Case IH F-3234-06 - ECU – Engine Control Module (ECM / Engine ECU) / Dosing Control Unit (DCU) / Aftertreatment Control Module (ACM): Downstream NOx sensor internal failure (Short Circuit Error)

The control module detects a short circuit in the sensor's internal heater circuit or measurement cell, or the sensor reports an internal short circuit via the CAN bus.

• MAGNUM AFS Connect
• Case IH Magnum 235 – 340 (Series 4)
• Case IH Steiger Series
• Case IH 240 Series Axial-Flow Combines
• Case IH Farmall Series (with SCR)

1. 1

   Inspect the wiring harness leading to the downstream NOx sensor (located on the exhaust tailpipe after the DOC/SCR assembly) for melted insulation, chafing against the chassis, or exposed wires.

2. 2

   Disconnect the sensor and inspect the pins for corrosion, moisture, or bent terminals.

3. 3

   Use a multimeter to check the sensor's power supply voltage and verify the CAN bus communication lines. Check for continuity to ground on the harness side to rule out a wiring short.

4. 4

   Check the emissions/aftertreatment fuse block for any blown fuses caused by the shorted heater circuit.

1. 1

   Power down machine

   Turn off the machine and disconnect the battery to prevent electrical spikes.

2. 2

   Locate sensor

   Locate the downstream NOx sensor on the exhaust pipe, directly after the Selective Catalytic Reduction (SCR) canister.

3. 3

   Disconnect sensor

   Unplug the electrical connector for the downstream NOx sensor.

4. 4

   Remove sensor

   Using a specialized NOx sensor socket or a 22mm wrench, carefully unscrew the sensor from the exhaust bung. Penetrating oil may be required if seized due to high exhaust heat.

5. 5

   Prepare new sensor

   Apply a high-temperature anti-seize compound to the threads of the new sensor (if it does not come pre-applied from the factory). Do not get anti-seize on the sensor probe tip.

6. 6

   Install new sensor

   Thread the new sensor into the exhaust bung by hand to prevent cross-threading, then torque to the manufacturer's specification.

7. 7

   Reconnect wiring

   Route the wiring harness away from extreme heat sources and plug in the electrical connector.

8. 8

   Clear codes and test

   Reconnect the battery. Use the Case IH Electronic Service Tool (EST) to clear the F-3234-06 fault code. Perform an aftertreatment system test or a manual stationary regeneration to verify the sensor is reading correctly and the code does not return.