Chevrolet OBD2 Protocol: Your Comprehensive Guide to On-Board Diagnostics

Are you a Chevrolet owner looking to understand your vehicle’s diagnostic system? This guide provides a practical introduction to the On-Board Diagnostic (OBD2) protocol, specifically for Chevrolet vehicles. We’ll explore the OBD2 connector, OBD2 parameter IDs (PIDs), and how it links to the CAN bus system in your Chevy.

This is a hands-on introduction, designed to teach you how to request and decode OBD2 data, understand key logging applications, and offer practical tips for working with your Chevrolet’s OBD2 system.

Discover why this is becoming a go-to resource for understanding the OBD2 system in Chevrolet vehicles.

You can also watch our OBD2 intro video above – or get the PDF

Understanding OBD2 in Your Chevrolet

OBD2 is essentially your Chevrolet’s internal health monitoring system. It’s a standardized protocol that allows you to retrieve diagnostic trouble codes (DTCs) and access real-time vehicle data through the OBD2 connector.

You’ve likely encountered OBD2 without realizing it:

Have you ever seen the “check engine light” illuminate on your Chevrolet’s dashboard?

That light is your car signaling a potential problem. When you take your Chevrolet to a mechanic, they use an OBD2 scanner to diagnose the issue.

Mechanics connect an OBD2 reader to the 16-pin OBD2 connector, usually located beneath the steering wheel area. This tool sends ‘OBD2 requests’ to your Chevrolet, and the car responds with ‘OBD2 responses’. These responses can include data like speed, fuel level, and Diagnostic Trouble Codes (DTCs), enabling faster and more accurate troubleshooting.

Alt text: Chevrolet dashboard check engine light illuminated, indicating OBD2 system alert.

Is My Chevrolet OBD2 Compliant?

Almost certainly, yes!

Nearly all modern Chevrolet vehicles, except fully electric models, are equipped with OBD2 and typically operate on the CAN bus system. For older Chevrolet models, even if a 16-pin OBD2 connector is present, it might not fully support the OBD2 protocol. To confirm OBD2 compliance, consider the vehicle’s year of manufacture and where it was originally sold:

Alt text: Chart showing OBD2 compliance by region and vehicle type, helpful for Chevrolet owners.

A Brief History of OBD2 and Chevrolet

The OBD2 system has its roots in California, where the California Air Resources Board (CARB) mandated OBD for all new vehicles starting in 1991 to monitor and control emissions. This standard quickly became crucial for automotive diagnostics and repair.

The Society of Automotive Engineers (SAE) played a key role by recommending the OBD2 standard, leading to standardized DTCs and OBD connectors across all vehicle manufacturers, including Chevrolet. This standardization was formalized in SAE J1962, ensuring consistency in diagnostic interfaces.

The adoption of OBD2 was phased in globally:

1996: OBD2 became mandatory in the USA for all cars and light trucks, including Chevrolet models sold in the US market.
2001: OBD2 adoption became mandatory in the EU for gasoline cars, impacting Chevrolet vehicles sold in European markets.
2003: The EU mandate expanded to include diesel cars (EOBD), further standardizing diagnostics for Chevrolet diesel models in Europe.
2005: OBD2 was required in the US for medium-duty vehicles, extending its application to Chevrolet’s commercial vehicle range.
2008: US vehicles were required to use ISO 15765-4 (CAN) as the communication foundation for OBD2, influencing Chevrolet’s communication protocols.
2010: OBD2 became mandatory for heavy-duty vehicles in the US, completing the rollout across all vehicle classes, including Chevrolet’s heavy-duty lineup.

Alt text: Timeline infographic of OBD2 history and emission control standards relevant to Chevrolet vehicles.

Alt text: Visual timeline summarizing the history of OBD2 adoption and its impact on automotive diagnostics.

Alt text: Graphic depicting the future trends of OBD3 and remote diagnostics in the automotive industry.

The Future of OBD2 in Chevrolet and Beyond

OBD2 remains a vital technology, but its role is evolving.

Here are key trends shaping the future of OBD2:

Originally designed for emissions control, legislative OBD2 requirements don’t explicitly extend to electric vehicles. Consequently, most modern electric vehicles, including some Chevrolet EVs, do not support standard OBD2 requests. Instead, they often use OEM-specific UDS communication protocols. This shift can make accessing data from EVs challenging unless decoding methods are reverse-engineered. However, for Chevrolet’s traditional combustion engine vehicles, OBD2 remains the standard.

