DEF Emulator + OBD Reset Installation Instructions
This instruction is for installing the DEF/SCR emulator and clearing DEF-related warnings on 2023 and newer Mercedes Sprinter with the OM654 2.0L diesel engine.
The installation consists of three main steps:
- 1. Disconnect the SCR control unit
- 2. Connect the DEF emulator
- 3. Clear the fault codes using the OBD Reset module
Package Contents
Your package includes:
- DEF/SCR Emulator
- OBD Reset module
The DEF/SCR emulator is installed permanently in the vehicle.
The OBD reset module is used only to clear stored DEF / AdBlue errors and start countdown messages after the emulator is installed.
Before Starting
Before starting the installation, read the full instructions from start to finish.
You will need the following tools:
- Flat screwdriver
- Small flat screwdriver
- 10 mm wrench or socket
- Hex key / Allen key
Step 1 — Disconnect the SCR Control Unit
Before installing the emulator, the original SCR control unit must be disconnected.
Some plastic trim needs to be removed to access the SCR control unit connector. Do not force the plastic parts or connectors.
For this step, please watch the separate video instruction:
How to Access and Disconnect the SCR Unit
Once the SCR control unit connector is disconnected, continue with the emulator wiring.
Step 2 — Connect the DEF Emulator
The emulator has three wires that must be connected to the vehicle:
- 1. Power wire
- 2. Ground wire
- 3. NOx wire
Make sure the ignition is OFF before connecting the wires.
Connect the Ground Wire
Photo 1A: Ground point location
Photo 1B: Ground wire installed under the bolt
Connect the emulator ground wire to the ground point shown in the photos.
You will need a wrench or socket to remove the bolt completely.
The exact wrench/socket size is 10mm.
To connect the ground wire:
- 1. Locate the ground point shown in the photo.
- 2. Remove the bolt completely using the correct wrench or socket.
- 3. Place the emulator ground wire terminal under the bolt.
- 4. Install the bolt back into place.
- 5. Tighten the bolt securely.
- 6. Make sure the terminal has direct contact with clean metal.
A weak or loose ground connection may prevent the emulator from working correctly.
Do not connect the ground wire to plastic parts, painted surfaces, or any loose metal bracket. The ground wire must be connected to a solid metal ground point.
Connect the Power Wire
Photo 2A: Fuse location in the fuse box
Photo 2B: Power wire installed in the fuse slot
Connect the emulator power wire to the fuse box slot shown in the photos.
The required fuse slot is located in the fuse box, third position down from the upper right corner.
The exact fuse number will be provided separately: Fuse #59.
To connect the power wire:
- 1. Locate the required fuse slot in the fuse box.
- 2. Carefully remove the original fuse using a flat screwdriver.
- 3. Insert the removed fuse into the fuse tap on the emulator power wire.
- 4. Insert the emulator power wire with the fuse tap back into the same fuse slot.
- 5. Make sure the fuse tap is fully seated and the wire is secure.
The emulator must receive stable power when the ignition is ON.
Do not force the fuse tap into the slot. If it does not fit easily, check the position and orientation before continuing.
Disconnect NOx Sensors and Connect the NOx Wire
Photo 3A: NOx connector block location
Photo 3B: NOx connector block before disconnecting the sensors
Photo 3C: NOx connector block after disconnecting NOx #2 and NOx #3
Before connecting the final emulator wire, you need to access the NOx sensor connector block.
The NOx sensor connectors are installed in the connector block shown in the photos.
You need a small flat screwdriver to release the connector locks and disconnect the wires carefully.
To complete this step:
- 1. Locate the NOx connector block shown in Photo 3A.
- 2. Remove or release the connector block so you can access the connectors properly.
- 3. Disconnect NOx sensor #2 from position 2 in the connector block.
- 4. Disconnect NOx sensor #3 from position 5 in the connector block.
- 5. Connect the final emulator wire to any available connection point in this area, as shown in the photo.
- 6. Make sure the connection is secure.
After disconnecting NOx #2 and NOx #3, their connectors should remain unplugged.
Do not disconnect NOx sensor #1 from position 1. The emulator does not emulate NOx sensor #1.
Check the Emulator LED Status
After connecting the emulator and disconnecting the NOx sensor connectors, start the engine and check the LED light on the emulator.
