Decoding OBD2 Types: A Comprehensive Guide for Automotive Diagnostics

The On-Board Diagnostic system, more commonly known as OBD2, is an essential feature in modern vehicles. As a standardized protocol, OBD2 allows mechanics and car enthusiasts to access a wealth of information about a vehicle’s health and performance. This guide will delve into the world of OBD2, exploring the various Obd2 Types, connectors, protocols, and parameters that make it such a powerful diagnostic tool. Whether you’re a seasoned mechanic or just curious about your car’s inner workings, understanding obd2 types is crucial.

You may have already encountered OBD2 when that check engine light illuminated on your dashboard. This is your vehicle signaling a potential issue, and OBD2 is the key to understanding what’s wrong. Mechanics use OBD2 scanners to interface with your car’s computer via the standardized OBD2 16-pin connector, typically located near the steering wheel. These scanners send requests and receive responses containing valuable data like speed, engine temperature, and those all-important Diagnostic Trouble Codes (DTCs). This data enables faster and more accurate troubleshooting.

Does Your Vehicle Utilize OBD2 Types?

The likelihood is high if you own a relatively recent non-electric car. OBD2 has become a near-universal standard for vehicles across the globe. However, simply having a 16-pin connector doesn’t guarantee OBD2 compliance, especially in older models. Some older vehicles may feature the connector without fully supporting the OBD2 protocol. A key indicator of OBD2 compliance is the vehicle’s purchase location and year:

A Brief History of OBD2 Types and Standards

The origins of OBD2 can be traced back to California, where the California Air Resources Board (CARB) mandated on-board diagnostics in all new cars from 1991 onwards, primarily for emission control.

The Society of Automotive Engineers (SAE) played a crucial role in standardizing OBD2, leading to uniform DTCs and the standardized OBD connector, as outlined in SAE J1962. This standardization was critical in defining the different obd2 types and ensuring interoperability across manufacturers.

The adoption of OBD2 was a gradual process:

1996: OBD2 becomes mandatory in the USA for cars and light trucks.
2001: The EU mandates OBD2 for gasoline cars (EOBD).
2003: EOBD is extended to diesel cars in the EU.
2005: OBD2 becomes required for medium-duty vehicles in the US.
2008: US vehicles are required to use ISO 15765-4 (CAN) as the foundation for OBD2 communication, standardizing one of the key obd2 types in terms of communication protocols.
2010: OBD2 is mandated for heavy-duty vehicles in the US.

The Future Landscape of OBD2 Types

While OBD2 remains a cornerstone of vehicle diagnostics, its future is evolving. Here are some key trends shaping the future of obd2 types:

Initially designed for emission control, legislated OBD2 isn’t strictly required for electric vehicles (EVs). Consequently, many modern EVs don’t support standard OBD2 requests, opting instead for OEM-specific UDS communication. This makes accessing data from EVs challenging without specialized knowledge or reverse engineering efforts, as seen in case studies for Tesla, Hyundai/Kia, Nissan, and VW/Skoda EVs.

Recognizing the limitations of current OBD2 implementations in terms of data richness and lower-layer protocols, alternatives like WWH-OBD (World Wide Harmonized OBD) and OBDonUDS (OBD on UDS) are emerging. These protocols aim to improve OBD communication by using the UDS protocol as a base. These represent a new generation of obd2 types, focusing on enhanced communication capabilities.

In an increasingly connected world, manual emission checks via OBD2 seem outdated. OBD3 proposes a solution by integrating telematics into all cars. This involves adding a radio transponder to vehicles, allowing for wireless transmission of the Vehicle Identification Number (VIN) and DTCs to a central server for automated checks.

While devices like the CANedge2 WiFi CAN logger and CANedge3 3G/4G CAN logger already facilitate wireless OBD2 data transfer, OBD3 faces political hurdles due to surveillance concerns.

The original purpose of OBD2 was for diagnostics in repair shops. However, third-party use of OBD2 for real-time data generation via OBD2 dongles and CAN loggers is now widespread. The German car industry, however, is pushing to limit this third-party access, arguing that OBD2 was never intended to fuel a data-driven economy.

The proposal is to disable OBD2 functionality during driving and centralize data collection with manufacturers. This would give manufacturers control over automotive big data, raising concerns about market disruption for third-party OBD2 services and potentially impacting the future of obd2 types accessible to consumers and independent services. Security concerns, such as car hacking risks, are cited as a justification, although many view this as a commercially motivated move.

