Case IH 19878 – Engine Control Unit (ECU) or Aftertreatment Control Module (ACM): DEF/AdBlue Pump Motor Pressure sensor Signal error for CAN message

The control module is not receiving a valid, plausible pressure reading from the DEF (Diesel Exhaust Fluid) pump motor pressure sensor via the CAN bus network. This can be caused by a physical failure of the pressure sensor inside the DEF pump, an internal pump leak, crystallized DEF fluid blocking the sensor, or an electrical/CAN bus communication dropout.

• Tier 4b
• Puma
• Maxxum
• Optum
• Steiger
• Magnum
• Axial-Flow 140 series
• Axial-Flow 240 series
• Axial-Flow 9230

1. 1

   Check battery and voltage with a load tester to rule out momentary voltage dips causing CAN bus dropouts

2. 2

   Inspect the electrical harness and connectors from the ECU/ACM to the DEF pump for road debris damage, water ingress, or corroded pins

3. 3

   Check the outside of the pump and DEF lines for white, crusty residue indicating DEF crystallization and internal blockages

4. 4

   Run a system pressure test using a diagnostic tool to verify if the system can build to approximately 6 bar (87 psi)

1. 1

   Clean the Area

   Thoroughly clean the area around the DEF tank and pump assembly using a suitable solvent or warm water to prevent dirt from entering the SCR system.

2. 2

   Disconnect Power and Lines

   Disconnect the negative battery cable. Disconnect the electrical connector, the DEF supply line, and the coolant heating lines (if equipped) from the DEF pump module.

3. 3

   Remove the Pump

   Depending on the machine's architecture, either unbolt the remote-mounted DEF doser pump from the frame rail or remove the flange assembly to pull the integrated pump header out of the DEF tank.

4. 4

   Install the New Pump

   Insert the replacement DEF pump assembly. Reconnect the fluid lines, coolant lines, and the electrical connector.

5. 5

   Saturate the Filter

   If the new pump fails to build pressure immediately, the internal filter may be dry. Allow the pump to sit in the DEF fluid for a period of time to re-saturate the filter.

6. 6

   Prime and Clear Codes

   Reconnect the battery. Use the Case IH Electronic Service Tool (EST) to clear the fault codes and run a DEF system leak test / prime cycle to pressurize the system and verify the CAN signal is restored.