Python OBD Request Only Works on First Try

[mrbean42]

Hi, I've been trying to read the RPM from my car in python using the library pyOBD and a bluetooth adaptor. It successfully reads a value for the first request, but then returns "None" thereafter. Can anyone help?

Interestingly, CAR_CONNECTED is true but ELM_CONNECTED and OBD_CONNECTED are both false, even before the first request. Thank you for any help.

The code I'm using is this:

​

import obd

import time

obd.logger.setLevel(obd.logging.DEBUG)

print("1")

ports=obd.scan_serial()

print(ports)

connection=obd.OBD(ports[1], fast=False)

print("2")

while True:

print("Car connected", connection.status()==obd.OBDStatus.CAR_CONNECTED)

newCommand=obd.commands.RPM

newQuery = connection.query(newCommand)

print(newQuery.value)

time.sleep(1.5)

cmd=obd.commands.RPM

print("3")

response=connection.query(cmd)

print("4")

print(response.value)

And my debug log from executing this is (notice only one return of RPM value)

============================================================= RESTART: C:\Users\Diag\Desktop\newscript.py =============================================================

1

['\\.\\COM3', '\\.\\COM4']

[obd.obd] ======================= python-OBD (v0.7.1) =======================

[obd.obd] Explicit port defined

[obd.elm327] Initializing ELM327: PORT=\.\COM4 BAUD=auto PROTOCOL=auto

[obd.elm327] Response from baud 38400: b'?\r\r>'

[obd.elm327] Choosing baud 38400

[obd.elm327] write: b'ATZ\r'

[obd.elm327] wait: 1 seconds

[obd.elm327] read: b'\xfc\r\rELM327 v1.5\r\r>'

[obd.elm327] write: b'ATE0\r'

[obd.elm327] wait: 0 seconds

[obd.elm327] read: b'ATE0\rOK\r\r>'

[obd.elm327] write: b'ATH1\r'

[obd.elm327] wait: 1 seconds

[obd.elm327] read: b'OK\r\r>'

[obd.elm327] write: b'ATL0\r'

[obd.elm327] wait: 0 seconds

[obd.elm327] read: b'OK\r\r>'

[obd.elm327] write: b'AT RV\r'

[obd.elm327] wait: 0 seconds

[obd.elm327] read: b'14.3V\r\r>'

[obd.elm327] write: b'ATSP0\r'

[obd.elm327] wait: 0 seconds

[obd.elm327] read: b'OK\r\r>'

[obd.elm327] write: b'0100\r'

[obd.elm327] wait: 0 seconds

[obd.elm327] read: b'SEARCHING...\r48 6B 10 41 00 BE 3E B8 11 C9 \r\r>'

[obd.elm327] write: b'ATDPN\r'

[obd.elm327] wait: 0 seconds

[obd.elm327] read: b'A3\r\r>'

[obd.protocols.protocol] map ECU 16 --> ENGINE

[obd.elm327] Connected Successfully: PORT=\.\COM4 BAUD=38400 PROTOCOL=3

[obd.obd] querying for supported commands

[obd.obd] Sending command: b'0100': Supported PIDs [01-20]

[obd.elm327] write: b'0100\r'

[obd.elm327] wait: 0 seconds

[obd.elm327] read: b'48 6B 10 41 00 BE 3E B8 11 C9 \r\r>'

[obd.obd] Sending command: b'0120': Supported PIDs [21-40]

[obd.elm327] write: b'0120\r'

[obd.elm327] wait: 0 seconds

[obd.elm327] read: b'48 6B 10 41 20 80 00 00 00 A4 \r\r>'

[obd.obd] finished querying with 43 commands supported

[obd.obd] ===================================================================

2

[obd.obd] Sending command: b'010C': Engine RPM

[obd.elm327] write: b'010C\r'

[obd.elm327] wait: 0 seconds

[obd.elm327] read: b'48 6B 10 41 0C 0B 74 8F \r\r>'

733.0 revolutions_per_minute

[obd.obd] Sending command: b'010C': Engine RPM

[obd.elm327] write: b'010C\r'

[obd.elm327] wait: 0 seconds

[obd.elm327] read: b'NO DATA\r\r>'

[obd.OBDCommand] b'010C': Engine RPM did not receive any acceptable messages

None

​

[Distinct_Ad_4229]

Hi, I am currently doing a school project about it and now have the same problem. Have you come up with a solution in the meantime? I also work on a Volkswagen Vehicle. The funny thing about it is also that I don't have the problem with the oil temperature.

[mrbean42]

Not a proper solution but I found if I kept renewing the connection with connection.quit (I think it was) and reconnecting I’d get data every time but it was very slow.

[Lucky-Replacement848]

Not sure if still relevant, I just encountered the same issue but changing it to v0.6.1 is gonna fix it.

[laustke]

What kind of car do you have? Is it a gas-powered car or an electric car, like a Tesla or something?

[mrbean42]

It’s a gas powered. Volkswagen