Description and Operation of the Airless Dosing System Diesel
Exhaust Fluid Pump
In most applications, the Diesel Exhaust Fluid (DEF) pump module is mounted to a bracket located behind the
DEF tank. The DEF pump module draws DEF from the tank, filters it and pumps it under 10 bar (145 psi) of
pressure through a variable speed pump. The DEF pump pressure is controlled through the ACM via a pressure
sensor located inside the DEF doser. The following items are serviceable for the DEF pump: DEF inlet fitting (1),
DEF inlet filter screen (2), DEF outlet fitting (3), coolant inlet/outlet fitting (4), pressure relief valve (5), pressure
relief valve plug screw (6), and DEF pump main filter (7).
Removal of the Diesel Exhaust Fluid Pump Module
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 Diesel Exhaust Fluid (DEF) doser 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. Drain the cooling system.
4. Remove the four mounting bolts that secure the protective cover (1).
NOTICE
To disconnect a DEF line, push the line coupling in towards the male connector to move
the holding clip to the unlocked position, then compress the prongs of the holding clip
and pull the line off of the male connector. Failure to properly remove a DEF line can
result in damage to a line coupling or DEF port.
5. Disconnect the coolant inlet and outlet lines at the DEF pump.
6. Disconnect the DEF return line from the DEF header.
7. Disconnect the DEF inlet and outlet lines at the DEF pump.
8. Disconnect the electrical harness connectors.
9. Remove the nuts (2) and washers holding the DEF pump mounting bracket (3) to the DEF tank bracket (4).
10. Remove the DEF pump (1) from the mounting studs.
11. Remove the two bolts (5) that fasten the DEF pump to the mounting plate. See graphic above.
Inspection of the Diesel Exhaust Fluid Pump Module
Inspect as follows:
1. Inspect the DEF suction (1) and pressure (2) lines for blockages or crystalized DEF. If flushing is
necessary, Refer to section “Flushing of the Diesel Exhaust Fluid System” .
2. Inspect the DEF pump module for physical damage. Replace the DEF pump module if damage is found.
3. Inspect the DEF pump housing for signs of DEF leaks (1). Were DEF leaks found?
3.a Yes; carefully remove the frost protection membrane and turn it inside out to identify tears (2). Go to step
4.
3.b No; Go to step 5.
4. Were tears found in the frost protection membrane?
4.a Yes; replace the membrane and DEF pump filter kit only and reuse the DEF pump.
Note : This issue is known to cause Fault Code SPN 4374/FMI 0 – Under Pressurized Diesel Exhaust Fluid
System to be logged.
4.b No; replace the DEF pump.
5. If the DEF pump housing is not leaking, it can be reinstalled.
Installation of the Diesel Exhaust Fluid Pump Module
Note : If air pressure is greater than 620 kPa (90 psi), use a pressure regulator.
1. Using a rubber tipped air gun to seal around the DEF pump inlet fitting, apply clean regulated shop air to
the DEF pump inlet fitting (1) for three to five seconds.
2. Install the two bolts (5) that fasten the Diesel Exhaust Fluid (DEF) pump (1) to the mounting bracket (3).
Torque to 18 N·m (13 lb·ft).
3. Install the DEF pump and mounting bracket onto the mounting studs and install nuts (2) and washers.
Torque to 31 N·m (23 lb·ft).
4. Connect the DEF pump electrical harness connector.
NOTICE
To connect a DEF coolant line, push the line coupling onto the DEF port male connector,
then pull back gently on the coupling to engage the holding clip in the locked position.
5. Verify the DEF lines and connection fittings are clean; connect the DEF suction line and pressure line.
6. Connect the DEF return line to the DEF header.
7. Verify that the coolant lines and connectors are clean and then install the coolant lines to the pump.
8. Install the protective cover (1). Install and torque bolts to 50 N·m (37 lb·ft).
9. Fill the cooling system.
10. 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.
11. Using DiagnosticLink , perform an ADS Priming Function to prime the DEF system and check for leaks.
Flushing of the Diesel Exhaust Fluid System
NOTICE
If the Diesel Exhaust Fluid (DEF) system becomes contaminated with diesel fuel, the DEF
system will have to be flushed along with replacing the DEF Pump, Dosing Unit, and DEF
Tank Header Unit Screens.
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. Disconnect all the Diesel Exhaust Fluid (DEF) lines. Flush out all DEF lines with warm water. Use shop air
to blow out any remaining water and contamination from the lines. Refer to section “Removal of the Diesel Exhaust
Fluid Lines” .
4. Remove the DEF tank and flush it out with warm water.
Refer to section “Removal of the 13- and 23-Gallon Diesel Exhaust Fluid Tank” .
Refer to section “Removal of the Six-Gallon Diesel Exhaust Fluid Tank” .
5. Remove the DEF pump module. Refer to section “Removal of the Diesel Exhaust Fluid Pump Module” .
6. If not contaminated from diesel fuel, cover the DEF outlet port with a shop towel and use compressed air
and a rubber-tipped blow gun to force air through the inlet port side of the DEF pump.
7. Remove the DEF pump filter and inspect for contamination. Refer to section “Removal of the Diesel Exhaust Fluid
Pump Module Filter” . If contaminated, replace filter.
8. Remove the dosing unit. Refer to section “Removal of the Diesel Exhaust Fluid Dosing Unit” .
9. If not contaminated from diesel fuel, use compressed shop air and a rubber-tipped blow gun to force air
through the inlet of the DEF doser.
10. Connect the batteries. Refer to OEM procedures.
11. Check for any leaks.