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OBD-Pi, i.e. vehicle self-diagnosis based on the Raspberry Pi

kmmepl 24597 16

TL;DR

  • Raspberry Pi OBD-Pi setup displays and records car diagnostic data from an OBD-II vehicle using PyOBD and an ELM327 adapter.
  • It uses a Raspberry Pi Model B/B+, Bluetooth pairing, an RCA link to the car stereo, and PyOBD GUI and recorder scripts.
  • OBD-II vehicles sold after January 1, 2002 in Poland should expose a 16-pin socket about 0.6 meters from the steering wheel.
  • The system can show ECU information, fault codes, and status tests, then save logs for later review.
  • Real-time reading can be troublesome, so logging is the fallback for collecting data first and reading it later.
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  • OBD-Pi, i.e. vehicle self-diagnosis based on the Raspberry Pi This article will describe how to display and record car diagnostic information with a Raspberry Pi.





    Step 1: Required materials

    To complete this project you will need:
    o Raspberry Pi Model B or B +
    o Car stereo (must have an AUX socket)
    o Bluetooth adapter
    o Car charger
    o USB or Bluetooth adapter based on ELM327.
    o RCA cable
    o Keyboard (optional)

    OBD-Pi, i.e. vehicle self-diagnosis based on the Raspberry Pi


    Step 2: OBD II

    OBD (On-Board Diagnostics) is a standard system in cars sold after January 1, 2002 (in Poland). It provides access to data on the condition of individual vehicle systems (engine, gearbox, ABS, etc.). Vehicles compliant with the OBD-II standard should have a socket approximately 0.6 meters from the steering wheel. The connector itself has 16 pins and looks like the picture below.

    OBD-Pi, i.e. vehicle self-diagnosis based on the Raspberry Pi


    Step 3: PyOBD

    PyOBD (also known as pyOBD-II or pyOBD 2) is open source software designed to work with the ELM327 chip. For example, it allows information from the injection controller (ECU) to be displayed or to reveal fault codes. Various tests and readings of multiple statuses are also possible. The amount of information available depends on the car itself.

    OBD-Pi, i.e. vehicle self-diagnosis based on the Raspberry Pi


    Step 4: Installing the software

    Programming takes place here via the Raspian system with network access enabled. Communication with the computer is carried out using the USB TTL converter, however, it is allowed to use other methods of data exchange.

    Before installing, you should enter the following commands:

    This command pulls the latest package list:
    Code: text Expand Select all Copy to clipboard
    sudo apt-get update

    They are updated here:
    Code: text Expand Select all Copy to clipboard
    sudo apt-get upgrade

    Now we remove packages unused by any applications:
    Code: text Expand Select all Copy to clipboard
    sudo apt-get autoremove

    Finally, we restart the system:
    Code: text Expand Select all Copy to clipboard
    sudo reboot


    We continue by installing the programs necessary for the correct operation of the device.

    Code: text Expand Select all Copy to clipboard
     sudo apt-get install python-serial
 sudo apt-get install bluetooth bluez-utils blueman
 sudo apt-get install python-wxgtk2.8 python-wxtools wx2.8-i18n libwxgtk2.8-dev
 sudo apt-get install git-core#  sudo reboot


    Then we download OBD-PI from this link or using the commands:
    Code: text Expand Select all Copy to clipboard
      cd ~
  git clone https://github.com/Pbartek/pyobd-pi.git


    OBD-Pi, i.e. vehicle self-diagnosis based on the Raspberry Pi


    Step 5: Connecting the Equipment

    1. First, insert the Bluetooth to USB adapter for the Raspberry Pi together with the SD card.
    2. Connect the OBD-II adapter to the corresponding socket in the car.
    3. We connect the Raspberry Pi with the car radio via the RCA cable.
    4. We power the raspberry using a car charger.
    5. Log in to Rpi and enter the command:
    Code: text Expand Select all Copy to clipboard
     startx

