Case IH 3990 – Engine ECU: ISM-IDI Aftertreatment Burner Injector 2 Short Circuit

This is a Red severity code indicating that the engine control module has detected an excessive current draw on the circuit responsible for operating the #2 aftertreatment burner injector. A high current draw typically means there is a short to ground in the wiring harness or an internal dead-short within the injector's electromagnetic coil.

• skid steer
• SR160
• SR175
• SV185
• L220
• Farmall 30A
• Farmall 35A
• Farmall 30C
• Farmall 35C
• N844LT

1. 1

   Visual Inspection: Inspect the wiring harness running from the Engine ECU to the DPF burner assembly. Look for chafed insulation, melted wires from exhaust heat, or signs of thermal arcing against the engine block.

2. 2

   Connector Check: Disconnect the electrical pigtail at Burner Injector 2. Inspect the pins for corrosion, water intrusion, or melting.

3. 3

   Coil Resistance Test: Using a multimeter, measure the resistance across the two pins on the burner injector itself. A reading of near-zero ohms indicates the injector coil is internally shorted and the injector must be replaced.

4. 4

   Harness Short Test: With the injector unplugged and the battery disconnected, check for continuity between the injector harness power supply wire and a known good chassis ground. If there is continuity, the wiring harness is shorted and must be repaired.

1. 1

   Disconnect Power

   Disconnect the negative battery cable to protect the Engine ECU from further electrical spikes.

2. 2

   Relieve Pressure

   Ensure the machine has cooled down completely. Relieve any residual pressure in the low-pressure fuel lines feeding the aftertreatment burner.

3. 3

   Remove the Injector

   Disconnect the electrical connector and the fuel supply hoses from Burner Injector 2. Remove the mounting hardware securing the injector to the burner housing.

4. 4

   Prep the Housing

   Clean the mounting port on the burner housing, ensuring no old ceramic washer or O-ring material is left behind.

5. 5

   Install the New Injector

   Install the new burner injector. Crucial: You must use the new ceramic washers, insulators, and O-rings provided in the service kit to prevent exhaust gas leaks and heat transfer damage.

6. 6

   Reconnect

   Attach the fuel lines using new hose clips. Reconnect the electrical pigtail.

7. 7

   Clear Codes & Test

   Reconnect the battery. Connect a diagnostic tool (such as CNH EST or TEXA) to clear the 3990 fault code.

8. 8

   Forced Regeneration

   Initiate a forced stationary DPF regeneration via the diagnostic tool to verify that the burner ignites properly, exhaust temperatures reach the target (typically >800°C / 1472°F), and the fault code does not return.