on expensive repairs.
- Make informed decisions: Gain insights into your car’s condition before buying a used vehicle or performing modifications.
Essentially, reading data from an OBD2 scanner empowers you to become more proactive and informed about your vehicle’s maintenance and performance.
Understanding the OBD2 Connector and Protocols
To read data from an OBD2 scanner, you first need to connect the scanner to your vehicle’s OBD2 port. This port is standardized across most vehicles and is typically located within a few feet of the steering wheel, though its exact location can vary. It’s a 16-pin connector, as defined by the SAE J1962 standard and its international equivalent ISO 15031-3.
While the physical connector is standardized, the communication protocols used over OBD2 have evolved. Initially, several protocols were used, including:
- SAE J1850 VPW & PWM: Used primarily in older GM and Ford vehicles.
- ISO 9141-2 & ISO 14230-4 (KWP2000): Common in European and Asian vehicles.
However, since 2008 in the US (and later in other regions), the Controller Area Network (CAN bus) protocol (ISO 15765-4) became mandatory for OBD2 in most cars. CAN bus is a robust and high-speed communication network, allowing for efficient data exchange between different electronic control units (ECUs) in your vehicle. Today, CAN bus is the dominant protocol for OBD2.
When you read data from an OBD2 scanner on a modern vehicle, you’re most likely communicating over CAN bus. Pins 6 (CAN High) and 14 (CAN Low) of the OBD2 connector are dedicated to CAN communication.
OBD2 Modes and Parameter IDs (PIDs) – Key to Reading Data
The core of reading data from an OBD2 scanner lies in understanding OBD2 modes and Parameter IDs (PIDs). OBD2 communication is based on a request-response system. Your OBD2 scanner sends a request to the vehicle, and the vehicle responds with the requested data.
OBD2 defines ten standard “services” or modes, each identified by a hexadecimal number (01 to 0A). These modes categorize different types of diagnostic information. The most commonly used modes when learning how to read data from an OBD2 scanner are:
- Mode 01: Show current data. This mode is used to access real-time data parameters, also known as PIDs. This is the most frequent mode used for monitoring live data.
- Mode 02: Show freeze frame data. When a DTC is stored, the system can also store a “freeze frame” of data parameters that were present when the fault occurred.
- Mode 03: Show stored Diagnostic Trouble Codes. This mode retrieves the currently stored DTCs that are causing the check engine light to be on.
- Mode 04: Clear Diagnostic Trouble Codes and stored values. This mode allows you to reset the check engine light and clear stored DTCs (use with caution and understanding).
- Mode 09: Request vehicle information. This mode is used to request vehicle-specific information, such as the Vehicle Identification Number (VIN).
Within each OBD2 mode, Parameter IDs (PIDs) are used to specify the exact data you want to retrieve. PIDs are also hexadecimal codes. For example, in Mode 01 (Show current data), PID 0C requests engine RPM, and PID 0D requests vehicle speed.
To read data from an OBD2 scanner, you essentially select an OBD2 mode and then request specific PIDs within that mode. The vehicle’s ECU then responds with the data corresponding to those PIDs.
Step-by-Step Guide: How to Read Data from an OBD2 Scanner
Now, let’s walk through the practical steps on how to read data from an OBD2 scanner:
Step 1: Connect the OBD2 Scanner
- Locate the OBD2 port in your vehicle. Refer to your car’s manual if you’re unsure of its exact location. It’s usually under the dashboard on the driver’s side.
- Plug your OBD2 scanner securely into the port.
Step 2: Power On and Establish Connection
- Turn your vehicle’s ignition to the “ON” position. You don’t need to start the engine, but the electrical systems should be active.
- Power on your OBD2 scanner. Most scanners will power on automatically once connected and the ignition is on.
- The scanner will typically attempt to establish a connection with your vehicle’s computer. Follow the scanner’s on-screen prompts if necessary. This may involve selecting the correct communication protocol if your scanner prompts you (though most modern scanners auto-detect CAN bus).
Step 3: Navigate Scanner Menus to Read Data
-
Once connected, navigate the scanner’s menu using its buttons or touchscreen. The menu options will vary depending on your specific OBD2 scanner, but common options include:
- Read Codes (or Diagnostic Trouble Codes – DTCs): Select this option to retrieve stored DTCs (Mode 03). The scanner will display any fault codes along with a brief description.
- Erase Codes (or Clear DTCs): This option clears stored DTCs and turns off the check engine light (Mode 04). Use this cautiously and only after understanding the cause of the codes.
