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Debug Output

If python-OBD is not working properly, the first thing you should do is enable debug output. The following line enables console printing:

obd.debug.console = True

Here are some common logs from python-OBD, and their meanings:


Successful Connection

[obd] ========================== python-OBD (v0.4.0) ==========================
[obd] Explicit port defined
[obd] Opening serial port '/dev/pts/2'
[obd] Serial port successfully opened on /dev/pts/2
[obd] write: 'ATZ\r\n'
[obd] wait: 1 seconds
[obd] read: 'ATZ\rELM327 v2.1\r'
[obd] write: 'ATE0\r\n'
[obd] read: 'ATE0\rOK\r'
[obd] write: 'ATH1\r\n'
[obd] read: 'OK\r'
[obd] write: 'ATL0\r\n'
[obd] read: 'OK\r'
[obd] write: 'ATSPA8\r\n'
[obd] read: 'OK\r'
[obd] write: '0100\r\n'
[obd] read: '7E8 06 41 00 FF FF FF FF FC\r'
[obd] write: 'ATDPN\r\n'
[obd] read: 'A8\r'
[obd] Connection successful
[obd] querying for supported PIDs (commands)...
[obd] Sending command: 0100: Supported PIDs [01-20]
[obd] write: '0100\r\n'
[obd] read: '7E8 06 41 00 FF FF FF FF FC\r'
[obd] Sending command: 0120: Supported PIDs [21-40]
[obd] write: '0120\r\n'
[obd] read: '7E8 06 41 20 FF FF FF FF FC\r'
[obd] Sending command: 0140: Supported PIDs [41-60]
[obd] write: '0140\r\n'
[obd] read: '7E8 06 41 40 FF FF FF FE FB\r'
[obd] finished querying with 93 commands supported
[obd] =========================================================================

Unresponsive ELM

[obd] ========================== python-OBD (v0.4.0) ==========================
[obd] Explicit port defined
[obd] Opening serial port '/dev/pts/2'
[obd] Serial port successfully opened on /dev/pts/2
[obd] write: 'ATZ\r\n'
[obd] wait: 1 seconds
[obd] __read() found nothing
[obd] __read() found nothing
[obd] __read() never recieved prompt character
[obd] read: ''
[obd] write: 'ATE0\r\n'
[obd] __read() found nothing
[obd] __read() found nothing
[obd] __read() never recieved prompt character
[obd] read: ''
[obd] Connection Error:
[obd]     ATE0 did not return 'OK'
[obd] Failed to connect
[obd] =========================================================================

This is likely a problem with the serial connection between the OBD-II adapter and your computer. Make sure that:

  • bluetooth devices have been paired properly
  • you are connecting to the right port in /dev (or that there is any port at all)
  • you have the correct permissions to write to the port

You can use the scanSerial() helper function to determine which ports are available for writing.

import obd

ports = obd.scanSerial()       # return list of valid USB or RF ports
print ports                    # ['/dev/ttyUSB0', '/dev/ttyUSB1']

Unresponsive Vehicle

[obd] ========================== python-OBD (v0.4.0) ==========================
[obd] Explicit port defined
[obd] Opening serial port '/dev/pts/2'
[obd] Serial port successfully opened on /dev/pts/2
[obd] write: 'ATZ\r\n'
[obd] wait: 1 seconds
[obd] read: 'ATZ\rELM327 v2.1\r'
[obd] write: 'ATE0\r\n'
[obd] read: 'ATE0\rOK\r'
[obd] write: 'ATH1\r\n'
[obd] read: 'OK\r'
[obd] write: 'ATL0\r\n'
[obd] read: 'OK\r'
[obd] write: 'ATSPA8\r\n'
[obd] read: 'OK\r'
[obd] write: '0100\r\n'
[obd] read: 'SEARCHING...\rUNABLE TO CONNECT\r'
[obd] write: 'ATDPN\r\n'
[obd] read: '0\r'
[obd] Connection Error:
[obd]     ELM responded with unknown protocol
[obd] Failed to connect
[obd] =========================================================================

This is a connection problem between the ELM adapter and your car. Make sure that you car is powered, and that the electrical connection between the adapter and your car's OBD-II port is sound.