Modern alternatives like WWH-OBD (World Wide Harmonized OBD) and OBDonUDS (OBD on UDS) are emerging to address limitations in data richness and lower-layer protocols of OBD2. These protocols aim to enhance OBD communication by using the UDS protocol as a foundation. For deeper insights into these protocols, refer to our introduction to UDS.

In an increasingly connected world, traditional OBD2 testing methods can seem outdated. Manual emission checks are time-consuming and costly.

The proposed solution is OBD3 – integrating telematics into all vehicles.

OBD3 envisions adding a small radio transponder to all cars, including Chevrolets, enabling wireless transmission of the Vehicle Identification Number (VIN) and DTCs to a central server for automated checks.

Many current devices, such as the CANedge2 WiFi CAN logger and CANedge3 3G/4G CAN logger, already facilitate data transfer via WiFi/cellular networks.

While this offers cost and convenience benefits, it also raises political and privacy concerns related to surveillance.

The original purpose of OBD2 was for in-shop emission controls.

However, third parties now extensively use OBD2 to generate real-time data through OBD2 dongles, CAN loggers, and similar devices. The German car industry is seeking to change this trend, as highlighted in this article:

OBD was designed for vehicle servicing in repair shops, not for creating a data-driven economy accessible to third parties through this interface.”

– Christoph Grote, SVP Electronics, BMW (2017)

The industry proposal involves potentially disabling OBD2 functionality during normal driving, centralizing data collection within manufacturer servers. This would give manufacturers control over automotive big data.

Arguments for this change often cite security concerns, such as reducing car hacking risks. However, many view it as a commercially motivated move. The future of this proposal and its potential to disrupt the OBD2 third-party services market remains uncertain.

Alt text: Illustration of an OBD2 connector removed from an electric vehicle, symbolizing data access limitations.

Enhance Your CAN Bus Knowledge

Want to become a CAN bus expert and better understand your Chevrolet’s systems?

Download our comprehensive 160+ page PDF guide, featuring 12 simple introductions:

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OBD2 Standards for Chevrolet Vehicles

On-board diagnostics, or OBD2, is a higher-layer protocol, acting as a language for vehicle communication. CAN bus is the communication method itself, akin to a phone line. OBD2 is similar to other CAN-based higher-layer protocols like J1939, CANopen, and NMEA 2000.

OBD2 standards define the OBD2 connector, lower-layer protocols, OBD2 parameter IDs (PIDs), and more, ensuring consistent diagnostics across Chevrolet models and other brands.

These standards can be structured using a 7-layer OSI model. The following sections focus on the most critical aspects for Chevrolet owners and technicians.

You’ll notice that both SAE and ISO standards cover multiple layers. This reflects the standards established for OBD in the USA (SAE) and Europe (ISO). Many of these standards are technically very similar, such as SAE J1979 and ISO 15031-5, and SAE J1962 and ISO 15031-3.

Alt text: OSI model diagram comparing OBD2 and CAN bus layers, relevant for understanding Chevrolet diagnostic systems.

Alt text: OBD2 connector pinout diagram, Type A female socket, essential for Chevrolet diagnostics.

The OBD2 Connector: SAE J1962 Standard

The 16-pin OBD2 connector, specified in SAE J1962 / ISO 15031-3, allows easy access to data from your Chevrolet.

The illustration shows a Type A OBD2 pin connector (also known as the Data Link Connector, or DLC).

Key points to note:

The connector is typically located near the steering wheel in your Chevrolet, but it may be somewhat hidden.
Pin 16 provides battery power, often even when the ignition is off, which is important for certain diagnostic procedures.
The OBD2 pinout configuration depends on the communication protocol used by your Chevrolet model.
CAN bus is the most common lower-layer protocol. Pins 6 (CAN-H) and 14 (CAN-L) are usually connected in CAN-based Chevrolet systems.

OBD2 Connector Types: A vs. B

You might encounter both Type A and Type B OBD2 connectors. Type A is standard in cars and light trucks, including most Chevrolet passenger vehicles, while Type B is more common in medium and heavy-duty vehicles.

Both types have similar OBD2 pinouts, but they differ in power supply outputs: Type A typically provides 12V, and Type B provides 24V. Baud rates can also vary; cars often use 500K, while heavy-duty vehicles commonly use 250K (with increasing support for 500K).

Type B OBD2 connectors have a distinguishing interrupted groove in the middle. A Type B OBD2 adapter cable is compatible with both Type A and B sockets, but a Type A adapter will not fit into a Type B socket. This is important for selecting the correct diagnostic tools for different Chevrolet vehicles.