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Understanding OBD2 Standards and Types

On-board diagnostics, OBD2, operates as a higher-layer protocol, similar to a language, built upon communication methods like CAN bus. This places OBD2 alongside other CAN-based higher-layer protocols such as J1939, CANopen, and NMEA 2000.

OBD2 standards meticulously define various aspects, including the OBD2 connector, lower-layer protocols, and OBD2 Parameter IDs (PIDs). These standards are crucial in differentiating obd2 types based on their underlying communication methods.

The standards can be categorized within a 7-layer OSI model. Notably, both SAE (primarily US standards) and ISO (international standards often adopted in the EU) contribute to defining these layers. Many SAE and ISO standards are technically equivalent, such as SAE J1979 and ISO 15031-5, or SAE J1962 and ISO 15031-3.

The OBD2 Connector: SAE J1962 and Connector Types

The 16-pin OBD2 connector, specified in SAE J1962 / ISO 15031-3, provides a standardized interface for accessing vehicle data. This connector is a key element when discussing obd2 types as it is the physical interface through which diagnostic communication occurs.

The illustration shows a Type A OBD2 pin connector, also known as the Data Link Connector (DLC). Key points to note:

The connector is typically located near the steering wheel, but its exact location can vary and may be hidden.
Pin 16 provides battery power, often even when the ignition is off.
The OBD2 pinout configuration depends on the communication protocol used by the vehicle, further defining obd2 types based on protocol.
CAN bus is the most prevalent lower-layer protocol, meaning pins 6 (CAN-H) and 14 (CAN-L) are commonly connected.

OBD2 Connector Types: A vs. B

You’ll commonly encounter two main obd2 connector types: Type A and Type B. Type A is standard in cars, while Type B is more prevalent in medium and heavy-duty vehicles.

While both types share similar OBD2 pinouts, they differ in power supply outputs: Type A provides 12V, and Type B provides 24V. Baud rates often differ as well, with cars typically using 500K, while heavy-duty vehicles often use 250K (with increasing support for 500K).

Visually distinguishing them, Type B connectors have an interrupted groove in the middle. Consequently, a Type B OBD2 adapter cable is compatible with both Type A and Type B sockets, whereas a Type A adapter will not fit into a Type B socket. Understanding these obd2 connector types is important for selecting the correct diagnostic equipment.

OBD2 and CAN Bus: ISO 15765-4 and Protocol Types

Since 2008, CAN bus has been the mandatory lower-layer protocol for OBD2 in all US-sold vehicles, as per ISO 15765. This standardization of communication protocol is a critical aspect of obd2 types.

ISO 15765-4, also known as Diagnostics over CAN (DoCAN), outlines specific constraints applied to the CAN standard (ISO 11898) for OBD2 applications. It standardizes the CAN interface for diagnostic equipment, focusing on the physical, data link, and network layers:

CAN bus bit-rate must be either 250K or 500K.
CAN IDs can be 11-bit or 29-bit.
Specific CAN IDs are designated for OBD requests and responses, defining communication obd2 types.
Diagnostic CAN frame data length is fixed at 8 bytes.
The OBD2 adapter cable length must not exceed 5 meters.

OBD2 CAN Identifiers: 11-bit and 29-bit Types

OBD2 communication relies on request/response message exchanges. The CAN identifier used is another way to categorize obd2 types.

In most passenger cars, 11-bit CAN IDs are used for OBD2. The ‘Functional Addressing’ ID is 0x7DF, which is a broadcast request to all OBD2-compatible ECUs. ‘Physical Addressing’ requests to specific ECUs use CAN IDs 0x7E0-0x7E7, though these are less common.

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

Some vehicles, particularly vans and medium/heavy-duty vehicles, may employ extended 29-bit CAN identifiers for OBD2 communication.

Here, the ‘Functional Addressing’ CAN ID is 0x18DB33F1.

Responses in 29-bit implementations use CAN IDs ranging from 0x18DAF100 to 0x18DAF1FF, typically 18DAF110 and 18DAF11E. These response IDs are sometimes presented in the J1939 PGN format, specifically PGN 0xDA00 (55808), which is reserved for ISO 15765-2 in the J1939-71 standard.

OBD2 vs. Proprietary CAN Protocols: Differentiating Data Types

It’s important to understand that vehicle Electronic Control Units (ECUs) operate using OEM-specific proprietary CAN protocols, independent of OBD2. These protocols are tailored to the vehicle brand, model, and year. Interpreting this OEM-specific data is generally not possible without OEM tools or reverse engineering. This distinction highlights different data types available via the CAN bus in vehicles.

