Case IH 19144 (DTC 9AEA) - ECU – Engine Control Unit (ECU) or Dosing Control Unit (DCU): CAN timeout error from DEF/AdBlue quality sensor

The control module has lost communication with the DEF (Diesel Exhaust Fluid) quality sensor over the CAN bus network. The sensor is failing to broadcast its data packets within the expected timeframe. This is an electrical or communication failure, historically known to be caused by ammonia gas permeating the sensor housing and corroding the internal circuit board.

• MAXXUM T4E
• 240 Series Axial-Flow (7240, 8240, 9240)
• Magnum Series (235, 250, 280, 310, 340, 380)
• Steiger Series
• Puma
• Maxxum
• Farmall

1. 1

   Inspect the CAN bus wiring harness connecting the DEF quality sensor to the ECU/DCU for disconnected cables, chafing, or broken wires

2. 2

   Disconnect the DEF quality sensor and inspect the connector pins for corrosion, moisture, or bent terminals

3. 3

   Verify power and ground to ensure the sensor is receiving the correct operating voltage and has a solid ground connection

4. 4

   Test CAN bus integrity by measuring the resistance across the CAN High and CAN Low pins (should read approximately 60 ohms) and check for short circuits to power or ground

5. 5

   Check for available software updates, as manufacturers have released updates that bypass the DEF quality sensor requirement

1. 1

   Preparation

   Turn off the machine, remove the key, and disconnect the battery to prevent electrical shorts.

2. 2

   Locate the Sensor

   Locate the DEF tank. The DEF quality sensor is part of the DEF header unit mounted at the very top of the tank.

3. 3

   Disconnect Lines

   Carefully disconnect the electrical harness connector from the DEF header. If applicable, disconnect the DEF fluid suction and return lines (be prepared to catch minor fluid spills).

4. 4

   Remove the Header

   Clean the area around the header to prevent dirt from falling into the DEF tank. Unscrew the locking ring or remove the mounting bolts securing the DEF header to the tank.

5. 5

   Extract and Replace

   Carefully lift the old DEF header assembly out of the tank. Insert the new DEF header/quality sensor assembly, ensuring the sealing gasket is properly seated.

6. 6

   Reassembly

   Tighten the locking ring/bolts to OEM torque specs. Reconnect the fluid lines and the electrical harness.

7. 7

   Clear Codes

   Reconnect the battery. Use a dealer-level diagnostic tool (such as the Case IH EST or Jaltest) to clear the inactive 19144 fault code and reset the SCR system parameters.

8. 8

   Test

   Start the engine and monitor the system to ensure the code does not return and the machine exits any derate conditions.