Description and Operation of the Diesel Exhaust Fluid Dosing
System
The Diesel Exhaust Fluid (DEF) doser is mounted to the Aftertreatment Device (ATD). The primary function of the
dosing unit is to directly inject a fine spray of DEF into the ATD via an electronically controlled valve. The doser is
controlled by the ACM, which controls the amount of DEF injected into the exhaust catalyst. The DEF pump
module maintains 10 bar (145 psi) of DEF pressure to the doser inlet fitting (1).
The constant supply of DEF is used to cool the dosing unit. The cooling operation is critical, and may never be interrupted or stopped during engine operation. There is a final filter located inside the doser to remove any remaining unfiltered debris. The DEF pressure is monitored by a pressure sensor located inside the doser housing. The remaining DEF is returned to the supply tank through the doser outlet fitting (2).
Removal of the Diesel Exhaust Fluid Dosing Unit
Remove as follows:
NOTICE
Wait at least five minutes after shutting down the engine to disconnect the battery ground
cable. Disconnecting the battery ground cable too soon could prevent post-run cooling of
the DEF dosing unit after the engine is shut down.
1. Shut off engine and apply the parking brake, chock the wheels, and perform any other applicable safety
steps.
2. Disconnect the batteries. Refer to OEM procedures.
3. If necessary, remove the side fairing. Refer to OEM procedures.
4. Disconnect the DEF pressure and return lines from the dosing unit.
5. Disconnect the DEF doser electrical connector (2)
NOTICE
The DEF dosing unit bolts and gasket are one-time-use items.
6. Remove the three bolts (1) (See figure above) securing the DEF dosing unit to the mounting plate and
discard bolts.
7. Remove the DEF dosing unit and discard doser gasket.
Installation of the Diesel Exhaust Fluid Dosing Unit
Install as follows:
NOTICE
The Diesel Exhaust Fluid (DEF) doser gasket and bolts are one-time-use items. Over
torqueing the DEF doser bolts will crush the gasket, causing exhaust leaks.
1. Install a new gasket with the gasket legs facing outward.
2. Install the DEF dosing unit to the mounting plate by installing the three new bolts (1). Torque to 10 N·m (7
lb·ft).
3. Connect the DEF doser electrical connector (2) (see figure above).
4. Connect the DEF pressure and return lines to the DEF dosing unit.
5. Connect the batteries.
Note : Opening the DEF system can cause DEF from the lines to drain back to the DEF tank. Performing an ADS
Priming Function will prime the DEF system and restore proper system operation.
6. Using DiagnosticLink , perform an ADS Priming Function to prime the DEF system and check for leaks.
7. If removed, install the side fairing. Refer to OEM procedures.
Removal of the Diesel Exhaust Fluid Dosing Unit Inlet Screen
Remove as follows:
1. Shut off engine and apply the parking brake, chock the wheels, and perform any other applicable safety
steps.
2. Disconnect the batteries.
3. Remove fairings to gain access to the dosing unit (if present).
4. Disconnect the Diesel Exhaust Fluid (DEF) inlet and outlet lines from the dosing unit.
5. Remove and discard the two bolts (1) fastening the DEF flange (2) to the dosing unit (5) and remove DEF
flange (2).
6. Remove the two DEF flange connectors (3) and discard.
Note : DEF doser inlet screen (4) is pressed, not screwed, into bore.
7. Remove the DEF doser inlet screen (4).
Installation of the Diesel Exhaust Fluid Dosing Unit Inlet Screen
Install as follows:
1. Install the Diesel Exhaust Fluid (DEF) dosing unit inlet screen (3).
2. Install two new DEF flange connectors (4) into DEF flange (5).
3. Install the DEF flange (5) to the DEF dosing unit (2).
4. Install two new bolts (1) to fasten DEF flange and torque to 7 to 8 N·m (5 to 6 lb·ft).
5. Connect the DEF supply and return lines to the DEF dosing unit.
6. Connect the batteries.
Note : Opening the DEF system can cause DEF from the lines to drain back to the DEF tank. Performing an ADS
Priming Function will prime the DEF system and restore proper system operation.
7. Using DiagnosticLink , perform an ADS Priming Function to prime the DEF system and check for leaks.