Case IH 19066 – ECU: Upstream oxidation catalyst temperature sensor voltage is higher than expected.

This code indicates that the signal voltage returning from the upstream Diesel Oxidation Catalyst (DOC) temperature sensor is exceeding the normal operating range. This almost always points to an open circuit, a disconnected sensor, a broken wire, or a short to a higher voltage source.

• Tier 4b
• 240 Series Axial-Flow Combines (7240, 8240, 9240)
• Farmall series (40, 45, 50 CVT)
• Magnum
• Maxxum
• Steiger series
• Case STM N Series Loaders
• Excavators

1. 1

   Visually inspect the upstream DOC temperature sensor and its wiring harness for heat damage, melting, or vibration chafing.

2. 2

   Disconnect the sensor and inspect the connector pins for corrosion, moisture, or pins that have pushed back into the connector housing.

3. 3

   Perform a resistance test using a multimeter to measure the resistance across the sensor's pins. If the multimeter reads 'OL' (infinite resistance) or an extremely high value, the sensor has failed internally (open circuit) and must be replaced.

4. 4

   Perform a harness test by turning the key ON (engine off) and measuring the voltage at the harness-side connector. Check for the presence of reference voltage, a good ground circuit, and ensure the signal wire is not shorted to power.

1. 1

   Ensure safety

   Ensure the machine is turned off, the key is removed, and the exhaust system has completely cooled down to prevent severe burns.

2. 2

   Locate sensor

   Locate the upstream oxidation catalyst temperature sensor. It will be threaded into the exhaust piping just before the Diesel Oxidation Catalyst (DOC) housing.

3. 3

   Disconnect sensor

   Unplug the electrical connector from the sensor harness.

4. 4

   Remove sensor

   Apply penetrating oil to the base of the sensor threads and let it sit for a few minutes. Use a specialized sensor socket or a line wrench to carefully unthread the sensor from the exhaust pipe.

5. 5

   Prepare new sensor

   If the new sensor does not come with pre-applied anti-seize, apply a very small amount of high-temp anti-seize compound to the threads. Caution: Do not get any compound on the sensor probe itself, as this will ruin the sensor.

6. 6

   Install new sensor

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

7. 7

   Reconnect harness

   Plug the electrical connector back in, ensuring the locking tab clicks into place. Secure any loose wiring away from direct heat sources.

8. 8

   Clear codes

   Connect a diagnostic tool (such as the Case IH Electronic Service Tool / EST or an aftermarket equivalent like Jaltest) to clear the 19066 fault code from the ECU.

9. 9

   Verify repair

   Start the engine and monitor the live exhaust temperature data to ensure the sensor is reading correctly and the code does not return.