Ambient air and DEF problems and solution

[trdodd07]

(08-21-2016 )Rawze Wrote:  .
Wow! -- That is a nice article and you have pictures and part numbers too. Thank you for taking the time to do this for everyone here on the forum. I am sure it will help others.

Just doing what I can to hopefully make it easier for the next person with similar problems.

I did forget to mention, in Insite on the Features and Parameters list, OEM ambient air temperature sensor can be enabled/disabled. So, there is a possibility that some trucks may not have that sensor, or, you may try to disable it, though I think the DEF system relies on it's reading to operate.

I think the DEF system cross checks the tank temp with the ambient air temp, and if there is a large difference (54*F according to quickserve), then it will set the 1679 fault. With that, it thinks that there is an internal error with the DEF controller or dosing unit, and then disables the system.