Case IH 3849 – ENGINE ECU (EDC - Electronic Diesel Control module): Zero Fuel Calibration by Lambda (ZFL): DFC reporting error state on comparing energizing time to Min value injector 2.

The engine control unit uses the Lambda (oxygen) sensor to monitor exhaust gases and calibrate the minimum fuel delivery (zero fuel calibration) for each cylinder. The Diagnostic Fault Check (DFC) triggers this code when the energizing time required for Injector 2 hits or drops below the minimum allowable limit. This typically indicates that Injector 2 is mechanically out of specification, contaminated, or leaking (over-fueling), which forces the system to pull the fuel trim down to its absolute minimum limit to compensate.

• Farmall
• SR175
• SR220
• SR250
• SV250
• SV300
• TR320
• TV380
• Farmall 115U Pro EP

1. 1

   Check for air in the fuel system by installing a clear test line at the inlet of the fuel injection pump

2. 2

   Check fuel supply pressure (should not drop below 0.276 bar / 4.0 psi) and vacuum restriction (should not exceed 2 inches of Hg)

3. 3

   Inspect primary fuel pre-filter and secondary fuel filter for restrictions or contamination

4. 4

   Inspect the wiring harness and connectors to Injector 2 for open circuits or shorts

5. 5

   Perform an injector leak-off test to check for excessive return flow or leakage from Injector 2

1. 1

   Resolve Supply Issues

   If air ingress or fuel pressure restrictions were found during diagnostics, repair the low-pressure fuel lines or replace the restricted fuel filters. Clear the code and retest.

2. 2

   Replace the Faulty Injector

   If the fuel supply is clean and the leak-off test confirms Injector 2 is leaking or contaminated (as indicated by the ECU pulling the energizing time to the minimum), remove and replace Injector 2.

3. 3

   Write Injector Calibration Codes

   After installing the new injector, you MUST use a diagnostic service tool (such as the Case IH EST) to write the new injector's specific calibration code (IQA/IMA code) into the Engine ECU. Failure to write the correct injector codes will result in further invalid code errors (e.g., code 3705).

4. 4

   Test Run

   Run the machine under load to ensure the Lambda sensor can verify the new zero fuel calibration and confirm the fault code does not return.