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Kevin, Technician
Category: Agriculture and Farm Equipment
Satisfied Customers: 732
Experience:  Over ten years of expirence in Ag Electronics and Hydraulics
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Have a major problem and a time crunch and getting no help

Customer Question

Have a major problem and a time crunch and getting no help ar all from the local dealer. On an 8335rt tractor. Says diesel exhaust fluid pressure low. And derates the tractor. I changed the pump out. Black box above the tank with a wiring harness on the bottom and 2 lines coming from the tank and one going out to the tractor. And it still does not work. Pump never does anything. Cant find a fuse that is related to it at all. Can you help please
Submitted: 1 year ago.
Category: Agriculture and Farm Equipment
Expert:  Kevin replied 1 year ago.

Hello, my name is ***** ***** I can help you with your question.

The DEF dosing unit is powered by the ECU controller itself so there is no specific fuse to check. More then likely there are other underling fault codes that are more specific to the actual cause of the problem. The ECU performs a self test on the dosing unit at startup that will set other codes. The other codes should be shown after hitting accept on the codes as they show up.

One problem that we have seen is that the sock on the bottom of the suction tube in the DEF tank will get coated with a scum if diesel fuel or water has gotten in the tank. In this case the pump just can't suck DEF through the plugged sock causing it to fail to pull def. A cheat to check for this problem is to apply light pressure to the suction fitting on the tank head. The light pressure will temporarily displace enough of the scum to allow it to suck DEF for a short time. If you can get the code to go away temporarily following this procedure then the tank will need to be removed and thoroughly cleaned along with the sock on the bottom of the tank head.

If you are getting additional fault codes let me know what they are and I can help you narrow down the source of the fault.

Please keep me post as I will gladly assist with further diagnostics as needed.


Expert:  Kevin replied 1 year ago.


I just wanted to follow up to see how you were coming with the DEF problem? Please let me know if there is anything I can do to assist you.