P208B Possible Causes
- Faulty reductant pump
- Reductant pump harness is open or shorted
- Reductant pump electrical circuit poor electrical connection
What Does It Mean?
How to Fix Code P208B
Check the “possible causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.
P208B Possible Symptoms
Illuminated engine light (or service engine soon warning light)
P208B Meaning
The reductant pump assembly contains a diaphragm pressure pump, pressure sensor, purge valve, outlet filter, and internal heating element. The reductant pressure sensor provides feedback to the Powertrain Control Module (PCM), which regulates system pressure by controlling pump speed using pulse width modulation. When the PCM requests reductant injection, the reductant injector opens and the pump operates, filling the reductant pressure line and injector while purging air from the system. Once all air is purged, the injector closes and the pump increases pressure to 73 psi (500 kPa). The system is then primed and the injector supplies DEF to the SCR catalyst as determined by the PCM.
When the vehicle is shut down, the PCM closes the injector and activates the reductant purge valve, causing the pump to reverse flow and purge pressure from the reductant pressure line. The PCM then opens the injector to allow gas into the reductant pressure line, enabling the pump to purge any remaining DEF from the system and return it to the reductant tank. The PCM closes the injector and returns the purge valve to its forward position. The PCM commands the glow plug control module to provide voltage to the reductant pump assembly’s internal heating element when reductant temperature approaches 12°F (-11°C)….