Tools for interfacing with vehicle engine control units using the OBD-II protocol.
The On-Board Diagnostics II (OBD-II) standard is a mandatory requirement for all vehicles manufactured since 1997 in many countries. It specifies a number of protocols that manufacturers must implement for diagnostic scan tools to communicate with engine control units (ECU). These protocols are used for monitoring and troubleshooting vehicle drive trains, chassis and electrical systems. Implementing a hardware interface is relatively easy with a basic knowledge of electronics and one of the OBD interpreter kits available from popular electronics stores (See section 5).
Implemented with two processes, a graphical user interface and a communications server process.
-
GUI: GTK+3.0 user interface.
-
OBD Communications: a process that implements RS232 comms with the OBD-II interface and TCP/IP comms with the GUI.
-
Main Gauge Panel with OBD-II protocol drop down list, nine gauges, PID information and DTC code windows.
-
Auxilliary Gauge Panel.
-
PID Information and Search Panel.
-
Communications Log Panel.
1 - OBD-II as defined by the CARB
2 - OBD as defined by the EPA
3 - OBD and OBD-II
4 - OBD-I
5 - Not OBD compliant
6 - EOBD (Europe)
7 - EOBD and OBD-II
8 - EOBD and OBD
9 - EOBD, OBD and OBD II
10 - JOBD (Japan)
11 - JOBD and OBD II
12 - JOBD and EOBD
13 - JOBD, EOBD, and OBD II
14 - Reserved
15 - Reserved
16 - Reserved
17 - Engine Manufacturer Diagnostics (EMD)
18 - Engine Manufacturer Diagnostics Enhanced (EMD+)
19 - Heavy Duty On-Board Diagnostics (Child/Partial) (HD OBD-C)
20 - Heavy Duty On-Board Diagnostics (HD OBD)
21 - World Wide Harmonized OBD (WWH OBD)
22 - Reserved
23 - Heavy Duty Euro OBD Stage I without NOx control (HD EOBD-I)
24 - Heavy Duty Euro OBD Stage I with NOx control (HD EOBD-I N)
25 - Heavy Duty Euro OBD Stage II without NOx control (HD EOBD-II)
26 - Heavy Duty Euro OBD Stage II with NOx control (HD EOBD-II N)
27 - Reserved
28 - Brazil OBD Phase 1 (OBDBr-1)
29 - Brazil OBD Phase 2 (OBDBr-2)
30 - Korean OBD (KOBD)
31 - India OBD I (IOBD I)
32 - India OBD II (IOBD II)
33 - Heavy Duty Euro OBD Stage VI (HD EOBD-IV)
34-250 - Reserved
251-255 - Not available for assignment (SAE J1939 special meaning)
1 - SAE J1850 PWM (41.6 kbaud)(Ford)
2 - SAE J1850 VPW (10.4 kbaud)(GM, Isuzu)
3 - IS0 9141-2 (5 baud init, 10.4 kbaud)(Chrysler)
4 - ISO 14230-4 KWP2000 (5-baud init.)
5 - IS0 14230-4 KWP2000 (Fast init.)
6 - IS0 15765-4 CAN (11 bit ID, 500 kbaud)
7 - IS0 15765-4 CAN (29 bit ID, 500 kbaud)
8 - IS0 15765-4 CAN (11 bit ID, 250 kbaud)
9 - IS0 15765-4 CAN (29 bit ID, 250 kbaud)
A - SAE J1939 CAN (29 bit ID, 250 kbaud)
B - USER1 CAN (11 bit ID, 125 kbaud)
C - USER2 CAN (11 bit ID, 50 kbaud)
Note: From 2008 all vehicles must support Controller Area Network (CAN-Bus) protocols.
