Received message that service DEF take to shop. Code P207F came up. Researched code and cannot understand what it is or the severity. Could someone help me understand this thing and what I can do to correct the problem.

 

This code refers to the quality of the DEF. Possible causes include contaminated DEF or a fault with the system wiring.

There’s a DEF quality sensor mounted on the tank. At key on its powered by fuse #61 and SCR Relay #2.

Start by confirming the relay and fuse are good. If so then verify battery voltage at the sensor with the key on (it might only be powered on for a couple of seconds until the engine is started so having a helper to cycle the key may be useful).

If you think the DEF could be contaminated, testers are available off the shelf or you could drain the tank and fill with new DEF.

Diagnosis can go several directions depending on what you find with each test.

 

Thank you. I will check this out.

 

Also the message went out while wife driving. She called me a few minutes ago. I have not cleared the code that came up yesterday. Should I clear the code and see what happens. Will still check the items you mentioned.

 

Clearing the code won’t hurt anything but it’s not necessary either.

For the message to clear on its own means the fault is intermittent or other temporary factors that affect DEF quality caused the message to set - frozen DEF or crystallized DEF deposits on the injector nozzle are a couple of examples.

If it’s an intermittent fault, the best first step is thorough inspection of the undercarriage wiring harness, connector terminals and exhaust. Look for chafed and damaged areas of the harness, loose or corroded connectors, and exhaust leaks. Clean connectors with compressed air and a small amount of electrical contact cleaner.

I’m not completely familiar with Cummins’ SCR system but other automotive systems also compare the upstream and downstream NOx readings to determine system efficiency - when the downstream NOx reaches a calibrated or calculated threshold, the DEF quality message can set. Given OBD2 standards on light duty and passenger vehicles, it’s likely Cummins has a similar protocol/derate mode as well.

 

Thank you. When she got home I checked and the message had cleared and scanned codes and the code was gone also. I did not do any clearing of codes.

 

It may have clear itself after doing a regeneration when driving.