4254201C91 | Genuine International 9.5 Gal Def Sensor

Compatible Vehicles & Engines

Part number is engineered as an OEM replacement for International / Navistar medium- and heavy-duty trucks equipped with medium-to-large 9.5-gallon DEF tanks:

• Class 8 Highway Trucks: International ProStar, LT Series, LoneStar, RH Series.

• Vocational & Regional Trucks: International WorkStar, DuraStar, HV Series, HX Series, MV Series.

• Buses & Chassis: IC Bus platforms equipped with SCR emissions systems.

• Compatible Engine Platforms: Cummins ISX15 / X15, Cummins L9 / B6.7, and Navistar N13 / A26 engines.

1. What is it?

Part serves as the combined fluid suction unit, electronic quality/level sensor stem, and anti-freeze heating assembly for medium-to-heavy commercial trucks. It monitors fluid conditions in real time to keep emissions levels fully compliant with EPA regulations.

2. Integrated Functions & Key Features

• Quality, Level & Temperature Sensing (QLS): Employs integrated digital sensors to measure DEF level, check urea concentration (ensuring 32.5% purity and preventing dilution), and monitor fluid temperature over the CAN bus network.

• Fluid Suction & Return Tubes: Heavy-duty stainless steel pickup lines deliver DEF to the dosing pump and return excess fluid safely back to the 9.5-gallon tank.

• Coolant Heating Coil: Features an internal tube loop connected to the engine's coolant circuit to thaw frozen DEF (which solidifies at 12°F / -11°C) during winter operation.

• In-Tank Filtration: Equipped with a bottom mesh filter screen that blocks dirt and particles from entering the dosing pump.

1. Active Check Engine Light (CEL) & SCR Fault Codes

The Engine Control Module (ECM) detects corrupted or missing CAN-bus signals from the integrated Quality, Level, and Temperature Sensor (QLS):

• Common Diagnostic Trouble Codes (DTCs):

  • SPN 1761 / FMI 9, 11, 19 (DEF Tank Level - Communication Error or Incorrect Signal)

  • SPN 3364 / FMI 2, 9, 11 (DEF Quality - Abnormal Concentration / Non-DEF Detected)

  • SPN 3031 / FMI 9, 11 (DEF Tank Temperature - Out of Range / Erratic Data)

  • SPN 4364 / FMI 18 (SCR NOx Conversion Efficiency Below Limit)

2. Incorrect DEF Level Gauge Readings

• Symptom: The dashboard gauge displays "Empty" when the 9.5-gallon tank is completely full, freezes at a specific percentage, or bounces erratically between empty and full while driving.

• Cause: Internal float/ultrasonic sensor degradation or fluid ingress into the internal electronics.

3. Engine De-rate & Speed Reductions

• Symptom: A "Poor DEF Quality" warning appears on the driver display, followed by a timer warning for imminent speed de-rate (e.g., restricted to 55 mph, then 5 mph).

• Cause: Sensor calibration drift sending incorrect concentration readings to the ECM—even when filled with pure, fresh ISO 22241 DEF.

4. DEF Tank Heating & Freezing Faults

• Symptom: In cold weather, the system logs low-pressure codes (SPN 3556) or tank thaw timeouts because fluid remains frozen inside the tank.

• Cause: Clogged internal coolant heating coils or a failed temperature sensor misreporting the tank fluid temperature.