Case IH 3969 – Engine Control Unit (ECU): Invalid Injector Codes

The injector calibration codes (IQA or trim codes) currently stored in the Engine ECU's memory are invalid, missing, or incorrect.

• skid steer
• Skid Steer Loaders (SSL)
• SR175
• L220
• Compact Track Loaders (CTL)
• Steiger series
• Magnum series

1. 1

   Check service history to determine if the machine recently had an ECU software update, an ECU replacement, or fuel injector replacements.

2. 2

   Locate the fuel injectors on the engine and write down the alphanumeric calibration code printed on the top or side of each injector.

3. 3

   Connect the CNH Electronic Service Tool (EST) to the machine's diagnostic port to read the injector codes currently programmed in the Engine ECU and compare them to the physical codes you wrote down from the injectors.

1. 1

   Connect Diagnostic Tool

   Connect the CNH EST to the machine and turn the ignition ON (engine off).

2. 2

   Access Calibration Menu

   Navigate to the Engine ECU programming or calibration screen within the EST software.

3. 3

   Input Injector Codes

   Enter the correct injector trim/calibration codes (read directly from the installed injectors) into the software for each corresponding cylinder.

4. 4

   Write to ECU

   Save/write the new codes to the Engine ECU.

5. 5

   ECU Reset

   Perform an ECU reset. This usually involves turning the ignition OFF, waiting for the ECU to completely power down (listen for the main relay to click off), and then turning the ignition back ON.

6. 6

   Clear Codes

   Use the EST to clear all stored Diagnostic Trouble Codes (DTCs), including 3969.

7. 7

   Verify Repair

   Start the engine. Verify that the fault code does not return and that the engine runs smoothly without derating.