[bobbecky]

The DPF system (diesel particulate filter) is what goes into REGEN. The DEF system continuously injects the fluid into the converter depending on the NOX sensors, one ahead of the converter and one after the converter, which tells the computer how much DEF fluid to inject to control the NOX level coming out of the exhaust. These are two separate systems. It is very possible the sensors are not working properly. We had one totally fail last year, and they replaced both of them, then had to calibrate them. It does seem like we are using less DEF now since that repair was done.