J1708 not working

[deputylynch]

I have a ScanGauge that works perfectly fine when plugged into my j1708 under the dash.

When I try to use the j-1708 in the outside compartment underneath the driver seat all I receive is the battery voltage and no other information.

Is this normal or do I have a back connection outside?

This is on a 2005 Monaco Diplomat. 

[Dr4Film]

Are you sure it is the same data bus? My guess is that it is not and that's why you don't see the data you are expecting.

[deputylynch]

They're both J1708 connectors with 4 wires into them but the one outside is only sending voltage information. 

[Scotty Hutto]

On my 2006 Dip, the connector in the FRB only provides connection to the Bendix brake system and (I believe) the Allison ECM.  I think it’s a J1587 (?) interface, but the same connector as a J1708.  

Those connections are only available with the Bendix and Allison software and proper connectors to a PC. I don’t believe a scangauge will connect to them. 

[deputylynch]

Yes, after getting my camera and scanning the top of it that I couldn't see, It is for the brake system.

I feel anybody else reading this will have an answer without finding out the hard way like I did. 

Again a great forum!

Thank you!! 

Edited September 22, 2023 by deputylynch
Punctuation