Case IH 19066 (DTC 1899) - ECU – Engine Control Unit (ECU): Upstream oxidation catalyst temperature sensor voltage is higher than expected.

The signal voltage from the temperature sensor located just before the Diesel Oxidation Catalyst (DOC) has exceeded the normal operating range, indicating an open circuit or a short to a high-voltage source within the sensor itself or the wiring harness.

• MAXXUM T4E
• 240 Series Axial-Flow Combines (7240, 8240, 9240)
• Farmall series (90C, 100C, 110C, 120C)
• Maxxum
• Puma
• Magnum series
• Case 570NXT Tier 4A Tractor Loaders

1. 1

   Visually inspect the wiring harness leading to the upstream oxidation catalyst temperature sensor for melted wires, chafing, or physical damage.

2. 2

   Disconnect the sensor and inspect the pins on both the sensor side and the harness side for corrosion, pushed-out pins, or moisture.

3. 3

   Check the signal wire for continuity back to the Engine ECU.

4. 4

   Test the signal wire for a short to voltage, which would trigger the 'voltage higher than expected' fault.

5. 5

   Verify that the ECU is providing the correct reference voltage (usually 5V) and a solid ground to the sensor circuit.

6. 6

   Measure the resistance across the sensor's terminals. If the multimeter reads 'OL' (open loop), the internal thermistor has failed.

1. 1

   Safety First

   Turn off the machine, remove the key, and disconnect the battery. Ensure the exhaust system has completely cooled down to prevent severe burns.

2. 2

   Locate the Sensor

   Find the upstream oxidation catalyst temperature sensor on the exhaust aftertreatment assembly. It will be threaded into the exhaust pipe upstream of the DOC canister.

3. 3

   Disconnect

   Unplug the electrical connector for the sensor.

4. 4

   Removal

   Apply penetrating oil to the threads of the sensor and let it sit (exhaust sensors are notorious for seizing due to extreme heat cycling). Carefully use a line wrench or specialized sensor socket to unthread the sensor from the exhaust pipe.

5. 5

   Installation

   Apply a small amount of high-temperature anti-seize compound to the threads of the new sensor (ensure none gets on the sensor probe itself). Thread the new sensor into the exhaust pipe and torque it to the OEM specification found in your specific machine's service manual.

6. 6

   Reconnect

   Plug the sensor's electrical connector back into the engine wiring harness. Ensure it clicks and locks securely.

7. 7

   Clear Codes

   Reconnect the battery. Turn the ignition on and use the Case IH Electronic Service Tool (EST) or a compatible diagnostic scanner to clear the inactive 19066 / 1899 fault code.

8. 8

   Verification

   Start the engine and monitor the live data for the upstream DOC temperature. Verify that the temperature reading is plausible and that the fault code does not return.