2016 Mack Pinnacle - P208E Fault - DEF Dosing Valve Clogged

Question

Keep getting P208E 'Reductant Injection Valve Stuck Closed'. The truck hasn't used any DEF in the last 500 miles and I'm worried about an SCR derate coming on. I can hear the DEF pump priming but it sounds like it's laboring.

I pulled the injector out of the exhaust pipe and it looks like it's covered in white crystallized DEF. I tried cleaning it with hot water but the code persists. The pump pressure seems to hit 130psi then drops.

BackyardBilly · Accepted Answer

✅ Confirmed fix: The DEF injector nozzle was internally seized. Even after cleaning the outside, the solenoid wouldn't cycle. Replaced the dosing valve (Part # 22391563) and ran a 'SCR Crystal Sublimation' service routine. DEF flow returned to normal and codes cleared.

TacomaTess · Answer

You need to check the heating element in the DEF line. If the line is frozen or the heater is dead, the pump can't push the fluid through. But if you're in warm weather, that's not it.

2016 Mack Pinnacle - P208E Fault - DEF Dosing Valve Clogged

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