Alt text: Diagram comparing OBD2 Connector Type A and Type B, highlighting differences for Chevrolet vehicle applications.

Alt text: Graphic comparing OBD2 and CAN bus protocols according to ISO 15765 standards.

OBD2 and CAN Bus: ISO 15765-4 in Chevrolet

Since 2008, CAN bus has been the mandatory lower-layer protocol for OBD2 in all vehicles sold in the US, as per ISO 15765. This standard is crucial for modern Chevrolet diagnostics.

ISO 15765-4 (also known as Diagnostics over CAN or DoCAN) specifies restrictions applied to the CAN standard (ISO 11898).

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, common in various Chevrolet models.
CAN IDs can be 11-bit or 29-bit, depending on the specific Chevrolet ECU and system.
Specific CAN IDs are designated for OBD requests and responses, ensuring standardized communication.
Diagnostic CAN frame data length is fixed at 8 bytes for OBD2 compliance.
The OBD2 adapter cable should not exceed 5 meters in length to maintain signal integrity.

OBD2 CAN Identifiers (11-bit, 29-bit) in Chevrolet Systems

OBD2 communication always involves request/response message pairs.

In most Chevrolet cars, 11-bit CAN IDs are used for OBD2 communication. The ‘Functional Addressing’ ID is 0x7DF, which broadcasts a request to all OBD2-compatible ECUs, asking if they have data for the requested parameter (as defined in ISO 15765-4). CAN IDs ranging from 0x7E0 to 0x7E7 can be used for ‘Physical Addressing’ requests to specific ECUs, though this is less common in typical OBD2 diagnostics.

ECUs respond with 11-bit IDs from 0x7E8 to 0x7EF. The most common response ID is 0x7E8 (ECM, Engine Control Module), and sometimes 0x7E9 (TCM, Transmission Control Module).

In some Chevrolet vehicles, especially vans and light/medium/heavy-duty models, extended 29-bit CAN identifiers might be used for OBD2 communication instead of 11-bit IDs.

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

Responses will use CAN IDs from 0x18DAF100 to 0x18DAF1FF (typically 18DAF110 and 18DAF11E). The response ID is also sometimes represented in ‘J1939 PGN’ format, specifically PGN 0xDA00 (55808), which is reserved for ISO 15765-2 in the J1939-71 standard.

Alt text: Diagram illustrating OBD2 protocol request and response frames with PID data parameters.

Alt text: Comparison of OBD2 standard CAN bus and proprietary OEM-specific CAN bus data in vehicles.

OBD2 vs. Chevrolet Proprietary CAN Protocols

It’s crucial to understand that your Chevrolet’s electronic control units (ECUs) operate using proprietary CAN protocols designed by Chevrolet, not OBD2. OBD2 is an additional protocol layered on top for diagnostic purposes. These proprietary CAN protocols are specific to Chevrolet’s vehicle brand, model, and year. Interpreting this data without OEM tools or reverse engineering is generally not possible.

When you connect a CAN bus data logger to your Chevrolet’s OBD2 connector, you might observe the OEM-specific CAN data, often broadcast at 1000-2000 frames/second. However, many newer Chevrolet models employ a ‘gateway’ that restricts access to this CAN data, allowing only OBD2 communication through the OBD2 connector.

In essence, OBD2 in your Chevrolet is an ‘extra’ higher-layer protocol functioning in parallel with Chevrolet’s OEM-specific protocol.

Bit-rate and ID Validation for Chevrolet OBD2

OBD2 can use two bit-rates (250K, 500K) and two CAN ID lengths (11-bit, 29-bit), resulting in 4 possible combinations. Modern Chevrolet cars commonly use 500K and 11-bit IDs. External diagnostic tools should systematically verify these settings.

ISO 15765-4 provides a recommended initialization sequence to determine the correct combination. This process relies on the fact that OBD2-compliant vehicles, including Chevrolets, must respond to a specific mandatory OBD2 request (see the OBD2 PID section for details). Incorrect bit-rate transmission will result in CAN error frames, helping to identify the correct setting.

Newer ISO 15765-4 versions account for vehicles that may support OBD communication via OBDonUDS rather than 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 protocol in your Chevrolet, a diagnostic tool can send UDS requests with 11-bit/29-bit functional address IDs for service 0x22 and data identifier (DID) 0xF810 (protocol identification). Vehicles supporting OBDonUDS should have ECUs that respond to this DID.

