Get Current Gear with ODB II

**chrisstavrou** · 11-15-2009, 05:08 AM

Hi all,
i just started interacting using OBDII protocol with my car (RAV4) through a VB program i did.

I managed to find out the standard PIDs such as RPM, Speed etc but i have not managed to find anything related to current speed.

After some googling, i was pointed to the PID 19F5 but with no information on what mode it should be used.

Does anyone have any idea of how to get the current gear ?

Thanks in advance
Chris

**p2psmurf** · 11-15-2009, 05:53 AM

Current Speed: Pid 0D Current gear is not available, only manufacturer specific.
http://en.wikipedia.org/wiki/OBD-II_PIDs

**chrisstavrou** · 11-15-2009, 06:02 AM

Thanks for the link,
the info i found and it made me think its standard is this one

http://obdproject.com/OBD2Info/Specs/pidlist.htm

May be i should talk to the author.

**p2psmurf** · 11-16-2009, 03:11 AM

That's what I call an old and incomplete list. Even back in 1996 we started out with more standard pids than $1C. Any pids with 4-digit number is non-standard and manufacturer specific.

**malcom2073** · 11-16-2009, 05:40 AM

You could use speed and rpm to figure out what gear you're in. It would be fairly easy with a standard transmission. A bit tougher with an auto... but not entirely impossible.

**firstorbit84** · 11-16-2009, 07:25 AM

^^^ Ya that's exactly what I was thinking. It'd be easier if you knew the gear ratios and final drive.

**chrisstavrou** · 11-16-2009, 11:46 AM

Thanks for the comments,
as a final question can anyone let me know the formula that relates speed , rpm and gear ratio ?

**VegasGuy** · 11-16-2009, 12:23 PM

Originally Posted by chrisstavrou

Thanks for the comments,
as a final question can anyone let me know the formula that relates speed , rpm and gear ratio ?

I'm not sure that's going to work. The rpm can change depending upon engine load (up hill, down hill, pulling a heavy load) while the gear and speed remain the same. Probably get a general idea, but it's not going to be accurate under every circumstance. Besides, I thought the whole point of an automatic transmission was so you didn't have to worry about the gears?

VegasGuy

**chunkyks** · 11-16-2009, 12:52 PM

Spend a few minutes logging data, rpm and vss, in each gear. Draw out a chart of rpm/vss. The height at the long flat bits are the gear ratios. Write down those numbers.

Now go back and while you're driving, pick the rpm/vss ratio that's closest to your known gear. Done.

Of course, doing this automatically is a fair bit harder. My current plan is to [when I have time] do the ratios, use FFTs to throw away the high frequency stuff, and calculate the flat bits.

Gary (-;