HOW TO INSTALL CUMMINS OBD / CSP SOTF

Tools You’ll Need

Trim tool or flathead screwdriver
Flashlight
Zip ties
Drill + step bit (only if adding a new switch hole)

No battery disconnect required for OBD SOTF (but it won’t hurt if you want to)

What the OBD / CSP SOTF Does (Quick Explanation)

Uses the OBD-II communication port to switch tunes
Common on 07.5–2021 Cummins
Allows switching while driving (with rules)
Requires OBD/CSP-enabled tuning

Step-by-Step Installation

1. Locate the OBD-II Port

Driver’s side
Under the dash, left of the steering column

2. Plug in the OBD SOTF Cable

Plug the OBD connector from the SOTF harness directly into the factory OBD-II port
Make sure it seats fully

This cable does not replace a bypass cable
On 2018+ trucks, SGW bypass is still required for tuning access

3. Route the Switch Wiring

Run the switch wire up behind the dash
Keep it away from:
- Pedals
- Steering shaft
- Parking brake

4. Mount the SOTF Switch Inside the Cab

Common mounting locations:

Lower dash panel
Kick panel
Center console
Factory blank switch panel

5. Secure the Wiring

Zip-tie excess wiring
Ensure nothing can snag or rub

6. Verify Operation

Key ON (engine OFF)
Rotate the switch through all positions
Start engine and confirm:
- No warning lights
- Normal idle

How to Use the OBD / CSP SOTF (IMPORTANT)

You can switch tunes while driving
Do NOT switch under heavy throttle

Safe switching conditions

Idle
Light throttle
Steady cruise

Important Notes (READ THIS)

OBD SOTF does nothing without proper tuning
Switching too fast or under load can cause:
- Limp mode
- Communication faults
On 2022+ Cummins, OBD SOTF is NOT recommended
👉 CCV SOTF is the correct option instead

Quick Troubleshooting

No tune change

CSP/OBD SOTF not enabled in tuning
Wrong tune slot order

Truck goes into limp

Switch changed under throttle
Tuning mismatch

OBD port loose

Secure harness with zip ties to prevent vibration