OBDonEDS (also known as OBD2, SAE OBD, EOBD, or ISO OBD) is prevalent in most non-EV cars today, including Chevrolet’s combustion engine models, while WWH-OBD is mainly used in EU trucks and buses.

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

Alt text: Graphic showing the five lower-layer OBD2 protocols including CAN, KWP2000, SAE J1850, and ISO9141.

Five Lower-Layer OBD2 Protocols for Older Chevrolets

While CAN bus is the dominant lower-layer protocol for OBD2 in most modern vehicles, including recent Chevrolet models, older Chevrolets (pre-2008) might use one of four other lower-layer protocols. Understanding these can be helpful when diagnosing older vehicles. The pinouts on the OBD2 connector can sometimes indicate which protocol is in use.

ISO 15765 (CAN bus): Mandatory in US cars since 2008 and now widely used in most vehicles, including Chevrolet.
ISO14230-4 (KWP2000): Keyword Protocol 2000 was common in 2003+ vehicles, including some Chevrolet models, particularly in Asian markets.
ISO 9141-2: Used in EU, Chrysler, and Asian cars in 2000-04, potentially found in some early 2000s Chevrolet models.
SAE J1850 (VPW): Primarily used in older GM vehicles, including some older Chevrolet models.
SAE J1850 (PWM): Mostly used in older Ford vehicles, less relevant for Chevrolet diagnostics.

Transporting OBD2 Messages via ISO-TP: ISO 15765-2 in Chevrolet

All OBD2 data communication in Chevrolet vehicles, like others, utilizes the ISO-TP (ISO 15765-2) transport protocol over CAN bus. This protocol allows for transmitting data payloads larger than 8 bytes, necessary for OBD2 functions like retrieving the Vehicle Identification Number (VIN) or Diagnostic Trouble Codes (DTCs). ISO 15765-2 manages segmentation, flow control, and reassembly of these larger messages. For more details, refer to our introduction to UDS.

However, much of the OBD2 data fits within a single CAN frame. In these cases, ISO 15765-2 specifies using a ‘Single Frame’ (SF), where the first data byte (PCI field) indicates the payload length (excluding padding), leaving 7 bytes for OBD2 communication.

Alt text: Diagram illustrating ISO 15765-2 ISO-TP OBD2 frame types and structure.

Decoding the OBD2 Diagnostic Message: SAE J1979, ISO 15031-5 for Chevrolet

To better understand OBD2 communication on CAN in your Chevrolet, let’s examine a raw ‘Single Frame’ OBD2 CAN message. An OBD2 message consists of an identifier, data length (PCI field), and data. The data section is further broken down into Mode, parameter ID (PID), and data bytes.

Alt text: Breakdown of OBD2 message structure, showing Mode, PID, and data bytes, essential for Chevrolet diagnostics.

Example: OBD2 Request/Response in a Chevrolet

Consider this example of a request/response for ‘Vehicle Speed’.

An external tool sends a request to the Chevrolet with CAN ID 0x7DF, containing 2 payload bytes: Mode 0x01 and PID 0x0D. The Chevrolet responds with CAN ID 0x7E8 and 3 payload bytes, including the vehicle speed value in the 4th byte, 0x32 (50 in decimal).

By consulting the decoding rules for OBD2 PID 0x0D, we find that the physical value is 50 km/h.

Next, we’ll explore OBD2 modes and PIDs in more detail.

Alt text: Example of OBD2 request (7DF) and response (7E8) CAN frames for vehicle speed data.

Alt text: Example of OBD2 PID 0D for vehicle speed, showing data byte and physical value conversion.

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

The 10 OBD2 Services (Modes)

There are 10 defined OBD2 diagnostic services, also known as modes. Mode 0x01 provides current real-time data, while others are used to display or clear diagnostic trouble codes (DTCs) or show freeze frame data.

Chevrolet vehicles may not support all 10 OBD2 modes and might also include OEM-specific modes beyond these standard ones.

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

OBD2 Parameter IDs (PIDs) for Chevrolet Diagnostics

Each OBD2 mode contains parameter IDs (PIDs).

For instance, mode 0x01 includes approximately 200 standardized PIDs providing real-time data on parameters like speed, RPM, and fuel level. However, a Chevrolet vehicle may not support all PIDs within a mode. In practice, most vehicles support only a subset of these PIDs.

One PID is particularly significant:

If an emissions-related ECU supports any OBD2 services, it must support mode 0x01 PID 0x00. Responding to this PID, the vehicle ECU indicates whether it supports PIDs 0x01-0x20. This makes PID 0x00 a fundamental ‘OBD2 compatibility test’. Similarly, PIDs 0x20, 0x40, …, 0xC0 can be used to determine support for the remaining mode 0x01 PIDs.

