P20F4

Symptoms

• Check Engine light comes on
• Reduced engine power
• Increased fuel consumption
• Low AdBlue level message (even with a full tank)
• The engine may go into emergency mode

Causes

• Low AdBlue level in tank
• Reagent pump malfunction
• SCR injector clogged
• Problems with NOx sensors
• Open circuit or wiring fault

How to Fix

1. Check AdBlue level and top up if necessary
2. Diagnose the reagent supply pump
3. Check and, if necessary, clean or replace the SCR injector
4. Scan the system for other fault codes
5. Check the condition of wiring and connections to SCR system components

Related codes

Error P20F4 by Vehicle Brand