Case IH 19066 (F-4765-03) – Engine Control Module (ECM) or Dosing Control Unit (DCU) / Aftertreatment Control Module: Upstream oxidation catalyst temperature sensor voltage is higher than expected

The control module is receiving a voltage signal from the upstream Diesel Oxidation Catalyst (DOC) temperature sensor that exceeds the normal operating parameters. The FMI 03 designation typically points to a "Voltage Above Normal" condition, which is almost always caused by an open circuit, a disconnected sensor, or a short to a high-voltage source.

• VESTRUM CVX
• 240 Series Axial-Flow Combines (7240, 8240, 9240)
• 130/140/150/230/250 series Combines (5130, 7140, 9250)
• Farmall series (40-50, 100C, 105A, 115U)
• Maxxum (120-150)
• Puma (130-240)
• Steiger (350-620)
• Quadtrac / Rowtrac

1. 1

   Visual Inspection: Inspect the wiring harness leading to the upstream DOC temperature sensor. Look for melted insulation, chafing against the exhaust, or broken wires.

2. 2

   Connector Check: Disconnect the sensor and inspect the pins on both the sensor side and the harness side. Look for corrosion, moisture ingress, or pushed-back pins.

3. 3

   Voltage/Continuity Test: With the key ON (engine OFF), check the harness side for proper reference voltage and ground. Test the signal wire for a short to battery voltage (which triggers the "voltage higher than expected" code).

4. 4

   Sensor Resistance Test: Measure the resistance across the sensor's pins. If the sensor reads as an open circuit (infinite resistance), the sensor itself has failed internally and must be replaced.

1. 1

   Safety First

   Turn off the engine, remove the key, and disconnect the battery. Allow the exhaust system to cool completely, as the DOC assembly operates at extremely high temperatures.

2. 2

   Locate the Sensor

   Locate the upstream oxidation catalyst temperature sensor. It is threaded into the exhaust pipe just before the Diesel Oxidation Catalyst (DOC) canister.

3. 3

   Disconnect

   Unplug the electrical connector from the sensor harness.

4. 4

   Removal

   Using a suitable wrench or specialized sensor socket, carefully unscrew the sensor from the exhaust housing. Note: Exhaust sensors frequently seize; applying penetrating oil and allowing it to soak may prevent thread damage.

5. 5

   Preparation

   Apply a small amount of 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 itself.

6. 6

   Installation

   Thread the new sensor into the exhaust housing by hand to prevent cross-threading, then tighten to the OEM torque specification.

7. 7

   Reconnect

   Plug the sensor's electrical connector back into the machine's harness. Ensure the wire is routed and secured away from direct contact with the hot exhaust piping.

8. 8

   Clear Codes

   Reconnect the battery. Use the Case IH Electronic Service Tool (EST) or a compatible heavy-duty scanner to clear the inactive 19066 fault code.

9. 9

   Validation

   Start the engine and monitor the exhaust temperature parameters on the diagnostic tool or cab display to ensure the sensor is reading correctly and the code does not return.