Case IH 19402 (DTC 9AAA) - ECU – Engine Control Unit (ECU) / SCR Controller: CAN timeout error - Urea tank level

Communication failure on the Controller Area Network (CAN) bus. The control module has stopped receiving the expected data frames (timeout) from the Diesel Exhaust Fluid (DEF) / Urea tank level sensor, which will eventually lead to an engine derate or power loss.

• MAXXUM T4E
• 240 Series Axial-Flow Combines
• 7240
• 8240
• 9240
• Magnum tractors
• Steiger tractors

1. 1

   Wiring Inspection: Check the wiring harness between the DEF/Urea tank level sensor and the ECU for physical damage, breaks, or short circuits.

2. 2

   Voltage Supply: Verify that the DEF tank level sensor controller is receiving proper operating voltage and has a solid ground.

3. 3

   CAN Bus Integrity: Test the CAN bus wiring (CAN High and CAN Low) at the sensor connector for proper resistance and continuity.

4. 4

   Network Interference: Check for CAN bus overload or interference. A fault elsewhere in the network could be causing error frames that disrupt the DEF sensor's communication.

1. 1

   Turn off machine and disconnect battery

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

2. 2

   Disconnect DEF sender unit

   Locate the DEF/Urea tank and disconnect the electrical connector at the DEF sender unit (header unit).

3. 3

   Inspect connector pins

   Inspect the connector pins on both the harness and the sensor side for corrosion, pushed-out pins, or moisture intrusion. Clean and repair as necessary.

4. 4

   Perform continuity and voltage tests

   Using a multimeter, perform continuity and voltage tests on the harness side of the connector to rule out a broken wire or short circuit between the tank and the ECU.

5. 5

   Repair wiring

   Repair any damaged wiring in the CAN bus or power supply circuits.

6. 6

   Diagnose DEF sender unit failure

   If the wiring harness, voltage supply, and CAN bus integrity are confirmed to be good, the internal CAN controller inside the DEF sender unit has failed.

7. 7

   Remove defective DEF sender unit

   Remove the defective DEF sender unit from the top of the DEF tank.

8. 8

   Install new DEF sender unit

   Install a new DEF sender unit, reconnect the electrical harness, and reconnect the battery.

9. 9

   Clear fault codes and verify

   Use a diagnostic service tool to clear the fault codes. Run the engine to verify the DEF level is reading correctly on the display and that the code does not return.