Alt text: Diagram of OBD2 request and response frames with parameter ID (PID) and data parameters.

Alt text: Screenshot of an OBD2 PID overview tool interface, useful for Chevrolet diagnostics.

Tip: OBD2 PID Overview Tool

The appendices of SAE J1979 and ISO 15031-5 detail the scaling information for standard OBD2 PIDs, enabling you to convert raw data into physical values (as explained in our CAN bus introduction).

For quick lookup of mode 0x01 PIDs, use our OBD2 PID overview tool. It assists in constructing OBD2 request frames and dynamically decoding OBD2 responses, streamlining Chevrolet diagnostics.

OBD2 PID overview tool

Logging and Decoding OBD2 Data from Your Chevrolet

This section provides a practical guide on logging OBD2 data using the CANedge CAN bus data logger in your Chevrolet.

The CANedge allows you to configure custom CAN frames for transmission, making it suitable for OBD2 logging.

Once configured, you can easily connect the CANedge to your Chevrolet using our OBD2-DB9 adapter cable.

Alt text: Diagram showing OBD2 PID data logging with request (7DF) and response (7E8) frames using a data logger.

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: Screenshot of OBD2 PID lookup tool displaying supported PIDs for a vehicle.

Step #1: Bit-rate, ID, and Supported PID Testing

As discussed, ISO 15765-4 outlines how to determine the correct bit-rate and IDs for a specific vehicle. Use the CANedge to perform these tests as follows (see the CANedge Intro for detailed instructions):

Send a CAN frame at 500K and verify successful transmission (if unsuccessful, try 250K).
Use the verified bit-rate for subsequent communication.
Send multiple ‘Supported PIDs’ requests and examine the responses.
Determine 11-bit vs. 29-bit IDs based on response IDs.
Identify supported PIDs based on response data.

We provide ready-to-use configurations to facilitate these tests.

Most Chevrolet vehicles manufactured in 2008 or later (non-EV models) support 40-80 PIDs using a 500K bit-rate, 11-bit CAN IDs, and the OBD2/OBDonEDS protocol.

As shown in the asammdf GUI screenshot, you might receive multiple responses to a single OBD request. This is because using the 0x7DF request ID polls all ECUs for responses. Since all OBD2/OBDonEDS-compliant ECUs must support service 0x01 PID 0x00, numerous responses to this PID are common. As evident, fewer ECUs respond to subsequent ‘Supported PIDs’ requests. Note that the ECM ECU (0x7E8) supports all PIDs supported by other ECUs in this example. Busload can be reduced by directing subsequent requests specifically to this ECU using the ‘Physical Addressing’ CAN ID 0x7E0.

Step #2: Configuring OBD2 PID Requests

Once you know the supported OBD2 PIDs for your Chevrolet, along with the correct bit-rate and CAN IDs, you can configure your transmit list with the PIDs you want to monitor.

Consider these points:

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 overwhelming ECUs.
Battery Drain: Use triggers to stop transmissions when the vehicle is inactive to avoid battery drain from waking up ECUs.
Filters: Implement filters to record only OBD2 responses, especially if your Chevrolet also outputs OEM-specific CAN data.

With these configurations, your device is ready to log raw OBD2 data from your Chevrolet!

An example list of CANedge OBD2 PID requests for data logging.

asammdf software visualizes decoded OBD2 data from a CAN bus DBC file.

Step #3: DBC Decoding of Raw OBD2 Data

To analyze and visualize your logged data, you need to decode the raw OBD2 data into physical values (like km/h or °C).

Decoding information is available in ISO 15031-5/SAE J1979 and online resources like Wikipedia. For convenience, we offer a free OBD2 DBC file that simplifies DBC decoding of raw OBD2 data in most CAN bus software tools.

Decoding OBD2 data is slightly more complex than standard CAN signals because different OBD2 PIDs are transmitted using the same CAN ID (e.g., 0x7E8). The CAN ID alone is not enough to identify the encoded signals in the payload.

To address this, you must use the CAN ID, OBD2 mode, and OBD2 PID to identify the signal. This form of multiplexing, known as ‘extended multiplexing,’ can be implemented in DBC files.

CANedge: Your OBD2 Data Logger for Chevrolet Vehicles

The CANedge provides an easy way to record OBD2 data onto an 8-32 GB SD card. Simply connect it to your Chevrolet to start logging and decode the data using free software/APIs and our OBD2 DBC.