Connecting a CAN bus data logger to the OBD2 connector may capture OEM-specific CAN data, often broadcast at high rates (1000-2000 frames/second). However, many newer vehicles utilize a gateway that restricts access to this OEM data, allowing only OBD2 communication through the OBD2 connector.

Think of OBD2 as an additional, higher-layer protocol operating alongside the OEM-specific protocol. This means there are fundamentally two types of CAN data you might encounter: standardized OBD2 and proprietary OEM data.

Bit-rate and ID Validation for OBD2 Protocol Types

As mentioned, OBD2 can utilize two bit-rates (250K, 500K) and two CAN ID lengths (11-bit, 29-bit), resulting in four potential combinations of obd2 protocol types. Modern cars commonly use 500K and 11-bit IDs, but diagnostic tools should systematically verify this.

ISO 15765-4 provides a standardized initialization sequence to determine the correct combination. This method leverages the mandatory support for a specific OBD2 request (see OBD2 PID section) and the detection of CAN error frames caused by incorrect bit-rate transmissions.

Newer versions of ISO 15765-4 accommodate vehicles supporting OBD communication via OBDonUDS in addition to OBDonEDS. This article primarily focuses on OBD2/OBDonEDS (OBD on Emission Diagnostic Service as per ISO 15031-5/SAE J1979) versus WWH-OBD/OBDonUDS (OBD on Unified Diagnostic Service as per ISO 14229, ISO 27145-3/SAE J1979-2).

To distinguish between OBDonEDS and OBDonUDS, test tools may send UDS requests with 11-bit/29-bit functional address IDs for service 0x22 and data identifier (DID) 0xF810 (protocol identification). Vehicles supporting OBDonUDS must respond to this DID.

In practice, OBDonEDS (also known as OBD2, SAE OBD, EOBD, or ISO OBD) is prevalent in most non-EV cars, while WWH-OBD is mainly used in EU trucks and buses, representing different implementation types of OBD.

Five Lower-Layer OBD2 Protocol Types

While CAN (ISO 15765) is the dominant lower-layer protocol for OBD2 today, particularly in vehicles post-2008, older cars may utilize other protocols. Understanding these legacy obd2 protocol types is useful when working with older vehicles. Pinouts can help identify the protocol in use:

ISO 15765 (CAN bus): Mandatory in US cars since 2008 and widely used today.
ISO14230-4 (KWP2000): Keyword Protocol 2000, common in 2003+ cars, particularly in Asia.
ISO 9141-2: Used in EU, Chrysler, and Asian cars in the 2000-2004 era.
SAE J1850 (VPW): Predominantly used in older GM vehicles.
SAE J1850 (PWM): Primarily used in older Ford vehicles.

ISO-TP: Transporting OBD2 Messages (ISO 15765-2)

OBD2 data transmission over CAN bus relies on the ISO-TP transport protocol (ISO 15765-2). This protocol enables the transmission of data payloads exceeding the 8-byte CAN frame limit. ISO-TP is crucial for OBD2 functions like retrieving the Vehicle Identification Number (VIN) or Diagnostic Trouble Codes (DTCs). It manages segmentation, flow control, and reassembly of larger messages.

For smaller OBD2 data transmissions that fit within a single CAN frame, ISO 15765-2 defines the ‘Single Frame’ (SF) format. In SF, the first data byte (PCI field) indicates the payload length (excluding padding), leaving 7 bytes for OBD2 communication. This highlights different obd2 message types based on payload size and ISO-TP usage.

The OBD2 Diagnostic Message: SAE J1979, ISO 15031-5 and Message Types

To understand OBD2 communication over CAN, let’s examine a simplified ‘Single Frame’ OBD2 CAN message structure. An OBD2 message consists of an identifier, a data length indicator (PCI field), and the data payload itself. The data payload is further structured into Mode, Parameter ID (PID), and data bytes. These components define the fundamental obd2 message types.

OBD2 Request/Response Example: A Message Type Illustration

Consider a request for ‘Vehicle Speed’ as an example.

A diagnostic tool sends a request message to the vehicle with CAN ID 0x7DF, containing two payload bytes: Mode 0x01 and PID 0x0D. The vehicle responds with CAN ID 0x7E8 and a 3-byte payload, where the 4th byte, 0x32 (decimal 50), represents the Vehicle Speed value.

