Case IH 19020 – DCU (Dosing Control Unit): Temperature sensor before catalyst (electrical) | signal low | Catalyst Temperature Sensor Circuit Low

The voltage signal coming from the upstream exhaust gas temperature sensor (located before the SCR/catalyst) has dropped below the acceptable threshold. This indicates a short circuit to ground within the sensor wiring, a disconnected/broken wire, or an internally shorted/failed temperature sensor.

• Tier 4a
• Tier 4b
• Case IH Magnum Series: 235, 260, 290, 315, 340 (Series 4)
• Case IH Steiger / Quadtrac Series: 350, 400, 450, 500, 550, 600 (NA and QT models)
• Case IH Puma Series
• Case IH Rowtrac Series

1. 1

   Perform a plausibility check using an Electronic Service Tool (EST) or diagnostic scanner to read live temperature data on a cold engine (should match ambient temperature).

2. 2

   Visually and physically inspect the wiring harness leading from the DCU to the upstream catalyst temperature sensor for chafed wires, melted insulation, or corrosion inside connector pins.

3. 3

   Ensure the exhaust gas piping and muffler are mounted correctly and are not physically damaged, checking for exhaust leaks before the sensor.

1. 1

   Test and Repair Wiring

   Check the wiring harness for continuity and shorts to ground using a multimeter. If a short or break is found in the wiring, repair the damaged section or replace the affected cable harness.

2. 2

   Replace the Sensor

   If no errors in the wiring or connections can be found, the fault lies within the sensor itself. Remove the old temperature sensor from the exhaust pipe (before the catalyst) and install a new sensor.

3. 3

   Retest

   Clear the fault codes using your diagnostic tool and run the engine to operating temperature to verify the code does not return.

4. 4

   Module Replacement

   If the wiring is perfectly intact and a new sensor does not clear the 'signal low' code, the internal circuitry of the DCU (Pump Module) has failed. The pump module/DCU will need to be replaced and reprogrammed.