OBD2 logger intro
CANedge product page

OBD2 Multi-Frame Examples: ISO-TP in Action

OBD2 data communication, including in Chevrolet vehicles, relies on the ISO-TP (transport protocol) as per ISO 15765-2. While many examples are single-frame communications, multi-frame communication is essential for larger data sets.

Multi-frame OBD2 communication requires flow control frames (see our UDS intro). In practice, you can transmit a static flow control frame approximately 50 ms after the initial request frame, as demonstrated in the CANedge configuration example.

Analyzing multi-frame OBD2 responses requires CAN software/API tools that support ISO-TP, such as the CANedge MF4 decoders.

Alt text: Example of an OBD2 multi-frame request message for Vehicle Identification Number (VIN).

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

The Vehicle Identification Number (VIN) is crucial for telematics, diagnostics, and more. To retrieve the VIN from your Chevrolet using OBD2, use mode 0x09 and PID 0x02:

The diagnostic tool sends a Single Frame request with 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 byte 0x01, indicating the Number Of Data Items (NODI), which is 1 in this case (see ISO 15031-5 / SAE J1979 for details). The subsequent 17 bytes represent the VIN, which can be converted from HEX to ASCII as discussed in our UDS introduction.

Example 2: Chevrolet Multi-PID Request (6x)

External tools can request up to 6 mode 0x01 OBD2 PIDs in a single request frame. The ECU will respond with data for supported PIDs (omitting unsupported ones), potentially using multiple frames as per ISO-TP.

This efficient method allows for higher frequency data collection, but the signal encoding is specific to your request method. This can complicate using generic OBD2 DBC files. We generally do not recommend this method for practical use. Below is an example trace:

The multi-frame response is similar to the VIN example, but the payload includes the requested PIDs and their corresponding data. The PIDs in the example are ordered as requested, which is common but not strictly mandated by ISO 15031-5.

Decoding such responses using generic DBC files is challenging. We advise against this approach for practical data logging unless you are using a tool specifically designed for multi-PID requests. It introduces extended multiplexing complexities, making it difficult to generalize DBC files across different vehicles or even across different requests to the same vehicle if supported PIDs vary. Managing this at scale, especially with multiple multi-PID requests, becomes impractical without custom scripting to interpret responses in conjunction with requests.

Example 3: Chevrolet Diagnostic Trouble Codes (DTCs) via OBD2

You can use OBD2 mode 0x03, ‘Show stored Diagnostic Trouble Codes,’ to request emissions-related DTCs. No PID is included in the request. The targeted ECU(s) will respond with the number of stored DTCs (possibly zero if none are present), with each DTC occupying 2 data bytes. Multi-frame responses are necessary when more than two DTCs are stored.

The 2-byte DTC value is structured as per ISO 15031-5/ISO 15031-6. The first 2 bits define the ‘category,’ and the remaining 14 bits define a 4-digit hexadecimal code, as shown visually. 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.

Alt text: Diagram explaining OBD2 DTC (Diagnostic Trouble Code) DBC interpretation and decoding.

Real-World Applications of Chevrolet OBD2 Data Logging

OBD2 data from Chevrolet cars and light trucks can be applied in various scenarios:

Car Data Logging for Chevrolet Fleets and Personal Use

OBD2 data logging in Chevrolet vehicles can optimize fuel consumption, improve driving habits, test prototype components, and refine insurance models.

OBD2 logger product link

Real-Time Chevrolet Vehicle Diagnostics

OBD2 interfaces allow streaming human-readable OBD2 data in real-time, which is invaluable for diagnosing vehicle issues in Chevrolet service centers and by enthusiasts.

OBD2 streaming solution

Predictive Maintenance for Chevrolet Vehicles

Monitoring Chevrolet cars and light trucks via IoT-connected OBD2 loggers enables predictive maintenance, helping to anticipate and prevent breakdowns, reducing downtime and repair costs for fleet operators and individual owners.

Predictive maintenance solutions

Chevrolet Vehicle Black Box Recording

An OBD2 logger can serve as a ‘black box’ in Chevrolet vehicles, providing crucial data for incident analysis, warranty claims, and diagnostic accuracy in case of disputes or failures.

CAN bus black box logger

Do you have a specific OBD2 data logging application in mind for your Chevrolet? Contact us for expert consultation!

Explore our guides section for more introductions, or download the ‘Ultimate Guide’ PDF for comprehensive CAN bus knowledge.

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