Using OBD2 PID decoding rules, we can determine that 0x32 corresponds to 50 km/h, illustrating how obd2 message types are used to request and receive specific data.

The 10 OBD2 Services (Modes): Functional Types

OBD2 defines 10 diagnostic services, also referred to as modes. These modes represent different functional types of diagnostic operations. Mode 0x01 provides real-time data, while others handle Diagnostic Trouble Codes (DTCs), freeze frame data, and more.

Vehicles are not required to support all 10 OBD2 modes and may also implement OEM-specific modes beyond the standard set.

In OBD2 messages, the mode is indicated in the second byte. In a request message, the mode is included directly (e.g., 0x01). In a response, 0x40 is added to the requested mode (e.g., 0x41).

OBD2 Parameter IDs (PIDs): Data Point Types

Within each OBD2 mode, Parameter IDs (PIDs) identify specific data points. Mode 0x01, for instance, contains approximately 200 standardized PIDs providing real-time data like speed, RPM, and fuel level. However, vehicles typically support only a subset of the PIDs defined within each mode. PIDs represent different data types accessible through OBD2.

One PID holds special significance: Mode 0x01 PID 0x00. If an emissions-related ECU supports any OBD2 services, it must support mode 0x01 PID 0x00. Responding to this PID, the ECU indicates its support for PIDs 0x01-0x20. This makes PID 0x00 a fundamental test for OBD2 compatibility. PIDs 0x20, 0x40, and so on, similarly indicate support for subsequent PID ranges within mode 0x01.

Tip: Utilizing an OBD2 PID Overview Tool

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

For quick lookup of mode 0x01 PIDs, utilize an OBD2 PID overview tool. This tool aids in constructing OBD2 request frames and dynamically decoding OBD2 responses, simplifying the process of understanding different obd2 data types.

OBD2 PID overview tool

Practical OBD2 Data Logging and Decoding

This section illustrates a practical example of logging OBD2 data using the CANedge CAN bus data logger.

The CANedge allows configuration of custom CAN frame transmissions, making it suitable for OBD2 logging.

Connecting the CANedge to your vehicle via an OBD2-DB9 adapter cable enables easy data acquisition.

Review responses to ‘Supported PIDs’ in asammdf

Step #1: Bit-rate, ID, and Supported PID Validation for Protocol Type Discovery

ISO 15765-4 outlines the process for identifying the bit-rate and IDs used by a vehicle. The CANedge can be used to test this:

Transmit a CAN frame at 500K and check for successful transmission (if unsuccessful, try 250K).
Use the identified bit-rate for subsequent communication.
Send multiple ‘Supported PIDs’ requests and analyze the responses.
Response IDs indicate 11-bit or 29-bit CAN ID usage, identifying obd2 protocol types.
Response data reveals supported PIDs, showing available obd2 data types.

Pre-configured settings are available for these tests.

Most post-2008 non-EV cars support 40-80 PIDs using a 500K bit-rate, 11-bit CAN IDs, and the OBD2/OBDonEDS protocol.

As seen in the asammdf GUI example, multiple responses to a single OBD request are common due to the use of the 0x7DF request ID, which polls all ECUs. Since all OBD2/OBDonEDS-compliant ECUs must support service 0x01 PID 0x00, numerous responses to this PID are typical. Fewer ECUs respond to subsequent ‘Supported PIDs’ requests. The ECM ECU (0x7E8) often supports all PIDs supported by other ECUs in the example, suggesting that using ‘Physical Addressing’ CAN ID 0x7E0 for subsequent communication could reduce bus load.

Step #2: Configuring OBD2 PID Requests for Desired Data Types

Once you’ve determined the supported OBD2 PIDs, bit-rate, and CAN IDs for your vehicle, configure your transmit list with the PIDs of interest, focusing on specific obd2 data types.

Consider these factors:

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

With these configurations, the CANedge is ready to log raw OBD2 data.

Example CANedge OBD2 PID request list

Visualize DBC decoded OBD2 data in asammdf

Step #3: DBC Decoding of Raw OBD2 Data for Usable Data Types

To analyze and visualize logged data, decode the raw OBD2 data into physical values (e.g., km/h, °C). This process reveals the practical obd2 data types in human-readable form.

Decoding information is found in ISO 15031-5/SAE J1979 and online resources like Wikipedia. A free OBD2 DBC file is available to simplify DBC decoding in CAN bus software tools.

