Decoding the Equation for OBD2 VIN Number: A Comprehensive Guide

As a car expert at carparteu.com, I understand the importance of vehicle diagnostics and data access. The On-Board Diagnostics II (OBD2) system is crucial for accessing this information, and understanding how to retrieve the Vehicle Identification Number (VIN) through OBD2 is a key skill for any automotive enthusiast or professional. This guide provides a detailed look into the world of OBD2 and VIN retrieval, expanding on the basics to provide you with expert-level knowledge.

Understanding OBD2: Your Car’s Diagnostic Center

OBD2 is essentially your car’s internal health monitoring system. It’s a standardized protocol that allows you to pull out diagnostic trouble codes (DTCs) and real-time data from your vehicle using an OBD2 connector.

You’ve likely seen OBD2 in action without even realizing it. That check engine light on your dashboard? That’s OBD2 signaling a problem. When you take your car to a mechanic, they use an OBD2 scanner to figure out what’s wrong.

They plug this scanner into the 16-pin OBD2 connector, usually found near the steering wheel. The scanner sends “OBD2 requests” to your car, and the car responds with “OBD2 responses.” These responses can include things like speed, fuel level, or those all-important Diagnostic Trouble Codes (DTCs), making it much quicker to diagnose and fix car problems.

Alt text: OBD2 system interface showing malfunction indicator light and diagnostic scan tool connected to vehicle.

OBD2 Compatibility: Is Your Car Included?

The good news is, if you own a relatively recent car that’s not electric, it almost certainly supports OBD2. Most of these also use the Controller Area Network (CAN) bus for communication. However, just because an older car has a 16-pin OBD2 connector doesn’t guarantee OBD2 support. You need to consider when and where the car was originally purchased to be sure.

For a quick check of OBD2 compliance based on location and year of purchase, refer to this helpful guide:

Alt text: OBD2 compliance chart by region and vehicle type, highlighting US and EU regulations.

A Brief History of OBD2: From Emissions to Everywhere

OBD2’s story begins in California. The California Air Resources Board (CARB) mandated OBD in all new cars from 1991 onwards, primarily for emission control.

The Society of Automotive Engineers (SAE) then stepped in to standardize OBD, creating uniform DTCs and the now-familiar OBD connector through SAE J1962. This standardization was a game-changer.

The OBD2 standard rollout was gradual but impactful:

1996: OBD2 became mandatory in the USA for cars and light trucks.
2001: The EU made OBD2 required for gasoline cars.
2003: The EU extended the requirement to diesel cars (EOBD).
2005: OBD2 became mandatory in the US for medium-duty vehicles.
2008: US cars were required to use ISO 15765-4 (CAN) as the foundation for OBD2 communication.
2010: Finally, OBD2 was mandated for heavy-duty vehicles in the US.

Alt text: OBD2 historical timeline highlighting its origins in emission control and evolution to broader vehicle diagnostics, linking to CAN bus.

Alt text: Timeline illustration of OBD2 history from inception to widespread adoption in vehicles.

Alt text: Visual representation of OBD3 and future OBD evolution, emphasizing remote diagnostics, cloud connectivity, and IoT integration.

The Future of OBD2: Trends and Transformations

OBD2 isn’t standing still. While its original purpose was emissions testing, its role is evolving.

One key trend is the challenge OBD2 faces with electric vehicles (EVs). Because EVs don’t have the same emission concerns, they aren’t required to support OBD2 in the traditional sense. In fact, most modern EVs don’t support standard OBD2 requests. Instead, they often use manufacturer-specific UDS communication, making it harder to access data unless you can reverse engineer their systems. There are some successful cases of reverse engineering for brands like Tesla, Hyundai/Kia, Nissan, and VW/Skoda, which offer a glimpse into EV data access.

To address the limitations of current OBD2, especially in data richness and communication protocols, newer standards like WWH-OBD (World Wide Harmonized OBD) and OBDonUDS (OBD on UDS) are emerging. These aim to improve OBD communication using the UDS protocol as a base.

