Theory Of Operation

WARNING: This page is about a different variant/trim than selected.

When the Diesel Exhaust Fluid (DEF) system is in pressure control mode, the Powertrain Control Module (PCM) activates the DEF Supply Pump to refill the lines. As the lines fill, the pressure builds to the set point. When the pressure reaches the set point, the PCM turns on the DEF Injector to bleed air out of the Pressure Line. Each time the injector is turned off, the PCM monitors the amount of time it takes for the pressure to rise back to the set point to determine when all of the air is bled out of the line. The PCM will illuminate the MIL light immediately after the diagnostics runs and fails and diesel exhaust fluid injection into the aftertreatment system is disabled.

The PCM also monitors the DEF pressure buildup system to provide correct (overall) performance. If excessive air is detected during pressure buildup, the Purge Pump system draws fluid back into the DEF tank to remove the air. Once the purge is complete the pressure buildup is reinitialized.