HD Pass-Thru Cable Power Reroute Guide

This guide provides instructions on how to reroute power to the HD Pass-Thru cables. These steps are necessary to resolve an issue with some heavy-duty vehicle diagnostic ports not providing consistent power to the device. Before you continue, please be sure you have properly tested the device-to-vehicle connection for possible blown fuses or a master battery cut-off switch.

Tools you will need include a digital multimeter, one razor knife, electrical tape, wire stripper, insulated crimper, wire cutter, three butt connectors, 16-18 AWG wire, one fuse holder, one 3-amp fuse, and five cable ties.

Installation Steps

The following steps provide an overview of the installation process:

  1. Cable Preparation.
  2. Circuit Connection.

  1. 1. Cable Preparation

    1. Disconnect the HD Pass-Thru cable from the vehicle’s diagnostic port and GPS device; nothing should be connected to the cable.
    2. Locate the section of cable marked with a dotted line box as shown below:
    3. Being careful not to cut into the wires, remove approximately 4 in. (10 cm.) of sheathing from this portion of the cable.
    4. Identify your cable type in the chart below and the wire color before cutting. Once cut, remove 1 in. of sheathing from the wire leading to the GPS device connection.
    5. Supplying power to the incorrect wire could cause serious device and vehicle damage. If the cable number is not present below, contact Technical Support for further assistance.

      RED Wire:

      • 5C909-2
      • 5C972-2

      Orange Wire:

      • 5C992-2
      • 5C973-2
      • 5C709M-2
      • 5C991M-2
      • 5C990M-2
      • 5C734M-2

    6. Using insulated crimpers, crimp a butt connector to the wire leading to replacement diagnostic port, and another to the wire leading to the GPS device before taping everything off and leaving the wire to the GPS device exposed.

    7. Remove 1 in. of sheathing from the inline fuse holder and butt connect the fuse holder to wire leading to the GPS device connection before taping off and cable tying connection.

  2. 3. Circuit Connection.

    1. Using a digital multimeter, locate a vehicle circuit which provides a continuous 12-24 VDC (+) whether the engine is On or Off OR whether or not the master cut-off is On or Off
    2. Once you have identified the constant power source, use the poke and wrap method to connect the inline fuse holder to this wire.
    3. Extend fuse holder wire if necessary, using the butt connectors and 16-18 AWG wire.

      1. On the fuse holder wire, strip off 1 1/2in. (4cm) of insulation, and twist the wire strands before poking it through the loop created for the Ignition source.
      2. Squeeze the loop shut, and tightly wrap the bare wire around the exposed wire at least three times.
      3. Fold the wire back, and generously wrap electrical tape around the connection, crossing over the insulation on both sides.
      4. Secure the connection with one zip tie directly over the wire-to-wire connection, and another zip tie on a stress loop created about 1in. (2.5cm) away from the connection.


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