Geotab Support Forum

Can anybody explain to me how to tell what type of engine diagnostic connection I need? Is there a way to tell by looking at the connector in the truck? I need to know whether it is a J1708 or J1939. Thanks.

Hello,

The below forum post should be considered a Guideline and not a rule. Depending on the manufacturer, the transition year from J1708 to J1939 may vary.

J1939 vehicles have a 9 pin deutsch connection, while J1708 vehicles may have either a 6 pin or a 9pin deutsch connection.

In General,

J1939 over CAN should be considered for 2007 and newer model vehicles

J1708 should be considered for 1996 to 2006 model medium and heavy duty diesel trucks.
• For model year 1996 – 2000, consider J1708 - 6 pin harness
• For model year 2000 - 2006 consider J1708 - 9 pin harness
• Note that 2000/1 models may be 6 or 9 pin depending on the engine – be prepared and order spare harnesses of each type.

In addition, on the last page of the GO4 Installation guide, you can see a list of pinouts for J1939 and J1708. When looking at the connector inside the truck, you may be able to see which pins are populated. Note in 2006/2007, some vehicles had both J1708 and J1939 pins populated inside the 9 pin connector.

GO4 Installation Guide

I have a question regarding this, is there a difference in the actual Geotab controller when a 6 pin or 9 pin harness is used? What I mean is say that I have a GO4 unit in a 6pin vehicle then I move it to a 9 pin will it work fine? or if I mix two up?

For J1708, the same Geotab unit can be used with either a 6 Pin or a 9 Pin connector. You can safely move the same unit from a 6pin vehicle, to a 9pin vehicle by changing only the J1708 harness.

For J1939, there is onyl one connector type( 9 pin). You cannot use a J1939 9pin connector with a J1708 unit and vise versa. The J1708 9-pin and J1939 - 9 pin connectors look identical except for the pinouts. In addition, The J1708 and J1939 Geotab units are two separate Geotab units.

I am unable to get to the GO4 Installation Guide. I need to see the pinouts for both the J1708 9-pin and the J1939. Would you be able to send me that?

The Installation guide is available on our downloads page http://www.geotab.com/support.aspx
However, the GO4v3 Installation guide does not include pinout diagrams, for the pinout diagrams you will need the Protocol Identification document which is also available in that same downloads page.