Case IH F-3242-31 - ECU – Engine Control Unit (ECU): Upstream SCR temperature sensor comparison to a calculated temperature value failure

The engine control system uses a mathematical model to calculate what the exhaust temperature should be as it enters the Selective Catalytic Reduction (SCR) catalyst, based on current engine load, speed, and ambient conditions. If the physical Upstream SCR Temperature Sensor reports a value that deviates significantly from this calculated model, the system flags the sensor data as implausible, which typically triggers an engine derate to protect the emissions system.

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1. 1

   Check system grounds (Known Service Issue): Verify, clean, and tighten the main cab ground straps and ECU grounds. Poor connections in the cab/roof harness can cause erratic voltage drops that directly trigger this code.

2. 2

   Perform a cold soak temperature comparison: After the machine has been sitting overnight, use a scan tool to compare the Upstream SCR Temperature Sensor reading to the Downstream SCR Temperature Sensor and Ambient Air Temperature sensor. All three should read within a few degrees of each other.

3. 3

   Inspect the wiring harness leading to the upstream SCR temperature sensor for chafing, melted insulation from exhaust heat, or corrosion inside the connector pins.

1. 1

   Power Down

   Turn off the machine and disconnect the negative battery cable to prevent electrical shorts.

2. 2

   Locate the Sensor

   Locate the Upstream SCR Temperature Sensor. It is threaded into the exhaust pipe assembly before the SCR catalyst canister.

3. 3

   Remove the Sensor

   Disconnect the electrical pigtail connector. Use a specialized sensor socket or line wrench to remove the sensor from the exhaust pipe. (Note: Exhaust sensors are prone to seizing; apply penetrating oil and allow it to soak if the sensor is stuck).

4. 4

   Prepare the New Sensor

   Apply a small amount of high-temperature anti-seize compound to the threads of the new sensor. Do not get any anti-seize on the sensor probe tip, as this will contaminate it.

5. 5

   Installation

   Thread the new sensor into the exhaust pipe and tighten it to the OEM torque specification.

6. 6

   Reconnect

   Plug in the electrical connector and reconnect the battery.

7. 7

   Clear Codes and Test

   Connect a diagnostic scan tool, clear the F-3242-31 / 19041 fault code, and perform a forced stationary regeneration or a test drive under load to verify that the exhaust temperature readings match the calculated values and the code does not return.