Looking ahead, OBD3 envisions a future with telematics integrated into all cars. Imagine cars equipped with radio transponders that automatically transmit the Vehicle Identification Number (VIN) and DTCs wirelessly to a central server for emission checks. This would streamline emission testing but also raises privacy concerns. Devices capable of transmitting CAN or OBD2 data via WiFi/cellular already exist, like the CANedge2 and CANedge3, showcasing the feasibility of this concept.

However, the increasing use of OBD2 for third-party data access is also facing pushback from car manufacturers. Originally intended for repair shop servicing, OBD2 was not designed to be an open door for a data-driven economy. Some manufacturers are exploring ways to limit OBD2 functionality during driving, centralizing data collection instead. While framed as a security measure against car hacking, this move is viewed by many as a way for manufacturers to control valuable automotive data, potentially disrupting the market for third-party OBD2 services.

Alt text: Visual metaphor of OBD2 connector being removed from an electric vehicle, symbolizing restricted data access in EVs compared to traditional vehicles.

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OBD2 Standards: Laying the Foundation

Think of OBD2 as a language spoken over a phone line, where the phone line is the CAN bus. OBD2 is a higher-layer protocol, similar to J1939, CANopen, and NMEA 2000, all built upon the CAN bus foundation.

The OBD2 standards define everything from the physical OBD2 connector to the lower-layer communication protocols and OBD2 Parameter IDs (PIDs).

These standards can be organized using the 7-layer OSI model. Notice how both SAE and ISO standards are involved, reflecting the US (SAE) and EU (ISO) origins of OBD. Many standards are technically equivalent, like SAE J1979 and ISO 15031-5, or SAE J1962 and ISO 15031-3.

Alt text: OSI model diagram illustrating the relationship between OBD2 and CAN bus protocols, highlighting relevant ISO and SAE standards.

Alt text: OBD2 connector pinout diagram, Type A female socket, detailing pin assignments for various communication protocols.

The OBD2 Connector [SAE J1962]: Your Access Point

The 16-pin OBD2 connector, standardized under SAE J1962 / ISO 15031-3, is your physical gateway to vehicle data. This Data Link Connector (DLC) is designed for easy access.

Key things to know about the OBD2 connector:

It’s usually near the steering wheel, though sometimes hidden.
Pin 16 provides battery power, often even when the ignition is off.
The OBD2 pinout changes depending on the communication protocol used.
CAN bus is the most common lower-layer protocol, meaning pins 6 (CAN-H) and 14 (CAN-L) are typically active.

OBD2 Connector Types: A vs. B

You’ll encounter both Type A and Type B OBD2 connectors. Type A is standard in cars, while Type B is more common in medium and heavy-duty vehicles.

While both types have similar pinouts, Type B provides 24V power supply compared to Type A’s 12V. Baud rates can also differ, with cars typically at 500K and heavy-duty vehicles often at 250K (though 500K support is increasing).

Type B connectors have a distinguishing interrupted groove in the middle. A Type B OBD2 adapter cable will fit both Type A and B sockets, but a Type A adapter will not fit a Type B socket.

Alt text: Comparison diagram of OBD2 Connector Type A and Type B, highlighting differences in power supply (12V vs 24V) and application (cars vs trucks).

Alt text: Diagram emphasizing the relationship between OBD2 and CAN bus (ISO15765), illustrating CAN as the physical layer for OBD2 communication.

OBD2 and CAN bus [ISO 15765-4]: The Communication Channel

Since 2008, CAN bus (ISO 15765) has been the mandatory lower-layer protocol for OBD2 in US cars.

ISO 15765-4, also known as Diagnostics over CAN (DoCAN), specifies how CAN is used for OBD2. It sets rules for the physical, data link, and network layers:

CAN bit-rate must be 250K or 500K.
CAN IDs can be 11-bit or 29-bit.
Specific CAN IDs are reserved for OBD requests and responses.
Diagnostic CAN frame data length is fixed at 8 bytes.
OBD2 adapter cable length limit is 5 meters.

OBD2 CAN Identifiers (11-bit, 29-bit): Addressing Messages

OBD2 communication relies on request and response messages.

