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I have 2018 f-350 6.7 Powerstroke. The CEL just activated, code generated P20C2. I read up a bit about the issues that can trip this code and resulting severity. I scheduled a service to get it addressed but that is a month out.
My understanding is that the reductant heater is not activated until the reductant temperature sensor detects the DEF approaching a freezing temperature. So until the reductant temperature threashold is reached, the heater is not activated. The heater is not used until needed. Is this a valid understanding? Also, I believe there are three reductant heaters (tank,pressure,pump) on the 2018 f-350.
The CEL tripped at startup, after a brief shutdown (engine was at normal operating temperature at shutdown). When I scanned for the fault I got P20C2; no other DTCs present. The ambient temperature was about 70f; there is no risk of any DEF freeze out.
Also, the article I read specific to this code (P20C2) indicates if it trips during warm weather suspect a PCM programming error. .( https://www.obd-codes.com/p20c2 ). My vehicle is 100% stock.
I am just trying to get a better understanding of the issue and learn what other owners have experienced.
I think if it were me, I would clear the code and see if it comes back, because as you have already said, the heater shouldn't be on at the current ambient outside air temps.
I removed the plastic dirt cover (collector) on the bottom of the DEF tank. The connector (two wire) looked good, but I gave it a mild tug just to be sure. And....the CEL cleared during startup. So I don't know if this was the fix or if I had enough run cycles to clear the CEL.
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