Cummins ISX DEF Doser

The Cummins ISX DEF doser is an important part of your trucks after treatment system and when functioning properly helps to reduce emissions. When it is faulty, it can cause a variety of issues from excessive DEF build up to check engine lights and engine derate. It is simple and straightforward to replace however it is common to break the mounting bolts which would require extracting the broken bolt or replacing the pipe its mounted to. For Cummins specific How to guides, visit our Cummins page.

DEF Doser Location:

The DEF doser found on the ISX15 is mounted on the pipe connecting the DPF to the SCR visible behind the DPF. No DPF heat shields need to be removed to access it, it is facing the driveshaft.

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Cummins ISX DEF Doser Replacement Procedure:

• Make sure engine is off with the ignition in the OFF position
• Locate the DEF doser
• Crimp off both coolant lines going to the doser using crimp off pliers
• Remove wire connector from doser by pushing in the tab and pulling the connector out
• Cut zip tie holding DEF line to bracket in front of the doser
• Remove DEF line from the doser by squeezing the plastic clip and pulling the fitting off of the nipple
• Remove both coolant lines from the doser by squeezing the sides of the fitting together and pulling the fitting away from the nipple
• Remove the DEF doser mounting bolts using a 10mm socket, extension and ratchet
• Remove DEF doser
• Install new DEF doser to pipe by reinstalling and tightening the 10mm bolts
• Reinstall coolant and DEF lines to doser
• Ziptie DEF line to bracket as it was before
• Reinstall wire connector to doser
• Remove both coolant crimp off pliers
• Turn key on and check for any coolant leaks, faults or any other issues