Most cars use 11-bit CAN IDs for OBD2. The ‘Functional Addressing’ ID 0x7DF is used to ask all OBD2-compatible ECUs if they have data for a requested parameter. ‘Physical Addressing’ requests to specific ECUs use CAN IDs 0x7E0-0x7E7, but are less common.

ECUs respond with 11-bit IDs in the range 0x7E8-0x7EF. The most common response ID is 0x7E8 (from the Engine Control Module, ECM), followed by 0x7E9 (from the Transmission Control Module, TCM).

Some vehicles, especially vans and medium/heavy-duty vehicles, use 29-bit CAN identifiers for OBD2. Here, the ‘Functional Addressing’ CAN ID is 0x18DB33F1. Responses use CAN IDs from 0x18DAF100 to 0x18DAF1FF, often 0x18DAF110 and 0x18DAF11E. This response ID is also represented as the J1939 PGN 0xDA00 (55808), which is reserved for ISO 15765-2 in the J1939-71 standard.

Alt text: Diagram illustrating OBD2 request and response frame structure, showing PID data and parameter flow.

Alt text: Conceptual diagram differentiating OBD2 CAN bus from proprietary OEM-specific CAN bus data, highlighting data accessibility differences.

OBD2 vs. Proprietary CAN Protocols: Two Worlds of Data

It’s crucial to understand that your car’s ECUs don’t rely on OBD2 for their core functions. Manufacturers use their own proprietary CAN protocols for vehicle operation. These protocols are often specific to the brand, model, and year. Without OEM documentation or reverse engineering, this data is typically inaccessible.

When you connect a CAN bus data logger to your OBD2 port, you might see this OEM-specific CAN data, often broadcast at high rates (1000-2000 frames/second). However, many newer cars have a gateway that blocks access to this data, allowing only OBD2 communication through the OBD2 connector.

In essence, OBD2 is an additional higher-layer protocol running alongside the OEM’s proprietary protocol.

Bit-rate and ID Validation: Ensuring Correct Communication

OBD2 can use two bit-rates (250K, 500K) and two CAN ID lengths (11-bit, 29-bit), creating four possible combinations. Modern cars commonly use 500K and 11-bit IDs, but tools should systematically verify this.

ISO 15765-4 recommends an initialization sequence to determine the correct combination. This method relies on the fact that OBD2-compliant vehicles must respond to a mandatory OBD2 request (PID 0x00 in mode 0x01) and that incorrect bit-rates cause CAN error frames.

Newer ISO 15765-4 versions account for OBD communication via OBDonUDS versus OBDonEDS. This article primarily focuses on OBD2/OBDonEDS (OBD on emission diagnostic service as per ISO 15031-5/SAE J1979) rather than WWH-OBD/OBDonUDS (OBD on Unified Diagnostic Service as per ISO 14229, ISO 27145-3/SAE J1979-2).

To test for OBDonEDS vs OBDonUDS, tools may send UDS requests with 11-bit/29-bit functional address IDs for service 0x22 and data identifier (DID) 0xF810 (protocol identification). OBDonUDS vehicles should respond to this DID. OBDonEDS (aka OBD2, SAE OBD, EOBD, ISO OBD) is prevalent in non-EV cars, while WWH-OBD is mainly in EU trucks/buses.

Alt text: Flowchart illustrating the process of OBD2 bit-rate and CAN ID validation according to ISO 15765-4 standards.

Alt text: Diagram showcasing the five lower-layer OBD2 protocols including CAN (ISO 15765), KWP2000, SAE J1850 (VPW & PWM), and ISO 9141, emphasizing protocol diversity.

Five Lower-Layer OBD2 Protocols: A Historical Perspective

While CAN (ISO 15765) dominates OBD2 today, especially in post-2008 vehicles, older cars used other lower-layer protocols. Knowing these can be helpful when working with older vehicles. Pinouts can sometimes indicate the protocol in use:

ISO 15765 (CAN bus): Mandatory in US cars since 2008, widely used today.
ISO14230-4 (KWP2000): Common in 2003+ Asian cars.
ISO 9141-2: Used in EU, Chrysler, and Asian cars around 2000-2004.
SAE J1850 (VPW): Primarily in older GM cars.
SAE J1850 (PWM): Primarily in older Ford cars.

