Case IH 19040 – Engine Control Module (ECM): Upstream Oxidation Catalyst Temperature Sensor Comparison to a Calculated Temperature Value Failure

This fault code indicates a plausibility error within the emissions system. The Engine Control Module (ECM) continuously calculates an expected (theoretical) exhaust temperature based on current engine operating conditions (load, speed, fueling, etc.). It then compares this calculated value to the actual physical reading provided by the Upstream Oxidation Catalyst (DOC) Temperature Sensor. If the actual sensor reading deviates significantly from the ECM's calculated value for a set period, the system logs fault code 19040. This usually points to a failing sensor, a wiring issue, or an exhaust leak altering the actual temperature.

• Tier 4b
• Case IH 240 Series Axial-Flow Combines
• Case IH Farmall 40, 45, and 50 Tractors (with Cab and CVT Transmission)
• Other Case IH / New Holland machinery utilizing the FPT Tier 4 Final / Stage V DOC and SCR aftertreatment systems

1. 1

   Visual Inspection: Inspect the wiring harness and connector leading to the upstream DOC temperature sensor. Look for melted wires, chafing against the exhaust, or corrosion inside the connector pins.

2. 2

   Exhaust Leak Check: Inspect the exhaust piping between the turbocharger and the Diesel Oxidation Catalyst (DOC). An exhaust leak can cause the actual exhaust temperature to drop, triggering the plausibility failure even if the sensor is perfectly fine.

3. 3

   Sensor Inspection: Remove the sensor and check the probe for excessive soot buildup or physical damage, which can insulate the sensor and cause sluggish or inaccurate readings.

4. 4

   Electrical Testing: Use a multimeter to check the sensor's resistance. Compare the reading against OEM specifications for the current ambient temperature to determine if the internal thermistor is out of range.

1. 1

   Cool Down

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

2. 2

   Disconnect Power

   Disconnect the negative battery cable.

3. 3

   Locate the Sensor

   Locate the Upstream Oxidation Catalyst Temperature Sensor. It is threaded into the exhaust pipe directly before the DOC canister.

4. 4

   Disconnect Wiring

   Unplug the electrical connector for the sensor.

5. 5

   Remove the Sensor

   Apply penetrating oil to the threads of the sensor and allow it to soak (exhaust sensors are prone to seizing). Carefully remove the sensor using a suitable wrench or specialized sensor socket.

6. 6

   Install the New Sensor

   Apply a small amount of high-temperature anti-seize to the threads of the new sensor (if it does not come pre-coated). Thread it into the exhaust pipe and tighten to the OEM torque specification.

7. 7

   Reconnect

   Plug the electrical connector back in, ensuring the wiring is routed safely away from direct contact with the hot exhaust piping.

8. 8

   Clear and Test

   Reconnect the battery. Use an Electronic Service Tool (EST) to clear the inactive 19040 fault code. Start the engine and allow it to reach operating temperature (or perform a stationary regeneration) to verify that the sensor reading now matches the ECM's calculated value.