The SAE J1979 standard currently defines ten possible diagnostic test modes:
01 - show current data
02 - show freeze frame data
03 - show diagnostic trouble codes
04 - clear trouble codes and stored values
05 - test results, oxygen sensors
06 - test results, non-continuously monitored
07 - show pending trouble codes
08 - special control mode
09 - request vehicle information
0A - request permanent trouble codes
TODO:
Parameter identifiers represent values maintained by the ECU, most are sensor values obtained by monitoring the numerous drive train, chassis and body sensors on the vehicle. The PIDs are hexadecimal values encoded as ASCII characters for communication between ELM327 based OBD interpreters and the laptop/tablet/smartphone client device.
[PID] [Data Bytes] [Min Value] [Max Value] [Formula] [Description]
01 4 Bit Encoded (Monitor status since DTCs cleared)
04 1 0 100 100 / 255 * A (Calculated Engine Load)
05 1 -40 215 A - 40 (ECT Centigrade)
0A 1 0 765 3 * A (Fuel Pressure kPa)
0B 1 0 255 A (MAP Pressure kPa)
0C 2 0 16,383.75 (256 * A + B) / 4 (Engine RPM)
0D 1 0 255 A (Vehicle Speed)
0E 1 -64 63.5 (A / 2) - 64 (Timing Advance: degrees before TDC)
0F 1 -40 215 A - 40 (IAT Centigrade)
11 1 0 100 100 / 255 * A (Throttle Position %)
22 2 0 5177.265 0.079(256*A + B) (Fuel Rail Pressure)
23 2 0 655,350 10(256*A + B) (Fuel Rail Gauge Pressure)
2F 1 0 100 100 / 255 * A (Fuel Tank Level %)
45 1 0 100 100 / 255 * A (Relative Throttle Position %)
59 2 0 655,350 10(256*A + B) (Fuel Rail Absolute Pressure)
5A 1 0 100 100 / 255 * A (Relative Accelerator Pedal Position %)
5C 1 -40 215 A - 40 (Oil Temperature)
5E 2 0 3276.75 (256 * A + B) / 20 (Fuel Flow Rate L/h)
(Oil Pressure - manufacturer proprietary codes.) (Mode 22 PID 115C - GM)
[PID] [Data Bytes] [Description]
02 17 VIN - Vehicle Identification Number
0A 20 ECU Name
- ELM327 OBD Interpreter - https://www.elmelectronics.com/wp-content/uploads/2016/07/ELM327DS.pdf
- STN1110 OBD Interpreter - http://www.obdsol.com/solutions/chips/stn1110/
- Sparkfun Car Diagnostics Kit - https://www.sparkfun.com/products/10769
- Altronics OBD Interpreter Kit - http://www.altronics.com.au/p/k4065-obdii-automotive-interpreter-kit/
- Silicon Chip Magazine Feb 2010 Issue: https://www.siliconchip.com.au/
TODO:
- Lewis Van Winkle, TinyExpr Math Evaluator: https://github.com/codeplea/tinyexpr.git
- Teunis van Beelen, RS232 Serial Communications: https://www.teuniz.net/RS-232/
- Troy D. Hanson, UTHASH List/Map Data Structures: http://troydhanson.github.com/uthash/
- Jan Bodnar, GTK+ Tutorial and Example Code: http://zetcode.com/
apt install libgtk-3-dev
git clone https://github.com/dchad/OBD-Monitor.git
cd OBD-Monitor/src
make all
Make targets:
make all
make gui
make server
make simulator (for development and testing the GUI, simulates the server and ECU)
make utests (unit tests)
make ftests (server functional tests and logging when connected to an ECU, replaces GUI)
make stests (USB-Serial Port interface testing with a loopback cable)
To build with MSYS2 on Microsoft Windows download and install MSYS2 (www.msys2.org).
Open an MSYS2 terminal and install GTK+ as per the instructions here (www.gtk.org/download/windows.php).
Check that Git is installed and pull the OBD-Monitor source code.