Transporting OBD2 Messages via ISO-TP [ISO 15765-2]: Handling Larger Data

OBD2 data is transmitted over CAN using ISO-TP (ISO 15765-2), a transport protocol that enables payloads larger than 8 bytes. This is essential for OBD2 functions like retrieving the Vehicle Identification Number (VIN) or Diagnostic Trouble Codes (DTCs). ISO 15765-2 handles segmentation, flow control, and reassembly of these larger messages.

For simpler OBD2 data that fits within a single CAN frame, ISO 15765-2 specifies ‘Single Frame’ (SF) usage. The first data byte (PCI field) indicates the payload length (excluding padding), leaving 7 bytes for OBD2 communication.

Alt text: Illustration of ISO 15765-2 (ISO-TP) frame types used in OBD2 communication, including Single Frame, First Frame, Consecutive Frame, and Flow Control Frame.

The OBD2 Diagnostic Message [SAE J1979, ISO 15031-5]: Anatomy of a Request

Let’s dissect a raw ‘Single Frame’ OBD2 CAN message to understand its structure. Simplified, it includes an identifier, data length (PCI field), and data. The data portion is further broken down into Mode, Parameter ID (PID), and data bytes.

Alt text: Diagram breaking down the structure of an OBD2 message, illustrating the arrangement of Mode, PID, Identifier, and Data bytes within a frame.

Example: OBD2 Request/Response for Vehicle Speed

Consider a request for ‘Vehicle Speed’. An external tool sends a request to the car with CAN ID 0x7DF, containing two payload bytes: Mode 0x01 and PID 0x0D. The car responds via CAN ID 0x7E8 with three payload bytes, including the speed value in the 4th byte, 0x32 (decimal 50).

Using OBD2 PID decoding rules, we find that 0x32 corresponds to 50 km/h. This example demonstrates the basic request-response interaction in OBD2.

Alt text: Example of OBD2 request (ID 7DF) and response (ID 7E8) messages for vehicle speed, illustrating data flow.

Alt text: Detailed example of OBD2 PID 0D for vehicle speed, showing request and response byte values and interpretation.

Alt text: Overview of the 10 OBD2 service modes, including descriptions for current data, freeze frame, and DTC clearing services.

The 10 OBD2 Services (Modes): Diagnostic Functions

There are 10 standardized OBD2 diagnostic services, or modes. Mode 0x01 provides real-time data, while others handle DTCs, freeze frame data, and more.

Vehicles don’t need to support all OBD2 modes, and they can also have manufacturer-specific modes beyond these 10.

In OBD2 messages, the mode is the 2nd byte. Requests use the mode value directly (e.g., 0x01), while responses add 0x40 to the mode value (e.g., 0x41).

OBD2 Parameter IDs (PIDs): Accessing Specific Data

Each OBD2 mode contains Parameter IDs (PIDs). For example, mode 0x01 has around 200 standardized PIDs for real-time data like speed, RPM, and fuel level. However, vehicles usually support only a subset of these PIDs.

One PID stands out: mode 0x01 PID 0x00. If an emissions-related ECU supports any OBD2 services, it must support this PID. Responding to PID 0x00, the ECU indicates support for PIDs 0x01-0x20. This makes PID 0x00 a fundamental OBD2 compatibility test. Similarly, PIDs 0x20, 0x40, etc., determine support for other mode 0x01 PID ranges.

Alt text: Reiteration of OBD2 request and response frame structure, emphasizing PID data and parameter handling.

Alt text: Screenshot of an OBD2 PID overview tool interface, displaying service 01 parameters and data.

Tip: OBD2 PID Overview Tool for Easy Lookup

SAE J1979 and ISO 15031-5 appendices detail scaling information for standard OBD2 PIDs, enabling data decoding into physical values.

Our OBD2 PID overview tool simplifies looking up mode 0x01 PIDs. It helps you create OBD2 requests and dynamically decode responses.

