Case IH 19274 – Engine Control Module (ECM) / Electronic Diesel Control (EDC): CAN timeout error - A1SCREGT (SCR catalyst upstream and downstream catalyst temperatures) message

The engine's control system has lost Controller Area Network (CAN) bus communication with the sensor module responsible for broadcasting the exhaust gas temperatures entering (upstream) and exiting (downstream) the Selective Catalytic Reduction (SCR) chamber. Without this data, the system cannot accurately calculate diesel exhaust fluid (DEF) dosing or monitor SCR efficiency.

• Tier 4b
• Case IH Puma
• Case IH Magnum
• Case IH Farmall
• 621F
• 921G

1. 1

   Check the CAN bus wiring harness between the ECM and the SCR temperature sensors for physical damage, chafing, or melted wires near the hot exhaust components

2. 2

   Inspect the connectors at the SCR temperature sensor module and the ECM for loose pins, moisture intrusion, or corrosion

3. 3

   Verify that the closed-tip sensors are receiving their required 5-volt supply (Pin 1) and have a solid common ground to the ECU (Pin 2)

4. 4

   Check for other active CAN timeout codes (such as U113F, U114A, or U114B) which might indicate a broader CAN bus failure rather than an isolated sensor issue

1. 1

   Power down the machine, turn off the battery disconnect switch, and allow the exhaust aftertreatment system to cool completely.

2. 2

   Locate the SCR catalyst temperature sensors on the exhaust aftertreatment assembly (typically mounted near the DOC and SCR chambers).

3. 3

   Disconnect the sensor module's electrical connector. Clean the contacts with an approved electrical contact cleaner and inspect for pushed-out pins.

4. 4

   Trace the wiring harness back to the ECM. Repair any broken, corroded, or shorted wires found during the visual inspection.

5. 5

   If the wiring, power, and ground are all verified as good, the internal CAN broadcasting circuitry of the sensor module has likely failed. Remove the faulty SCR temperature sensor assembly from the exhaust pipe.

6. 6

   Apply high-temperature anti-seize compound to the threads of the new sensor (if not pre-applied) and install it into the exhaust housing.

7. 7

   Reconnect the electrical harness, restore battery power, and use a diagnostic service tool (like CNH EST) to clear the fault codes.

8. 8

   Run the engine through a warm-up cycle to verify the ECM is receiving the A1SCREGT message and that the fault code does not return.