Build with the command: make -f Makefile.win
INCLUDES=-I/mingw64/include/gtk-3.0 -I/mingw64/include/dbus-1.0 -I/mingw64/lib/dbus-1.0/include \
-I/mingw64/include/gio-win32-2.0/ -I/mingw64/include/cairo -I/mingw64/include/pango-1.0 \
-I/mingw64/include/harfbuzz -I/mingw64/include/pixman-1 -I/mingw64/include/freetype2 \
-I/mingw64/include/libpng16 -I/mingw64/include/gdk-pixbuf-2.0 -I/mingw64/include/glib-2.0 \
-I/mingw64/lib/glib-2.0/include -I/mingw64/include/atk-1.0
LIBS=-lm -lgtk-3.dll -lgdk-3.dll -lpangocairo-1.0.dll -lpango-1.0.dll -latk-1.0.dll -lcairo-gobject.dll \
-lcairo.dll -lgdk_pixbuf-2.0.dll -lgio-2.0.dll -lgobject-2.0.dll -lglib-2.0.dll -lwsock32
LIBDIRS=-L/mingw64/lib -L/mingw64/lib/gtk-3.0 -L/mingw64/lib/glib-2.0
Add /mingw64/bin to the PATH or gcc will do nothing and exit without reporting any errors!
ldd gtkapp.exe
ldd gtkapp.exe | grep '\/mingw.*\.dll' -o | xargs -I{} cp "{}" .
This command copies the dlls to the current directory.
Use the following procedure if problems occur with USB-RS232
interfaces such as the FTDI232 module on Linux:
Device Driver Downloads:
- FTDI232 devices: (https://www.ftdichip.com/FTDrivers.htm).
- CP2102 devices: (https://www.silabs.com/products/development-tools/software/usb-to-uart-bridge-vcp-drivers).
1. cd OBD-Monitor/src
make stests
2. Connect a wire between the USB-RS232 converter module transmit and
receive pins, then insert the module into a USB port.
3. Check the kernel module is loaded, for example:
dmesg | grep "FTDI"
4. Check for user read/write permission on the device.
ls -la /dev/ttyUSB0
sudo chmod a+rw /dev/ttyUSB0
or
chmod +s serial_test (may not work)
or
usermod -G dialout "user-name" (may not work)
5. Run the serial loopback test with an optional device name:
./serial_test ttyUSB0
or
./serial_test ttyACM0
or
./serial_test
6. If serial communications still not functioning then the
converter module may be faulty. Try swapping out the module,
Silicon Chip Magazine sell them for $5.00AUD plus postage.
(http://www.siliconchip.com.au/Shop/7/3437)
If serial interface confirmed working, but no communication with the OBD interpreter module:
-
Turn vehicle ignition OFF.
-
Connect the interpreter module to vehicle OBD socket.
-
Connect serial cable from the OBD interpreter module to laptop.
-
Turn vehicle ignition ON, but do not start vehicle.
-
Ensure interpreter module power LED indicators go ON.
-
On laptop:
cd OBD-Monitor/src
make server
make ftests
chmod +s obd_monitor_server
./obd_monitor_server 8989
./server_test
-
Output from server_test should indicate correct OBD protocol for the vehicle.
-
If "NO DATA" returned then the wrong OBD protocol has probably been selected by the interpreter auto search function.
-
Set the correct OBD protocol manually with:
./server_test protocol-number
Where protocol number is between 1 and C hexadecimal (see Section 4.2).
-
If still no data returned:
Open a serial terminal program such as moserial.
Select the serial port and default comms parameters.
Example: ttyUSB0, 9600 baud, 8 data bits, no parity, 1 stop bit.
Ensure line terminator option is set to carriage return "\r" character or new line and carriage return "\n\r".
Type the following command into the terminal input and press enter.
"ATDP"
This should return the currently set OBD protocol. If "NO DATA" is
returned then either the OBD interface or the ECU are faulty.
Other ELM327 or compatible interpreter commands to try:
"ATZ" - reset the OBD interpreter IC.
"ATI" - get OBD interpreter version ID.
"ATRV" - vehicle battery voltage.
"ATTP n" - try protocol number "n".
"09 02" - get vehicle VIN number.
"09 0A" - get ECU name.
"01 01" - get MIL (check engine light) status and number of diagnostic trouble codes set.
"03" - get a list of diagnostic trouble codes currently set.