Decoding Your 2013 Honda Fit OBD2 Port with OBDLink SX

For automotive enthusiasts and DIY mechanics, understanding your vehicle’s onboard diagnostics system is crucial. If you own a 2013 Honda Fit, accessing data through its OBD2 port opens up a world of diagnostic possibilities. This guide will walk you through using the OBDLink SX scan tool to communicate with your Honda Fit, retrieve valuable data, and even delve into the CAN bus network.

Understanding OBDLink SX and Your 2013 Honda Fit’s OBD2 System

The OBDLink SX is a popular and capable OBD-II adapter known for its speed and reliability. It allows you to interface with your car’s computer system, reading diagnostic trouble codes, accessing live data parameters, and performing various diagnostic tests. The 2013 Honda Fit, like all modern vehicles, is equipped with an OBD2 port, standardized under SAE J1962. This port provides access to essential vehicle information mandated for emissions testing and broader diagnostics.

This article provides notes and commands specifically for using the OBDLink SX with a 2013 Honda Fit Obd2 system. We’ll cover basic setup, useful AT commands for device control, and advanced ST commands for deeper diagnostics, including CAN bus monitoring.

OBDLink SX r4.2 Hardware ID String

Essential AT Commands for OBDLink SX

AT commands are the foundation for communicating with your OBDLink SX device. They are simple text-based commands sent to the adapter to control its behavior and retrieve information. Here are some of the most useful AT commands:

Display Commands

These commands control how the OBDLink SX displays output in your terminal or diagnostic software:

AT L1 – Turns linefeeds on. This adds a newline character after each response, making the output easier to read in a terminal.
AT L0 – Turns linefeeds off. Removes newline characters from responses, which can be useful for scripting or specific software interfaces.
AT S1 – Turns spaces on. Adds spaces in the output for better readability.
AT S0 – Turns spaces off. Removes extra spaces from the output.
AT E1 – Turns echo on. The OBDLink SX will echo back the commands you send, useful for verifying what you typed.

Device Commands

These commands control the OBDLink SX device itself:

AT I – Displays version information. This command is essential for verifying your device firmware and hardware versions. It will output strings like firmware ID, hardware ID, manufacturer, and serial number, as seen in the original article’s example.
AT Z – Resets the device. This command restarts the OBDLink SX, useful for troubleshooting or starting fresh.

Info Commands

AT RV – Reads voltage on the car end. This command measures the voltage at the OBD2 port connector, giving you an indication of the car’s battery voltage as seen by the adapter.

Advanced ST Commands and Baud Rate Configuration

ST commands are extended commands specific to STN chips used in OBDLink devices, offering more advanced functionalities. However, exercise caution when using these, especially baud rate commands, as incorrect settings can cause communication issues.

Baud Rate Commands

Baud rate is the speed of serial communication. The OBDLink SX defaults to 115200 baud.

ST BRT [milliseconds] – Sets the baud rate change timeout. This command configures how long the OBDLink SX will wait for a reconnection after a baud rate change. For example, ST BRT 5000 sets a 5-second timeout.
ST SBR [baud rate] – Temporarily changes the UART baud rate. This command allows you to switch to a different baud rate for communication. For instance, ST SBR 500000 attempts to switch to 500000 baud. Be very careful when changing baud rates, and ensure your terminal or software is configured to match. Incorrect baud rate settings can make the device unresponsive until reset.

Caution: Changing baud rates, especially permanently, can lead to communication problems if not handled correctly. Double-check your settings and procedures before altering baud rates.

Dumping CAN Bus Data on Your 2013 Honda Fit

For advanced diagnostics and reverse engineering, accessing the CAN bus network is invaluable. The following commands are designed to set up your OBDLink SX to monitor and log CAN bus traffic on your 2013 Honda Fit.

Setting Up for CAN Monitoring

These AT commands configure the OBDLink SX for CAN bus monitoring:

AT AT2 – Turns on adaptive timing mode 2. This optimizes timing for faster and more reliable communication.
AT H1 – Turns on headers. This includes header information in the output data, providing more detail about the messages.
AT AL – Allows messages longer than 7 bytes. CAN bus messages can be up to 8 bytes of data, and this command ensures that longer messages are not truncated.
AT SP 7 – Sets the protocol to ISO 15765-4 (CAN 29/500). This is the standard CAN protocol used in many vehicles, including the 2013 Honda Fit, for high-speed communication.
AT DP – Describes the current protocol. Verifies that the protocol has been set correctly.

CAN Bus Monitoring Commands

These ST commands initiate CAN bus monitoring:

STP 34 – Sets the CAN protocol to ISO 15765-4 (CAN 29/500). This command, similar to AT SP 7, specifically configures the STN chip for the CAN protocol.
ST CMM1 – Selects CAN monitor mode. This undocumented command is crucial for enabling the OBDLink SX to passively listen to all CAN bus traffic without sending requests.
ST MA – Starts monitoring the CAN network. This command initiates the data stream. The OBDLink SX will begin outputting CAN bus messages until its buffer is full.

Human-Readable CAN Dump Setup

For a complete, human-readable CAN bus dump, you can combine the commands for easier interpretation in a terminal:

Establish Serial Connection: Connect to your OBDLink SX using a serial terminal program like screen or minicom at 115200 baud. Common port names are /dev/ttyUSB0 (Linux) or /dev/tty.usbserial-xxxx (macOS).
```
screen /dev/ttyUSB0 115200
```
Human-Readable Output: Configure the output for easy reading:
```
>AT L1 (Linefeeds on)
>AT S1 (Spaces on)
>AT E1 (Echo on)
```
Baud Rate Adjustment (Optional and Use with Caution): If needed and you know what you are doing, you can adjust the baud rate.
```
>ST BRT 5000 (Set baud switch timeout to 5 seconds)
>ST SBR 500000 (Set new baud rate to 500000)
```
If you changed the baud rate, reconnect your serial terminal at the new baud rate within 5 seconds (as set by ST BRT).
```
screen /dev/ttyUSB0 500000
```
Test the new baud rate with AT I. If you want to make the baud rate change permanent, use ST WBR (Use with extreme caution!)

Configure Data Display & Protocol: Set up headers, protocol, and timing:

>AT AT2 (Adaptive timing mode 2)
>AT H1 (Headers on)
>AT AL (Allow long messages)
>AT SP 7 (Set protocol ISO 15765-4)
>AT DP (Describe protocol)

Basic Data Request (Test): Send a basic PID request to ensure communication:

>0100 (Request PIDs supported 01-20)
>0300 (Request trouble codes - for testing)

Start CAN Bus Monitoring: Initiate CAN bus data logging:
```
>STP 34 (Set CAN protocol ISO 15765-4)
>ST CMM1 (CAN monitor mode ON)
>ST MA (Start monitoring CAN bus)
```
The OBDLink SX should now start streaming CAN bus data to your terminal. Press Enter to keep the data flowing if needed, as mentioned in the original notes.

Conclusion

These notes provide a starting point for using your OBDLink SX with a 2013 Honda Fit OBD2 system. By understanding AT and ST commands, you can effectively diagnose issues, retrieve vehicle data, and even monitor the CAN bus network. Remember to exercise caution with advanced commands, especially those related to baud rate and CAN bus configuration. Always refer to the OBDLink SX documentation and relevant vehicle service manuals for comprehensive information. Exploring your 2013 Honda Fit OBD2 port opens up exciting possibilities for vehicle diagnostics and understanding your car’s inner workings.