Case IH t74 – Pump Control Unit (PCU): ADC In PCU, Data Valid But Below Normal Range

The plausibility check between the ground and the remaining ADC channels inside the Pump Control Unit fails, and the voltage/data falls below the normal operating range. The Electronic Engine Management (EEM) system forces the engine into limp home mode, restricting maximum engine speed to 1760 RPM to prevent damage.

• MXM
• MXM120
• MXM130
• MXM140
• MXM155
• MXM175
• MXM190
• TM120
• TM130
• TM140
• TM155
• TM175
• TM190

1. 1

   Inspect the main wiring harness connector at the injection pump (PCU) for corrosion, backed-out pins, or moisture

2. 2

   Verify CAN bus wiring between the injection pump (PCU) and the EEM2 controller for continuity and shorts

3. 3

   Check that the engine and PCU ground connections are clean and tight

4. 4

   Temporarily connect a known-good EEM2 controller to isolate the module and rule out a faulty EEM2 sending bad data (Note: this will trigger a mismatch code like FC 175)

1. 1

   Disconnect battery

   Disconnect the tractor's battery to prevent electrical shorts.

2. 2

   Clean injection pump area

   Clean the area around the injection pump on the side of the engine to prevent debris from entering the fuel system.

3. 3

   Disconnect PCU harness

   Disconnect the electrical harness from the PCU.

4. 4

   Remove fuel lines

   Remove the high-pressure fuel injection lines and the low-pressure supply/return lines.

5. 5

   Remove injection pump

   Unbolt and remove the Bosch VP44 injection pump assembly.

6. 6

   Install replacement pump

   Install the replacement injection pump. Crucial: Ensure the engine is at top dead center (TDC) and the pump timing is set exactly to the OEM service manual specifications.

7. 7

   Reinstall lines and harness

   Reinstall the fuel lines and reconnect the PCU electrical harness.

8. 8

   Bleed fuel system

   Bleed the fuel system of all air.

9. 9

   Test run tractor

   Reconnect the battery, clear the t74 fault code using an electronic service tool, and test run the tractor to verify it can exceed the 1760 RPM limp-mode restriction.