New Holland 3222 – ECU: DEF Injector Control Circuit Fault

This fault code indicates a warning condition on Bank 2 of the engine's after-treatment system. It most commonly cross-references with SPN 3222, FMI 5, which points to an open circuit or lower-than-normal current in the Diesel Exhaust Fluid (DEF) Injector Control Circuit. This disrupts the DEF injector's operation, negatively impacting the emission reduction system and engine performance. In some Cummins engine applications, this code may instead refer to a fault in the Aftertreatment #1 Intake Gas Sensor Heater circuit.

• T8.xxx Series

1. 1

   Check for other active or stored fault codes related to the after-treatment system, NOx sensors, or power supply to provide additional context

2. 2

   Verify battery and system voltage is fully charged (above 12.5V) and ensure all main power and ground connections to the chassis and ECU are clean, tight, and free of corrosion

3. 3

   Visually inspect the wiring harness and connectors leading to the DEF injector (doser module) for chafing, breaks, melting, or corrosion

4. 4

   Inspect the entire after-treatment system harness, including connections to NOx sensors and the SCR system, for similar damage

1. 1

   Turn keyswitch OFF

   Ensure the vehicle's power is off before disconnecting any components.

2. 2

   Disconnect DEF injector

   Disconnect the electrical connector from the DEF injector/doser module.

3. 3

   Test DEF injector solenoid

   Using a multimeter, test the DEF injector solenoid for the correct resistance. Compare the reading to the OEM specifications for that part. An out-of-spec reading indicates a faulty injector.

4. 4

   Test wiring harness

   Check for continuity and for shorts to power or ground in the wiring harness between the Engine ECU and the DEF injector connector. Check for an open circuit (no continuity) on both the power and ground wires. Check for a short circuit by testing for continuity between each wire and the chassis ground. Check for a short to power by testing for voltage at the connector with the key on (if applicable to the circuit design).

5. 5

   Repair or replace damaged wiring

   If any damage, open circuits, or shorts are found in the wiring harness, repair or replace the affected section.

6. 6

   Replace DEF injector

   If the DEF injector solenoid is confirmed to be faulty, it must be replaced.

7. 7

   Check Engine Control Module (ECM)

   If the injector and wiring are confirmed to be good, the issue may lie with the ECM itself, though this is the least likely cause. A check for software updates or further diagnostics by a certified technician may be required.

8. 8

   Clear codes and verify repair

   After completing repairs, reconnect all components, clear the fault codes using a diagnostic tool, and operate the vehicle to ensure the fault does not return.