Case IH 19284 – DeNOx (Selective Catalytic Reduction SCR) Controller / Dosing Control Unit (DCU15): Filterbox heater - short circuit to ground

Malfunction in the Selective Catalytic Reduction (SCR) / Diesel Exhaust Fluid (DEF) system where the electrical circuit that supplies power to the DEF filter box heater has a short circuit to the chassis ground.

• Tier 4a
• Puma 125
• Puma 210
• MX210
• MX230
• MX255
• MX285
• T7.220
• T7.235
• T7.250
• T7.260
• T7.270

1. 1

   Visually inspect the wiring harness running from the SCR Dosing Control Unit (DCU) to the DEF filter box heater for chafed insulation, pinched wires, or melted loom.

2. 2

   Disconnect the electrical connector at the filter box heater and measure the resistance between the heater's power terminal and the chassis ground to check for an internal short.

3. 3

   With the heater disconnected, test the harness side of the connector for a short to ground to determine if the issue lies within the wiring harness.

4. 4

   Inspect the pins on both the harness and the heater for corrosion, moisture intrusion, or bent pins that could bridge the circuit to ground.

1. 1

   Power Down

   Turn off the tractor, remove the key, and disconnect the negative battery terminal to prevent electrical spikes.

2. 2

   Access the DEF Filter Box

   Locate the DEF supply module/filter box assembly (typically mounted near the DEF tank).

3. 3

   Address the Short

   If the harness is shorted: Repair the chafed wire using appropriate weather-sealed heat shrink connectors, or replace the damaged section of the SCR wiring harness. Reroute the harness away from sharp frame edges. If the heater is internally shorted: Unplug the electrical connector, remove the retaining hardware securing the filter box heater, and extract the faulty heater element. Install the new heater and torque the fittings to OEM spec.

4. 4

   Reassembly

   Reconnect the electrical connector, ensuring the weather seal is intact. Reconnect the battery.

5. 5

   Clear Codes

   Turn the key to the ON position. Use the CNH Electronic Service Tool (EST) or the tractor's onboard 'H Menu' (via the instrument cluster diagnostic mode) to clear the stored fault codes from the EEPROM.

6. 6

   Verify Repair

   Start the engine and monitor the SCR system to ensure code 19284 does not return and that the DEF system builds appropriate pressure.