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This guide covers how to use the AdBlue (DEF) Counter Reset module on 2019–2022 Mercedes Sprinter vans with OM651 or OM642 diesel engines. It explains DEF preparation, ignition and LED checks, the reset process, what to expect if the DEF fault remains, and when to send a LOGFILE for support.
This guide explains how to use the OBD module on a 2019–2026 Mercedes Sprinter with a 2.1L OM651, 3.0L OM642, or 2.0L OM654 diesel engine.
Your package may include:
The AdBlue Block Reset microSD card is already installed in the OBD module.
Before starting the installation, fill the DEF / AdBlue tank to 100%.
If the tank is around 70–90%, top it off to full.
Do not overfill the tank to the neck. Overfilling may cause the ultrasonic level sensor to read incorrectly.
Turn the ignition ON, but do not start the engine.
To turn the ignition ON:
Do not start the engine during the OBD module procedure unless the instruction specifically tells you to start it.
The OBD module has a small LED indicator.
After plugging the module into the OBD2 port, the LED will turn on and start blinking.
You must watch the LED during the procedure.
Do not remove the module while the LED is blinking normally.

If the DEF system problem is not repaired, DEF / AdBlue errors may return immediately after the reset. A new start countdown may appear again after about 50 miles, and the vehicle may show a new 10 Starts Remaining message.
You can use the OBD module to reset the countdown again and keep the van drivable for some time. However, the original DEF system problem must still be diagnosed and repaired.
Turn the ignition ON, but do not start the engine.
Press the Start/Stop button two times without pressing the brake pedal. The dashboard should turn on completely.
After turning the ignition ON, wait about 30 seconds.
This allows the vehicle control modules to wake up fully.
Plug the OBD module into the OBD2 port under the dashboard.
Press the module firmly into the port to make sure it has good contact.
Watch the LED on the OBD module.
The module is working while the LED is blinking normally. Do not remove the module during this process.
The reset process usually takes 2–4 minutes.
When the LED stops blinking or turns off, the reset is complete.
Remove the OBD module from the OBD2 port.
Start the engine and check if the Remaining Starts message has disappeared.
If the message is still displayed, repeat the reset process 1–3 more times.
If the message still does not clear, send us the LOGFILE from the OBD module.


How to contact us, what to send for faster help, and how we troubleshoot issues remotely
Follow a simple checklist before you start: power, DEF level, PC tools, and radio/display notes.