View Full Version : Vehicle speed through diagnostic port

08-18-2007, 03:22 AM
Can vehicle speed be read through the diagnostic port on logic module cars? A smog referee told my friend that there was no speed shown but no 15 code is present. Is this normal?

08-18-2007, 05:42 AM
If you can, that would be news to me.

08-18-2007, 08:21 AM
You can. But, there's no special test code for it (I don't think). You have to get it in logging mode. I don't know if all the scan tools support it (DRB-I certainly would).

08-18-2007, 11:10 AM
My OTC 2k shows it.

08-18-2007, 11:18 AM
Yeah, I agree with a scan tool but the way I read it last night, could be tired, lol, was that the smog guys are saying you can by just using the test port, no scanner.

08-19-2007, 07:43 PM
I wasn't there but I think it's a pretty safe guess that a scanner was used. Could the computer (ND) possibly have the speed function disabled, for whatever reason?

08-20-2007, 08:13 AM
Possible, but not likely. What computer/year is it?

08-20-2007, 12:30 PM
'87 T2 logic module (in an L-body). Is there perhaps a different pin that should lead to the to the diagnostic port?

08-20-2007, 02:02 PM
No, it's a serial interface. If they get anything through the port, they should get it all.

'87 T2 LM - is that what they're using to setup the scanner? If they use the wrong engine VIN code, it could give the wrong data.

09-02-2007, 03:59 AM
I figured it out. We are using a non L-body computer with L-body wiring. The speed sensor wire was going to the wrong pin on the module. Once I changed that everything was good!:amen: