If you are far away from home or any mechanical shop, suddenly, 4 MPH max speed until 73 miles pops up on your screen.
It’s an issue with the DEF DPF system of your vehicle.
If the diesel exhaust fuel is lower than 2-gallon, your diesel engine-driven vehicle will have a max speed limit issue.
- In the first stage, the max speed limit will be 65 mph until 73 miles meaning you can drive 73 miles at a max speed of 65 mph.
- In the second stage, the max speed limit will be reduced to 72 miles at a max speed of 55 mph.
- In the third stage, your vehicle’s max speed will be reduced to 4 mph until you drive 73 miles.
It is very risky to drive at 4 mph in the driveway.
Refill the tank with at least 2 gallons of DEF, or your vehicle will go to Limp Mode after 73 miles.
How to Clear Service DEF System Message Duramax [04 Methods]
There are 04 ways to clear the service DEF message, including adding DEF, scanning with an OBD scanner, disconnecting the negative battery terminal, and disconnecting the ABS sensor.
Let’s discuss these 04 methods in detail.
1. By Refilling DEF
DEF is not a fuel additive or fuel cleaner. It is stored in a separate tank behind the engine under the hood.
The tank is located on the front passenger seat under the hood, and the cap of the tank is blue.
The tank should be filled with DEF.
You have to refill the tank with DEF every 6000 miles.
If you don’t do so, the diesel exhaust fuel will reduce and cause the service DEF message.
DEF should not be less than 01-gallon.
Reduced diesel exhaust fluid will trigger your vehicle to go to the Limp Mode or Reduced Engine Power Mode.
Fill your 5.3-gallon tank with diesel exhaust fuel, and the clear Duramax service DEF system message will go away.
After filling the tank with DEF, start the truck and let it idle for 50 seconds.
Drive the vehicle for 5 minutes at low speed, Service DEF system message will go away.
Watch this video to learn how to add DEF to your Duramax.
If adding DEF doesn’t work, apply the second method-
2. By Resetting with a Scan Tool
You can reset the exhaust fluid system and clear the service DEF message in 07 simple steps with the help of a scan tool.
- Connect the scanner to the scan port adjacent to the dashboard. The plug-in point is located on the driver’s side.
- Find out the ‘Module setup’ by turning on the scanner.
- Click on the ‘Reductant’ fluid and go to the ‘Tank level reset’ option.
- Now reset the system, and the warning sign will be cleared.
- Now, go back to the ‘Reductant Data Reset’ and click the reset again.
- However, it will briefly show the warning and then clear again.
- And the system will reset successfully.
If you can’t scan and reset, go to a local mechanic and get help from them.
To learn how to diagnose the DEF or DPF problem, watch this YouTube video.
3. By Disconnecting the Battery Cables
According to some users, to remove the max speed limit 4 mph warning, Disconnect both negative battery cables for 30 seconds, and the system will reset, and the problem will be solved.
4. By Disconnecting the ABS/Speed Sensor
There is another method if the first one doesn’t work as planned.
- Just disconnect the ABS sensor. If it doesn’t work, then
- Disconnect the speed sensor located on the transfer case.
The speed limit will be gone for sure by applying this method.
Method 01 will work on all GM trucks, including Silverado and GMC; It will also work on Ford, Dodge Ram, Nissan, and all diesel trucks produced in or after 2011.
Your vehicle will come out from Limp Mode, and the max speed limit of 4 mph won’t be effective for you after disconnecting the ABS and Speed sensor.
This method will help you for a short time.
This will reset your system message and help you to go destination.
After this, I recommend taking the vehicle to the dealer or a mechanic for proper diagnosis.
Don’t forget to add DEF after every 6000 miles, or a service DEF system message will appear in your DIC, and your max speed will be reduced to 4 miles per hour.
If you forget to refill DEF and this problem occurs, you can temporarily apply these 02 methods to eliminate this issue.
But if possible, adding DEF is the first option that you should go for.