ASP5410-6506711 | Genuine International® Diesel Exhaust Fluid DEF Sensor Head

Electrical Connector: Delphi Metri-Pack 15 5-Pin (Jumper Harness)
Sensor Type: Analog
DEF Header Height (IN): 11
DEF Suction Fitting Dia. (IN): 3/8 SAE J2044
DEF Return Fitting Dia. (IN): 5/16 SAE J2044
Coolant Inlet Fitting Dia. (IN): 5/8 Hose Bead
Coolant Outlet Fitting Dia. (IN): 5/8 Hose Bead
In-Tank Filter: 40µ
Tank Interface: 4.05 Dia. Bore Seal

• Measure DEF level in the tank

• Monitor DEF temperature

• Check DEF quality/concentration

• Detect system faults or contamination

• Control proper DEF dosing for the SCR system

• Ensure emissions compliance and prevent engine restrictions

1. Warning Lights and Fault Codes

• “Check Engine” light or “DEF system fault” message on the dash.

• SCR or emissions-related fault codes (often starting with P20xx, such as P203F, P205B, P206A, P207F).

• DEF quality sensor errors or temperature sensor circuit faults stored in the ECM.

• “Service DEF system” or “Vehicle will derate in XXX miles” messages.

2. Incorrect DEF Level Reading

• DEF gauge shows empty or full all the time, regardless of actual level.

• Gauge fluctuates or drops suddenly after refilling the DEF tank.
  Cause: DEF level sensor inside the header is malfunctioning or covered in crystallized DEF.

3. DEF Freezing or Not Thawing

• In cold weather, the system takes too long to thaw or never thaws at all.

• The engine may derate because frozen DEF can’t be injected.
  Cause: The heater element in the DEF header has failed.

4. DEF Quality or Concentration Errors

• ECU reports poor DEF quality or incorrect urea concentration even when fresh DEF is used.
  Cause: The quality sensor inside the header is faulty or contaminated with crystallized DEF.

5. Engine Derate or Power Limitation

• The truck goes into limp mode or reduces speed (e.g., limited to 5 mph) after warnings are ignored.
  Cause: The ECM forces derate to prevent emissions violations if it detects the SCR system isn’t working properly.

6. Crystallization or Contamination

• Visible white crystals or buildup around the DEF tank or header connector.

• Poor electrical contact due to corrosion or DEF leakage.
  Cause: DEF exposure to air causes crystallization, which can damage sensors or block passages.