OBDII Specification/Odometer Read

**tahrens301** · 05-25-2006, 11:29 AM

Hi Folks, First time poster here.

1. Is the OBDII spec (from a command/data format) available on
the web somewhere?

2. Within that spec, is there a way to read the odometer? I don't
need to write to it. I know that most aftermarket boxes cannot
read the odometer, but as I understand it, the dealerships/service
people do have the capability, so I figure it's there somewhere.

I am planning to write my own code, so I just need the
software/hardware details.

Thanks!

Tim

**joeyoravec** · 05-25-2006, 01:11 PM

Originally Posted by tahrens301

Is the OBDII spec (from a command/data format) available on the web somewhere?

The SAE holds copyright, and they sell a PDF version of the OBD-II spec for around $50.

Originally Posted by tahrens301

Within that spec, is there a way to read the odometer? I don't need to write to it. I know that most aftermarket boxes cannot read the odometer, but as I understand it, the dealerships/service people do have the capability, so I figure it's there somewhere.

No, there's not a standard way to read the odometer. You would need to know the command for your specific make/model.

**Mechanic** · 05-26-2006, 10:12 PM

The protocols differ between manufacturers, but you can find the specifics for just about any of them on the web. Here is some good info on the J1850 VPW protocol used by GM:
J1850 VPW

**dwhite** · 06-03-2006, 10:33 PM

What kind of car do you have? We might have gotten it with our tools already?

**msamuels0** · 06-05-2006, 04:32 PM

Originally Posted by joeyoravec

No, there's not a standard way to read the odometer. You would need to know the command for your specific make/model.

Actually, there are standard PRN's in the J2178 spec for odometer readings... numbers 6031-6034

-Mark

**joeyoravec** · 06-05-2006, 06:30 PM

Understood, but J2178 seems like more of a "suggestion" than a standard. It surprises me when anything in that document lines up with reality. Do those PRNs actually line up with any production Ford or GM vehicles?