2020 Volvo VNL 760 - D13 Engine - SPN 5246 FMI 0 (SCR Induction)

Question

My 2020 VNL is threatening a 5 MPH derate. The dash says 'Efficiency Low'. I replaced the DEF doser valve thinking it was clogged, but the code came back after the first trip. The DEF pump pressure seems okay (around 130 psi), but I'm seeing white smoke from the exhaust during what feels like an attempted regen.

I'm worried about the SCR catalyst being crystallized. I ran a DEF crystalization test via Tech Tool and it failed. I'm looking for the next step before I spend $6k on a new SCR brick.

MackMarty · Accepted Answer

✅ Confirmed fix: Found the DEF line heater had failed, causing the DEF to stay too cold and not atomize correctly, leading to massive crystallization on the decomposition pipe. Replaced the line and the 'seventh' injector pipe (mixing pipe). Cleaned the crystallized DEF out of the pipe manually. System is now converted correctly.

FleetOwnerFiona · Answer

Check your DEF quality first. Get a refractometer and make sure it's 32.5%. If the fluid is old or contaminated, it will cause low conversion efficiency. Also, check the NOx sensors to see if the outlet sensor is biased high.

2020 Volvo VNL 760 - D13 Engine - SPN 5246 FMI 0 (SCR Induction)

Suggest a repair