OBD2 PID overview tool

How to Log and Decode OBD2 Data: A Practical Guide

Let’s walk through logging OBD2 data using the CANedge CAN bus data logger as a practical example. The CANedge allows custom CAN frame transmission, making it ideal for OBD2 logging. Connect it to your vehicle with an OBD2-DB9 adapter cable.

Alt text: Diagram showing an OBD2 PID data logger setup, illustrating request and response flow with CAN IDs 7DF and 7E8.

You can send a CAN frame at e.g. 500K, then check if it is successfully sent

The responses to ‘Supported PIDs’ can be reviewed in asammdf

Alt text: OBD2 PID lookup tool interface showing supported PIDs, aiding in decoding and interpretation of diagnostic data.

Step #1: Verify Bit-rate, IDs & Supported PIDs

ISO 15765-4 outlines how to determine the correct bit-rate and IDs for a vehicle. Use the CANedge to test this:

Send a CAN frame at 500K; check for success (if not, try 250K).
Use the confirmed bit-rate for all further communication.
Send ‘Supported PIDs’ requests and analyze the responses.
Response IDs will indicate 11-bit or 29-bit IDs.
Response data reveals supported PIDs.

We offer plug-and-play configurations for these tests. Most post-2008 non-EV cars support 40-80 PIDs using 500K bit-rate, 11-bit CAN IDs, and the OBD2/OBDonEDS protocol.

As seen in the asammdf GUI screenshot, a single OBD request often triggers multiple responses. This is because the 0x7DF request ID polls all ECUs. Since all OBD2/OBDonEDS ECUs must support service 0x01 PID 0x00, many responses to this PID are common. Subsequent ‘Supported PIDs’ requests get fewer responses. Notice that the ECM ECU (0x7E8) supports all PIDs supported by other ECUs in this example. To reduce busload, switch to ‘Physical Addressing’ with CAN ID 0x7E0 to target only the ECM for subsequent requests.

Step #2: Configure OBD2 PID Requests for Logging

Once you know your vehicle’s supported PIDs, bit-rate, and CAN IDs, configure your transmit list with the PIDs you want to log.

Consider these points:

CAN IDs: Use ‘Physical Addressing’ request IDs (e.g., 0x7E0) to avoid multiple responses.
Spacing: Add 300-500 ms between OBD2 requests to prevent ECU overload.
Battery drain: Use triggers to stop transmissions when the vehicle is off.
Filters: Filter to record only OBD2 responses if OEM-specific CAN data is also present.

With these settings, your CANedge is ready to log raw OBD2 data.

An example list of CANedge OBD2 PID requests

asammdf lets you DBC decode and visualize OBD2 data

Step #3: DBC Decode Raw OBD2 Data for Analysis

To analyze and visualize your logged data, decode the raw OBD2 data into physical values (km/h, °C, etc.).

Decoding information is in ISO 15031-5/SAE J1979 (and online resources like Wikipedia). We provide a free OBD2 DBC file for easy DBC decoding in most CAN bus software tools.

Decoding OBD2 data is slightly more complex than standard CAN signals because different OBD2 PIDs use the same CAN ID (e.g., 0x7E8). The CAN ID alone isn’t enough to identify the payload signals.

You need to use the CAN ID, OBD2 mode, and OBD2 PID together to identify signals. This is ‘extended multiplexing,’ which DBC files can handle.

CANedge: Your OBD2 Data Logging Solution

The CANedge simplifies OBD2 data recording to an 8-32 GB SD card. Connect it to your car or truck to start logging, and use free software/APIs and our OBD2 DBC file for decoding.

OBD2 logger intro CANedge

OBD2 Multi-Frame Examples [ISO-TP]: VIN Retrieval and More

OBD2 communication uses ISO-TP (ISO 15765-2) for all data, including multi-frame messages. Most examples so far have been single-frame. Multi-frame communication requires flow control frames. Often, a static flow control frame is sent ~50 ms after the initial request, as shown in the CANedge configuration.

Multi-frame OBD2 responses require CAN software/API tools that support ISO-TP, like CANedge MF4 decoders.