The LED will blink in a repeating pattern. Count the number of blinks before the pause.
LED Status Meaning
-
1 blink + pause
The connection is correct. NOx #2 and NOx #3 are disconnected properly. You can continue to the OBD reset step.
-
2 blinks + pause
NOx #2 is still connected or the connectors may be mixed up.
-
3 blinks + pause
NOx #3 is still connected or the connectors may be mixed up.
If the Emulator LED Shows 2 or 3 Blinks
If the LED blinks 2 or 3 times before the pause, do not continue with the OBD reset yet.
First, check the NOx connector block again:
- 1. Turn the ignition OFF.
- 2. Check that NOx sensor #2 is disconnected from position 2.
- 3. Check that NOx sensor #3 is disconnected from position 5.
- 4. Make sure the emulator wire is connected correctly.
- 5. Turn the ignition ON again and check the LED.
If the LED still shows 2 or 3 blinks, the NOx connectors may have been previously mixed up or installed in different positions.
How to Find the Correct NOx Connections
To avoid confusion, change only one connector at a time.
Recommended method:
- 1. Take a clear photo of the current connector positions before making any changes.
- 2. Mark the disconnected connectors with tape or labels.
- 3. Move only one connector or connection at a time.
- 4. Turn the ignition ON and check the emulator LED after each change.
- 5. If the LED changes to 1 blink + pause, the connection is correct.
- 6. If the LED still shows 2 or 3 blinks, turn the ignition OFF and try the next connector position.
Do not move several connectors at once. If you change multiple connectors at the same time, it will be difficult to understand which change fixed the problem.
The correct result is always:
1 blink + pause
Only continue to the OBD reset step after the emulator LED shows 1 blink + pause.
Step 3 — Clear the Errors with the OBD Reset Module
After the emulator LED shows 1 blink + pause, the emulator connection is correct.
Now you need to clear the stored DEF/AdBlue errors and start countdown messages using the OBD reset module.
Turn the Ignition ON
Turn the ignition ON, but do not start the engine.
- 1. Make sure your foot is NOT on the brake pedal.
- 2. Press the Start/Stop button two times.
- 3. The dashboard should turn on completely.
Wait 20 Seconds
After turning the ignition ON, wait about 20 seconds before plugging in the OBD module.
This allows the vehicle control systems to wake up fully before the reset starts.
Plug in the OBD Module
Plug the OBD reset module into the diagnostic port under the steering wheel.
Press the module firmly into the OBD port to make sure it has good contact.
A weak connection may interrupt the reset process.
Watch the LED on the OBD Module
Watch the LED light on the OBD module.
During normal operation, the LED should blink in a repeating pattern:
1 blink + pause
The Reset process may take up to 5 minutes.
When the LED light turns off, the reset process is complete.
After the LED turns off:
- 1. Remove the OBD module from the diagnostic port.
- 2. Turn the ignition OFF.
- 3. Start the engine.
If the OBD Reset Does Not Complete
If the OBD module LED keeps blinking for more than 5 minutes or if the LED shows:
2 blinks + pause
or
3 blinks + pause
the reset did not complete successfully.
Remove the OBD module from the diagnostic port and send us the LOGFILE from the OBD Reset module.
Please watch this video instruction on how to find and send the LOGFILE:
How to find and send the LOGFILE
Start the Engine and Check the Dashboard
Start the engine and check the dashboard.
The Check Engine light and Starts Remaining message should disappear.
In some cases, you may need to repeat the OBD reset process 1–2 more times to clear all stored messages completely.
To repeat the reset:
- 1. Turn the ignition ON by pressing the Start/Stop button two times without pressing the brake pedal.
- 2. Wait 20 seconds.
- 3. Plug in the OBD module and press it firmly into the port.
- 4. Watch the LED on the OBD module.
- 5. When the LED turns off, remove the OBD module.
- 6. Turn the ignition OFF.
- 7. Start the engine and check the dashboard again.
If the Warning Is Still Displayed
If the Check Engine light or Starts Remaining message is still displayed after several reset attempts, please send us the LOGFILE from the OBD Reset module and watch this video instruction on how to find and send the log file:
How to find and send the LOGFILE
Full Installation Video: How to install DEF Emulator
NEED HELP BEFORE ORDERING?
Message us — we respond within a few hours.
