Want to increase or lower your truck’s top speed? Freightliner trucks with Cummins or Detroit engines allow you to change the road speed governor—as long as you have the right diesel laptop and software.

Here’s how to adjust your truck’s speed governor without going to the dealer.

🛠 What You’ll Need:

• Diesel laptop scanner kit

• RP1210 adapter (like Nexiq USB-Link or Inline 6)

• Compatible software: Detroit DDDL, depending on your engine

• Truck parked with ignition on

🔄 Step-by-Step: Adjust Speed Governor

1. Plug in your adapter to the 9-pin port

2. Open your diagnostic software and connect to the ECM

3. Navigate to Vehicle or Parameter Settings

4. Locate the setting called:

   • “Maximum Vehicle Speed”

   • or “Road Speed Governor”

5. Change the value to your desired limit (example: 65 → 72 MPH)

6. Click Program or Write to ECM

7. Save changes and cycle the ignition

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⚠️ Note:

Some trucks may have a password-protected ECM or fleet lock. If so, contact tech support on how to remove the password.