21679299 | Genuine Volvo® ADblue Pump Assembly For FH, FM, FMX

 1. Store the fluid

• The vehicle carries AdBlue (DEF) in a separate tank
• This fluid is needed to clean exhaust gases

2. Pump activates when needed

• The AdBlue pump turns on based on engine load, temperature, and emissions levels
• It decides when and how much fluid is required

3. Pressurize the fluid

• The pump builds the correct pressure
• This ensures accurate delivery (not too much, not too little)

4. Deliver AdBlue to the injector

• The pump sends fluid through lines to a dosing injector in the exhaust

5. Enable the Selective Catalytic Reduction process

• AdBlue is sprayed into hot exhaust gases
• It turns into ammonia

6. Convert harmful gases

• The ammonia reacts with NOx (pollution)
• Converts it into:
  • nitrogen (harmless gas)
  • water vapor

7. Keep the vehicle compliant

• Ensures the engine meets emissions laws
• Prevents warnings, derates, or shutdowns

1. Warning message appears

• “Check emissions system”
• “Service DEF system”
• Check engine light comes on

2. Fault codes stored

• Codes related to SCR/DEF system
• Common ones involve:
  • low pressure
  • dosing faults
  • pump performance

3. Incorrect DEF usage

• DEF level doesn’t drop normally
• Or drops too fast

4. Poor dosing / emissions issues

• The system can’t properly run Selective Catalytic Reduction (SCR)
• Leads to higher NOx readings internally

5. Engine performance warning

• Reduced power message
• Engine may feel slightly weaker

6. Limp mode (derate)

• Speed and power limited
• Common on trucks:
  • 55 mph limit
  • torque reduction

7. No-start or shutdown (severe cases)

• After repeated faults:
  • countdown warnings
  • vehicle may refuse to restart