HOW TO INSTALL CUMMINS BYPASS CABLE

CUMMINS CABLE (SGW) EZ LYNK / EFI / HP TUNERS 2019/2020 Star Connector

How the Bypass Cable Works

Most 2018+ Cummins trucks have a Security Gateway Module (SGW) built into the wiring that blocks tuning tools from directly accessing the ECM. The bypass cable reconnects the communication lines (CAN/EOBD) so your tuning tool sees the ECM normally.

Unlike SOTF (Switch-On-The-Fly) cables, this doesn’t go to a cabin switch — it stays under the dash or in the OBD area and can be left installed permanently.

Tools You’ll Need

  • Small pick or terminal release tool

  • Flathead screwdriver (optional)

  • Flashlight

  • Zip ties (optional)

Step-by-Step Installation

1. Turn Off the Truck

Ensure ignition is OFF and keys are out.

2. Locate the Bypass Connector

  • On 2018+ Cummins 6.7L (Ram), there’s a large white multi-pin connector above the OEM OBD-II port inside the driver’s footwell.

⚠️ Do not unplug the factory OBD-II port — you want the larger white connector above it.

3. Prep the Bypass Cable

  • Some cables are plug-and-play (just plug in).

  • Others (especially DIY bypass) may require de-pinning two CAN wires from the factory OBD-II plug and inserting them into the bypass harness.

4. Connect the Bypass Cable

Plug the bypass cable into the white SGW bypass slot in the harness above the OBD-II port.

  • The connector only fits one way — don’t force it.

  • Make sure it seats fully with the locking tab engaged.

5. Verify Connection

  • Wiggle the harness gently to ensure it’s secure.

  • Optional: zip-tie it up so it doesn’t hang down or pull.

6. Leave It Installed

Once installed, the bypass cable can stay in place permanently — the OBD-II port still works normally for diagnostics and scanning even after install.

 

Notes & Tips

📌 Why you need this
Without it, tools like EZ Lynk, EFI Live, HP Tuners, and similar tuning systems won’t be able to communicate with the Cummins ECM on 2018+ vehicles.

📌 It’s not a power or performance part
This cable doesn’t make power — it only unlocks communication so you can flash tunes or change tire size, remote start configs, etc.

📌 Permanent vs Temporary
Some brands are built to stay in the truck; others you can unplug after tuning. Check how your cable is manufactured.

 

Quick Troubleshooting

Truck won’t connect to tuner

  • Check bypass plug is fully seated

  • Make sure you’re using correct port above OBD-II

OBD-II still blocked

  • Some early bypass designs need CAN wires moved manually (if not pre-assembled)

Loose wiring under dash

  • Use zip ties to secure the harness so it doesn’t rattle or kink