Subject: Re: Car speed conversion error
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NNTP-Posting-Date: Mon, 25 Nov 2002 21:54:38 EST
Organization: Prodigy Internet http://www.prodigy.com
Date: Tue, 26 Nov 2002 02:54:38 GMT
On 25 Nov 2002 07:37:09 -0800, email@example.com (Amy) wrote:
>The SAE standard I have for OBD II is SAE J1979. In sections 5.3 to
>5.5 they have PID tables for various modes.
>There is no mandatory PID for odometer reading.
OK this is for legislated E/E diagnostic test modes for emissions
Any PID can be requested using J2190.
This describes emissions and non emissions related messages can be
used with a diagnostic serial data link such as described in SAE J1850
or ISO 9141-2.
>I am not sure for the case of CAN protocol. But for J1850, they do
>provide odometer information in three parameters:
>- odometer - English, high resolution (1 bit = 1/8000 mile)
>- odometer - English, low resolution (1 bit = 1/10 mile)
>- odometer - metric, 1 bit = 1/64 km
>The thing is I am not sure if all three parameters would be present on
>the bus in most cars. I know mostly likely, a car in States would have
>odometer reading in miles. But would it have both the high-resolution
>or low-resolution parameters, I don't know. And in my project,
>accuracy is a concern. I need to use parameter with high resolution,
>whether it's odometer or vehicle speed.
>As for CAN protocol, does anyone know which SAE or ISO standards I
>need to find parameter definitions in terms of the parameter's
>transmission rate, data length, PDU format, PDU specific, etc?
Asked and answered my times in rec.autos.tech
The correct documents can be obtained from SAE www.sae.org and ISO
>Thanks a lot!