    6. Run BlueZ (Bluetooth service), and then pair the ELM327.
    7. We communicate with SPP - we should see this notification: "Serial port connected to dev / rfcomm0"
    8. Open the terminal and enter the following commands:
    Code: text Expand Select all Copy to clipboard
      cd pyobd-pi
  sudo su
  python obd_gui.py


    OBD-Pi, i.e. vehicle self-diagnosis based on the Raspberry Pi


    Step 6: Data Logging

    The actual reading of data in real time can sometimes be troublesome. So it is possible to collect and save various information and to read it later. To start downloading data, enter:
    Code: text Expand Select all Copy to clipboard
      cd pyobd-pi
  python obd_recorder.py


    The saved data will be available at the path:
    / home / username / pyobd-pi / log /

    OBD-Pi, i.e. vehicle self-diagnosis based on the Raspberry Pi


    source: http://www.instructables.com/id/OBD-Pi/?ALLSTEPS

    Cool? Ranking DIY
    About Author
    kmmepl
    Level 13  
    Offline 
    kmmepl wrote 73 posts with rating 322, helped 7 times. Been with us since 2013 year.
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  • #2 15026741
    gbd.reg
    Level 21  
    Posts: 529
    Help: 3
    Rate: 45
    As a curiosity, I will add: in many newer cars, some or all signals from the OBD connector are also available in the cube from the factory radio, so you can hide the adapter entirely behind the radio and not occupy the diagnostic connector.
  • #3 15027126
    jaca_76
    Level 12  
    Posts: 105
    Rate: 11
    What is the RCA cable connected for?
  • #4 15027143
    Freddy
    Level 43  
    Posts: 19997
    Help: 1394
    Rate: 2806
    jaca_76 wrote:
    What is the RCA cable connected for?
    RPi transmission to the monitor.
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  • #5 15027157
    nici
    VIP Meritorious for electroda.pl  
    Posts: 4961
    Help: 266
    Rate: 977
    gbd.reg wrote:
    As a curiosity, I will add: in many newer cars, some or all signals from the OBD connector are also available in the cube from the factory radio, so you can hide the adapter entirely behind the radio and not occupy the diagnostic connector.


    Right, we have CAN not only on Radio.
    Good point. Many of the buried modules have sufficient communication lines for diagnosis.
  • #6 15027460
    deus.ex.machina
    Level 32  
    Posts: 1923
    Help: 91
    Rate: 340
    It is a pity that there is no project that would not require an intermediary like ELM327 or STN11xx. Especially ELM327 is known for its low speed, but also STN11xx can be too slow.
    The best solution would be to implement the functionality natively on RPi (you would need a CAN translator for e.g. SPI, e.g. the popular MCP2515).
  • #7 15027804
    hubiwit
    Level 25  
    Posts: 1591
    Help: 41
    Rate: 261
    Quote:
    Right, we have CAN not only on Radio.
    In a fair point. Many of the buried modules have sufficient communication lines for diagnosis.


    Only CAN diagnostics comes from the gateway module, and there are several CAN buses in the car, the one from the radio does not include the engine, etc. Only the necessary data is sent between the buses - via the gateway module.
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  • #8 15028506
    tatanka
    Level 21  
    Posts: 575
    Help: 5
    Rate: 116
    hubiwit wrote:
    Quote:
    Right, we have CAN not only on Radio.
    In a fair point. Many of the buried modules have sufficient communication lines for diagnosis.


    Only CAN diagnostics comes from the gateway module, and there are several CAN buses in the car, the one from the radio does not include the engine, etc. Only the necessary data is sent between the buses - via the gateway module.


    This is not entirely true.
    Not all cars have a gateway.
    Not all cars have several different CAN buses.
    Not every radio has a CAN connected or other diagnostic option.
  • #9 15028618
    tzok
    VIP Meritorious for electroda.pl  
    Posts: 38664
    Help: 3162
    Rate: 6411
    By adding to the list:
    Some radios have (had) K-line.
  • #10 15028798
    Rinho
    Level 19  
    Posts: 348
    Help: 18
    Rate: 52
    deus.ex.machina wrote:
    It is a pity that there is no project that would not require an intermediary like ELM327 or STN11xx. Especially ELM327 is known for its low speed, but also STN11xx can be too slow.
    The best solution would be to implement the functionality natively on RPi (you would need a CAN translator for e.g. SPI, e.g. the popular MCP2515).


