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2011 6.7L F350 P207F DEF SCR
Truck threw this code a few weeks ago with ~110,000 miles. Speed limited to 55miles in 200 miles starts counting down. No other codes. Siphoned out DEF tank and refilled. It only took about 4 gals so I figured it didn't all get out. Cleared the codes via Forscan. Truck went about a week code reappeared, counting down 37 miles to speed limited....
Purchased Nox sensor and replaced. Reset code, drove it around until NOx_AFT_EVAL=yes, at which point it went to Speed Limited to 55mph on restart.
Dropped the DEF tank, dumped it all out to confirm empty and refilled with 2.5 gal of new BlueDEF. Removed DEF Injector and visually inspected, confirmed it opens and flows via bench 5v power supply and compressed air.
Drove truck again until NOx_AFT_EVAL=yes and right on que - Speed Limited to 55mph on restart.
In running forscan in scope mode I am noting the following. Once the DEF pump activates, pressure remains constant around 73psi and pump duty cycle (no injection) is around 15%. Once the exhaust heats up it starts opening the injector. The injection is not constant, spurts of maybe 5% to 40% DC every couple seconds, then will go quiet for a few secs. Output looks like a little mountain range. NOX levels seem to react
Does anyone know the expected behavior of the DEF injector?
NOx levels are around 100-450ppm but will climb to 900 on hard accel and then the DEF injector seems to respond and they come back down.
Other than throwing more parts at it, sending it to the dealer, any thoughts? I do not think there is any more diagnosing I can do with ForScan?
Truck is stock as far as I can tell. Prior owner records show all service work done at Ford dealers in IL and FL, seems they hauled a camper back and forth seasonally.