Case IH 19826 – Engine Control Module (ECM) or Aftertreatment Control Module (ACM): Downstream oxidation catalyst temperature sensor voltage is higher than expected

The Engine Control Module (ECM) is reading a voltage signal from the downstream Diesel Oxidation Catalyst (DOC) temperature sensor that exceeds the normal operating range, indicating an open circuit or a short to power in the sensor or its wiring harness.

• Tier 4b
• Farmall 100C
• Farmall 105A
• Farmall 105C
• Farmall 105U
• Farmall 110A
• Farmall 110C
• Farmall 110U
• Farmall 115A
• Farmall 115C
• Farmall 115U
• Farmall 120U
• Maxxum 120
• Maxxum 125
• Maxxum 130
• Maxxum 140
• Puma 140
• 240 Series Axial-Flow Combines
• 5130
• 5140
• 7130
• 7140
• 7150
• 7230
• 7240
• 7250
• 9230
• Case N-Series Tractor Loader Backhoes (TLBs)

1. 1

   Visually inspect the downstream DOC temperature sensor's wiring pigtail and the main engine harness for chafing, melting, or rodent damage.

2. 2

   Disconnect the sensor and check the pins inside the connector for corrosion, moisture, or pushed-back terminals.

3. 3

   Measure the resistance across the two pins of the temperature sensor using a multimeter (an 'OL' or infinite reading indicates a broken internal thermistor).

4. 4

   Turn the key to the ON position (engine off) and measure voltage at the harness-side connector to verify a 5V reference signal and good ground (battery voltage indicates a short to power).

1. 1

   Safety First

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

2. 2

   Locate the Sensor

   Find the downstream DOC temperature sensor. It is threaded into the exhaust piping immediately after the Diesel Oxidation Catalyst chamber.

3. 3

   Disconnect

   Unplug the 2-pin electrical connector connecting the sensor to the engine harness.

4. 4

   Remove the Sensor

   Using a wrench (typically 17mm for the M14x1.5 thread size), carefully loosen and remove the faulty exhaust gas temperature sensor. If it is seized, apply penetrating oil and allow it to soak.

5. 5

   Install the New Sensor

   Apply a small amount of high-temperature anti-seize compound to the threads of the new sensor (if it does not come pre-applied). Thread it in by hand to prevent cross-threading, then tighten it to the OEM torque specification.

6. 6

   Reconnect

   Plug the sensor's electrical connector back into the harness, ensuring it clicks securely into place.

7. 7

   Clear Codes

   Reconnect the battery, turn the key on, and use a diagnostic scan tool (such as the CNH Electronic Service Tool) to clear the 19826 fault code. Start the engine and verify that the code does not return.