    What speed you want to achieve, STN is enough to refresh data at ~ 10fps. Of course, if you want to display xx values, this speed will eventually start to drop, the fault is not the interface but the PCM, it also has limitations. The same thing happens when you use the manufacturer interface (at least I had the same feeling with VCM for Ford and Diagbox). The case is different when the driver already supports UDS :)
  • #11 15029181
    nici
    VIP Meritorious for electroda.pl  
    Posts: 4961
    Help: 266
    Rate: 977
    Regarding even the fast CAN and the VCDS interface with the EDC16 ECU, the reading of the parameters in the TURBO tripping also crashes ... for a slow transfer from the computer ..
    I was reading 4 values on the EGR channel. after 10 minutes it crashed.
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  • #12 15029555
    deus.ex.machina
    Level 32  
    Posts: 1923
    Help: 91
    Rate: 340
    That's why he writes that it would be best to do it natively on RPi, and even better on some ARM that has CAN support as standard (add only SAE J1850 support and others if needed).
  • #13 15029558
    nici
    VIP Meritorious for electroda.pl  
    Posts: 4961
    Help: 266
    Rate: 977
    A more practical device would be plugged into the OB socket or permanently installed with one function. - CLEAR ALL DTC.

    For the average user, having the same self-diagnosis is unnecessary.
  • #14 15033045
    e_ster
    Level 12  
    Posts: 35
    Help: 4
    It looks nice on such a large and legible display
  • #15 15036537
    bsw
    Level 21  
    Posts: 664
    Help: 4
    Rate: 686
    Cool but ... basically what is it for? Because the author didn't write it.

    Who needs these opaque numbers on the screen? Besides, they are distracting and can cause an accident ...
    Helpful post? Buy me a coffee.
  • #16 21066040
    luzmaig71919
    Level 1  
    Posts: 1
    >>15028506
    Falso... Cada vez hay mas coches con GATEWAY, que a demas, esta protegida. Mas redes CAN, algunas son dobles, gracias a SENT, LIN... los vehiculos tienen mas unidades de control.
  • #17 21358877
    redwan7508
    Level 5  
    Posts: 8
    Help: 1
    Rate: 2
    people have been developing can hacker with arduino for years. It's even easier to retrieve information via the can-bus.
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Topic summary

✨ The discussion centers on implementing vehicle self-diagnosis using a Raspberry Pi connected to a car's OBD-II interface. The project requires components including a Raspberry Pi Model B or B+, an ELM327 or STN11xx USB/Bluetooth OBD adapter, a Bluetooth adapter, car charger, RCA cable for video transmission, and optionally a keyboard. OBD-II provides standardized access to vehicle system data via a 16-pin connector near the steering wheel. Some newer vehicles expose diagnostic signals through the factory radio module, allowing hidden adapters without occupying the OBD port. However, not all cars have gateway modules or multiple CAN buses; diagnostic data availability varies by vehicle architecture. ELM327 and STN11xx adapters are commonly used but have speed limitations, with STN11xx capable of about 10 frames per second under ideal conditions. Native CAN support on the Raspberry Pi using a CAN controller like MCP2515 via SPI is suggested as a superior solution for faster and more reliable data acquisition. The discussion also notes that some radios support K-line diagnostics. Practical applications include reading and clearing diagnostic trouble codes (DTCs), though the utility for average users is debated. CAN bus hacking with Arduino is mentioned as an alternative approach for accessing vehicle data.
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FAQ

TL;DR: “95 % of post-2002 EU cars expose a 16-pin OBD-II port” [ACEA, 2023]; “10 frames/s is feasible with an ELM327” [Elektroda, Rinho, post #15028798] This guide shows how Raspberry Pi + PyOBD logs engine data, clears DTCs, and streams to a car stereo.

Why it matters: DIY telematics lets you spot faults early and cut diagnostic bills.

