obd2, fuel sensor, odometer
 

Hello,
Does anyone know if fuel sensor data and odometer data is available thru the obd2 interface? It would be a big undertaking, but if this info's available at the obd2 interface, a realtime MPG display could be created. If it's not available at the obd2 interface, is it available in some known-format at the instrument cluster?

Thanks,
Don Cab

excellent.... i am working on a similar project!
i didnt even think about accessing via OBDII,
i read that the fuel gauge is a resistor type deal, so i was going to use a PIC microprocessor with Analog to Digital conversion to estimate the fuel in the tank, and the odometer/trip meters are digital, so im pretty sure those would be easy to interface up to the PIC. but my PIC programmer broke a month ago and i have no funds to get a new one so the project is on hold :(

http://www.smokinmhz.com/mazda/


if anyone comes up with something, let us know! :)

Hey,
Good to hear you're using a PIC microcontroller. I've been thinking of something I can do w/ one too. For starters, I think I'll just interface a LM35 (linear temp sensor) into the A2D of the PIC for indoor temperature.

I haven't gotten enough info on the OBD2 or the fuel sensor to think I can complete this idea, so it's on hold for me, for now...

-Don Caballero

Haha do any of you know how to make milege disappear? lol

um..not interested in finding this info out. :)

It may be a little easier than going through the OBD. Just measure the fuel pressure and fuel injector pulse width to calculate actual fuel usage.

...fuel pressure...hrm okay that shouldnt be too hard...but injector pulse width? wtf? how???

Injector pulse width... Basically the computer sends a 12vdc signal to the injectors to control fuel flow. They are either on or off. No in between. The computer will turn them on anywhere from 1 to 100 milliseconds during the intake stroke to provide the correct amount of fuel flow. If you know how long the injectors are on, how much fuel pressure you have and the rated flow of the injector you can figure fuel usage.

I am really interested in exploring ODBII access to various data. Probably it is my professional deviation - I am computer programmer.
Do you know where I can get information about Mazda specific ODBII codes? Is it included in any Mazda manuals? Generic codes are easy to find on the Internet, so I am not interested in them.
Did any of you try to use ELM323 for OBDII access?
Info about the chip is provided at:
http://www.elmelectronics.com
The chip is really inexpensive. (The price is in Canadian $ as I think)
Thank you for any answers.

Jan

Fuel sensor data and tach/MPH readings are available via OBDII, however ODO is not.

Jan, I have used the ELM chip to pull OBD data before. I also wrote a GUI in C++ as well that pretty much automated all of the data retrieval (i'll be damned if i didn't lose it tho, I still have some stuff). The ELM chips are very easy to interface...basic serial RS232 communication.

very very interesting.

what exactly can you tell from the fuel sensor data?

uuuuuhhhhhhh... what? I don't get it! HEHEHE!

Check out this page for OBD II PIDs:

OBD Mode 1 and 2 PIDs

Note, these aren't trouble codes. These are PIDs (Parameter Identification) that provide real time info as to what's happening while the car is running.

okay for fuel system, you can see if its closed system, or open system, correct?

i m not sure i understand how to use this fuel information provided by ODBII to calculate MPG.

The OBDII system doesn't provide a flow rate of the fuel, it just monitors the status of the fuel system.


FYI: Looking through your website that you provided, I noted that you plan to use the Dinsmore digital compas. I just want to say that that has to be the most simple and effective device that I've ever used. It's very reliable. If you have any questions on the system that you are putting together, feel free to drop me a line for any questions or status updates. I built a similar system as my senior project in college (Mobile Navigation System). I'd be interested to know how yours comes together. Awsome job on that display.