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

Signal identification requires using the CAN ID, OBD2 mode, and OBD2 PID. This ‘extended multiplexing’ technique can be implemented in DBC files, allowing software to correctly interpret the different obd2 data types.

CANedge: Your OBD2 Data Logger

The CANedge facilitates easy OBD2 data recording to an 8-32 GB SD card. Simply connect it to a vehicle to start logging and decode data using free software/APIs and our OBD2 DBC file.

OBD2 logger intro CANedge

OBD2 Multi-Frame Examples: ISO-TP in Action

OBD2 communication relies on ISO-TP (ISO 15765-2) for all data exchange. While previous examples focused on single-frame communication, multi-frame communication is essential for larger data sets. These examples further illustrate different obd2 message types and their handling.

Multi-frame OBD2 communication necessitates flow control frames. A static flow control frame transmitted approximately 50 ms after the initial request frame is a common practice, as shown in the CANedge configuration example.

Software tools with ISO-TP support, like CANedge MF4 decoders, are required to process multi-frame OBD2 responses.

Example 1: Retrieving the OBD2 Vehicle Identification Number (VIN)

The Vehicle Identification Number (VIN) is crucial for telematics and diagnostics. OBD2 mode 0x09 PID 0x02 is used to request the VIN:

The diagnostic tool sends a Single Frame request containing the PCI field (0x02), request service identifier (0x09), and PID (0x02).

The vehicle responds with a First Frame containing the PCI, length (0x014 = 20 bytes), mode (0x49, i.e., 0x09 + 0x40), and PID (0x02). Following the PID is the Number Of Data Items (NODI) byte (0x01 in this case). The remaining 17 bytes represent the VIN, which can be converted from HEX to ASCII.

Example 2: OBD2 Multi-PID Request (6x) – An Advanced Message Type

OBD2 allows requesting up to 6 mode 0x01 PIDs in a single request frame. The ECU responds with data for supported PIDs, potentially using multi-frame responses. This method increases data collection efficiency but complicates signal encoding and generic DBC file usage. It represents a more complex obd2 message type for advanced applications.

While powerful, this approach is not generally recommended for practical data logging due to decoding complexity. Here’s an example trace:

The multi-frame response is similar to the VIN example but includes requested PIDs and their corresponding data. PIDs are often ordered as requested, but this is not mandatory.

Decoding these responses using generic DBC files is challenging. This method creates a complex extended multiplexing scenario, making it difficult to generalize DBC files across different vehicles. It’s best suited for tools with specific built-in support for multi-PID requests.

Example 3: Accessing OBD2 Diagnostic Trouble Codes (DTCs) – Error Message Types

OBD2 mode 0x03, ‘Show stored Diagnostic Trouble Codes,’ retrieves emissions-related DTCs. No PID is included in the request. The ECU responds with the number of stored DTCs (potentially zero) and the DTCs themselves, with each DTC occupying 2 data bytes. Multi-frame responses are necessary if more than two DTCs are stored. DTCs represent specific error message types within OBD2.

The 2-byte DTC value is divided into category bits and a 4-digit hexadecimal code. Decoded DTC values can be looked up using OBD2 DTC lookup tools like repairpal.com.

The example below shows a request to an ECU with 6 stored DTCs.

OBD2 Data Logging: Use Case Examples Across OBD2 Types

OBD2 data from cars and light trucks has diverse applications across various obd2 types of vehicles and industries:

Car Data Logging: Performance and Efficiency Analysis

OBD2 data logging in cars can be used to optimize fuel consumption, improve driving habits, test prototype components, and for insurance telematics applications.

obd2 logger

Real-time Car Diagnostics: Immediate Issue Detection

OBD2 interfaces facilitate real-time streaming of human-readable OBD2 data, enabling immediate diagnosis of vehicle issues and faster repair processes.

obd2 streaming

Predictive Maintenance: Proactive Vehicle Health Monitoring

IoT OBD2 loggers enable cloud-based monitoring of cars and light trucks for predictive maintenance, helping to anticipate and prevent breakdowns, reducing downtime and repair costs.

predictive maintenance

Vehicle Black Box Logging: Incident and Warranty Data

An OBD2 logger can function as a ‘black box’ for vehicles or equipment, recording crucial data for incident analysis, warranty claims, and in-depth diagnostics after events.

can bus blackbox

Do you have an OBD2 data logging application in mind? Contact us for expert consultation!

Explore our guides section for more introductory resources or download the comprehensive ‘Ultimate Guide’ PDF for in-depth knowledge.

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