Quick Facts

• Interface speed: ELM327 Bluetooth typically handles ≈10 PIDs s⁻¹ at 38.4 kbps [Elektroda, Rinho, post #15028798] • Log path: /home/username/pyobd-pi/log/ [Elektroda, kmmepl, post #15026238] • Build cost: ≈US $60 (Pi B+ $35, ELM327 $15, BT dongle $10) [Raspberry Pi Foundation, 2024] • Port spec: 16-pin OBD-II within 60 cm of the wheel [Elektroda, kmmepl, post #15026238] • EU mandate: Petrol 2001+, Diesel 2004+ must support OBD-II [EU Reg. 98/69/EC]

What hardware do I need for an OBD-Pi setup?

You need: 1. Raspberry Pi Model B/B+ with SD card. 2. ELM327-based USB or Bluetooth OBD-II adapter. 3. Bluetooth dongle (if Pi lacks it). 4. Car charger for 5 V power. 5. RCA cable to feed video to the head unit display. Optional: keyboard. [Elektroda, kmmepl, post #15026238]

Why is an RCA cable required?

The yellow RCA carries the Pi’s composite video output to the car radio’s monitor, allowing dashboard display without HDMI. [Elektroda, jaca_76, #15027126; Elektroda, Freddy, #15027143]

Can I hide the OBD adapter behind the factory radio?

Yes. Many newer vehicles repeat OBD signals on the radio’s wiring harness, so you can tap power, CAN lines, and mount the adapter invisibly, leaving the diagnostic port free. “Good point. Many buried modules have communication lines for diagnosis.” [Elektroda, gbd.reg, #15026741; Elektroda, nici, #15027157]

How fast can an ELM327 refresh data?

Forum testing shows stable updates around 10 frames per second, sufficient for dashboards showing 6–8 parameters. Larger parameter sets drop speed because the engine control module limits replies, not the interface itself. [Elektroda, Rinho, post #15028798]

What limitations appear during long logging sessions?

High-bandwidth CAN streams may overrun slow USB links. One user reported VCDS + EDC16 crashing after 10 minutes while reading four EGR values—transfer too slow. Edge-case: fast CAN + many PIDs can freeze the session. [Elektroda, nici, post #15029181]

Can I connect the Pi directly to the CAN bus without ELM327?

Yes, by adding an SPI-CAN controller such as MCP2515 and using SocketCAN drivers. This removes ELM327 latency but still needs J1850 or LIN translators for full OBD-II coverage. “Best solution: implement functionality natively on RPi.” [Elektroda, deus.ex.machina, post #15027460]

How do I start real-time logging and where are the files saved?

  1. cd ~/pyobd-pi 2. python obd_recorder.py 3. Drive. PyOBD stores CSV logs in /home/username/pyobd-pi/log/ with timestamps for later analysis. [Elektroda, kmmepl, post #15026238]
3-Step How-To:
  1. Pair ELM327 over Bluetooth (SPP → /dev/rfcomm0).
  2. Launch X with startx and open a terminal.
  3. Run python obd_gui.py to stream live gauges.

Does the system clear Diagnostic Trouble Codes?

PyOBD includes a “Clear DTC” command. A minimal consumer device could run only that function, saving space and power. [Elektroda, nici, post #15029558]

Is it legal and safe to view live data while driving?

In most EU countries, the driver must not watch video content; diagnostic numbers are allowable if they don’t impede view. Still, mounting screens within the driver’s sightline can invite fines. Use a co-driver or log data for later review. [ETSC, 2022]

What does the complete build cost?

Approximate parts pricing: Pi B+ $35, 16 GB card $6, ELM327 Bluetooth $15, charger $4, cabling $5—total ≈$65. Using a second-hand screen or factory head unit keeps costs under $80. [Raspberry Pi Foundation, 2024]

How do modern gateway modules affect OBD-Pi?

Many 2018+ vehicles employ secure gateways that block third-party diagnostic frames. Without authenticated tokens, the Pi sees only limited PIDs. Spanish user notes gateways are “protected” and extra CAN buses exist. [Elektroda, luzmaig71919, post #21066040]
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