DD15 DEF Pressure Sensor

give me the fault code in spnxxx fmixx format and I will help you. usually DEF pressure sensor does not go bad. it's something else. That head ache I had twice on my truck.

 

complete troubleshooting for your issue ---> https://ddcsn-ddc.freightliner.com/cps/rde/xbcr/ddcsn/713-13.pdf

I think the problem comes from PLU(or aka PLV). That device is junk, gets bad every 200k miles . Located on rear top side of transmission. Made by Wabco and made in Poland. Here is it--> http://www.ebay.com/itm/Meritor-Wab...ash=item3f447807ca:g:WTQAAOSwkNZUqr14&vxp=mtr

also check out this document --> https://ddcsn-ddc.freightliner.com/cps/rde/xbcr/ddcsn/901-13.pdf

 

If a few pneumatic switching valves have been replaced and the problem has came back you probably have oil in the air system. Take the 1/4 air line off of the PLU on the side with a "T" fitting on it. If it has oil in it........ You need a lot of repairs. Air dryer maintenance is very important on EPA10 Freightliners.

 

if you put brand new compressor and new air dryer still you will have a little oil in PLV. And that little oil is the killer of PLV . Engineers of that plv are big brains. Instead of regular black rubber they could use a little expensive oil resistant Viton 75 rubber and all problems could be solved. Do you remember first generation VPODs? they all had short life and later the manufacturer changed rubber to Viton.