Alt text: Example of an OBD2 multi-frame request message for Vehicle Identification Number (VIN) retrieval, showcasing ISO-TP communication.

Example 1: OBD2 Vehicle Identification Number (VIN) Retrieval

The Vehicle Identification Number (VIN) is essential for telematics and diagnostics. To retrieve the VIN via OBD2, use mode 0x09 and PID 0x02. This process effectively embodies the Equation For Obd2 Vin Number retrieval: a specific request initiates a multi-frame response containing the VIN.

The tester tool sends a Single Frame request with PCI field (0x02), service identifier (0x09), and PID (0x02). The vehicle responds with a First Frame containing PCI, length (0x014 = 20 bytes), mode (0x49), and PID (0x02). Byte 0x01 after the PID is the Number Of Data Items (NODI), in this case 1. The following 17 bytes are the VIN, convertible from HEX to ASCII.

Example 2: OBD2 Multi-PID Request (6x) – Advanced Data Acquisition

OBD2 allows requesting up to 6 mode 0x01 PIDs in a single request frame. The ECU responds with data for supported PIDs (skipping unsupported ones), potentially using multi-frame responses.

This boosts data collection speed but makes signal encoding request-specific, complicating generic OBD2 DBC file use. It’s generally not recommended for practical use.

The multi-frame response is similar to the VIN example, but the payload includes requested PIDs and their data. PIDs are often ordered as requested, but the ISO 15031-5 standard doesn’t strictly require this.

Decoding these responses with DBC files is challenging. It involves complex extended multiplexing, requiring DBC files to account for PID payload positions, which varies across vehicles. For complex multi-PID requests, consider custom scripts that interpret responses in context with requests, though these are hard to scale.

Example 3: OBD2 Diagnostic Trouble Codes (DTCs) – Identifying Problems

Mode 0x03 (‘Show stored Diagnostic Trouble Codes’) retrieves emissions-related DTCs. No PID is needed in the request. ECUs respond with the number of stored DTCs (possibly zero), with each DTC being 2 bytes. Multi-frame responses are needed for more than 2 DTCs.

The 2-byte DTC value is categorized by the first 2 bits, with the remaining 14 bits forming a 4-digit hexadecimal code. Decoded DTCs can be looked up using OBD2 DTC lookup tools like repairpal.com.

Alt text: OBD2 DTC decoding example, illustrating the structure of a DTC code and its interpretation for diagnostic purposes.

The example shows a request to an ECU with 6 stored DTCs, demonstrating multi-frame communication for a larger diagnostic data set.

OBD2 Data Logging: Real-World Applications

OBD2 data from cars and light trucks has diverse applications:

Alt text: OBD2 data logger connected to a car, symbolizing on-board diagnostics and data acquisition.

Logging Data from Cars for Various Purposes

OBD2 data logging in cars can be used for fuel efficiency improvements, driving behavior analysis, prototype testing, and insurance telematics.

obd2 logger

Alt text: OBD2 real-time streaming diagnostics setup, indicating USB interface and live data monitoring.

Real-Time Car Diagnostics for Immediate Insights

OBD2 interfaces enable real-time streaming of human-readable OBD2 data, aiding in immediate vehicle issue diagnosis.

obd2 streaming

Alt text: OBD2 data logger used for predictive maintenance, illustrating telematics and IoT integration for vehicle health monitoring.

Predictive Maintenance: Anticipating Vehicle Needs

IoT OBD2 loggers allow cloud-based vehicle monitoring to predict and prevent breakdowns, enhancing vehicle uptime.

predictive maintenance

Alt text: CAN bus data logger as a vehicle black box, implying data recording for insurance, warranty, and accident analysis.

Vehicle Blackbox Logging for Accountability

An OBD2 logger acts as a ‘blackbox’ for vehicles, providing crucial data for dispute resolution and diagnostic insights in various scenarios.

can bus blackbox

Have an OBD2 data logging application in mind? Contact us for expert consultation and guidance!

Explore our guides section for more introductory content, or download the comprehensive ‘Ultimate Guide’ PDF.

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