- Live Data (or Data Stream, or Real-Time Data): This is the key option for reading live data parameters (Mode 01). Selecting this option will typically present you with a list of available PIDs or categories of data.
-
Reading Live Data (Mode 01):
- Select “Live Data” or the equivalent option on your scanner.
- You may be presented with a list of PIDs to choose from. You can select individual PIDs or pre-defined groups of parameters depending on your scanner.
- Select the PIDs you want to monitor (e.g., Engine RPM, Vehicle Speed, Coolant Temperature, etc.).
- The scanner will then display the real-time values of the selected PIDs, often updating several times per second.
Step 4: Understanding and Interpreting OBD2 Data
- DTCs: When you read DTCs from an OBD2 scanner, they are usually displayed with a code format like “P0123”. The first character indicates the system (P=Powertrain, C=Chassis, B=Body, U=Network). The following digits provide more specific information about the fault. You can use online OBD2 DTC lookup tools to get detailed descriptions of each code.
- Live Data (PIDs): Reading live data provides numerical values for various parameters. To understand these values, you need to know the units and scaling factors for each PID. For example, vehicle speed (PID 0D) is typically in km/h or mph, and engine temperature is in degrees Celsius or Fahrenheit.
- OBD2 PID Overview Tools and DBC Files: Resources like the OBD2 PID overview tool and OBD2 DBC files can be invaluable for understanding and decoding OBD2 data. DBC files allow you to use CAN bus analysis software to automatically decode raw OBD2 data into human-readable values.
By following these steps, you can successfully read data from an OBD2 scanner and start to understand your vehicle’s diagnostic information.
Decoding Multi-Frame OBD2 Data
While many OBD2 parameters are transmitted in single CAN frames, some data, like the VIN or DTCs lists, may require multiple frames due to their size. This is handled by the ISO-TP (ISO 15765-2) transport protocol.
When reading data from an OBD2 scanner that involves multi-frame responses, the process is generally handled transparently by the scanner itself. However, understanding multi-frame communication is helpful for advanced users or when working with raw OBD2 data logs.
For example, retrieving the VIN (Mode 09, PID 02) involves a multi-frame response. The scanner sends a request, and the vehicle responds with a series of CAN frames that, when reassembled, contain the complete VIN string.
Specialized CAN bus tools and software are needed to manually decode multi-frame OBD2 responses if you are working with raw data logs. Tools like the CANedge MF4 decoders are designed to handle ISO-TP and decode multi-frame OBD2 messages.
Practical Applications of Reading OBD2 Data
Reading data from an OBD2 scanner has numerous practical applications for vehicle owners and professionals alike:
- Vehicle Diagnostics and Repair: As discussed, OBD2 scanners are essential for diagnosing check engine lights and other vehicle problems. Reading DTCs and live data helps pinpoint the source of issues, guiding repairs.
- Performance Monitoring and Tuning: Car enthusiasts and tuners use OBD2 scanners to monitor engine performance parameters in real-time. This data is crucial for optimizing engine tuning, tracking performance improvements, and identifying potential bottlenecks.
- Fuel Efficiency and Driving Habits: By reading OBD2 data, you can monitor fuel consumption, driving speed, and engine load. This information can help you optimize your driving habits to improve fuel efficiency and reduce fuel costs.
- Predictive Maintenance: Continuously reading and logging OBD2 data can help identify trends and anomalies that may indicate developing problems. This enables proactive maintenance, preventing breakdowns and extending vehicle lifespan.
- Fleet Management and Telematics: OBD2 data loggers and telematics devices are used in fleet management to track vehicle location, driver behavior, fuel consumption, and vehicle health. This data is invaluable for optimizing fleet operations, improving safety, and reducing costs.
- Vehicle Black Box Functionality: OBD2 loggers can act as “black boxes” for vehicles, recording data during trips. This data can be useful in accident reconstruction, insurance claims, and warranty disputes.
Conclusion
Learning how to read data from an OBD2 scanner is a valuable skill for anyone involved with vehicles. It provides direct access to your car’s self-diagnostic system, enabling you to understand its health, diagnose problems, and monitor performance. By understanding OBD2 modes, PIDs, and using an OBD2 scanner effectively, you can empower yourself with vehicle data and make informed decisions about maintenance, repair, and driving.
Explore our range of OBD2 scanners and tools to start reading data from your vehicle today!
Buy now Contact us
Recommended for you
OBD2 DATA LOGGER: EASILY LOG & CONVERT OBD2 DATA
CANEDGE2 – PRO CAN IoT LOGGER
[
