Case IH 59 – Electronic Management Unit (EMU): Microprocessor Reference Voltage Open Circuit

The 5-volt reference voltage circuit supplied by the microprocessor to various sensors has an open circuit, or the value is falling outside of the expected operational range.

• MXM
• MXM 120
• MXM 130
• MXM 140
• MXM 155
• MXM 175
• MXM 190
• TM Series
• TS Series

1. 1

   Perform a Key Cycle Retest by turning the key OFF, then ON to see if the code clears

2. 2

   Enter diagnostic mode H9 on the instrument cluster to inspect for intermittent connector pin faults

3. 3

   Locate and check Fuse 14 for a blown fuse interrupting the voltage supply

4. 4

   Inspect the wiring harness and connectors for damage, loose pins, or an open circuit, and perform a wiggle test to check for intermittent circuit drops

5. 5

   Verify that the system is receiving the correct +12 Volts supply to the module

1. 1

   Repair Wiring/Fuses

   If an open circuit is found during the wiggle test, repair or replace the affected section of the wiring harness. If Fuse 14 is blown, replace it and retest.

2. 2

   Replace the Microprocessor/EMU

   If the wiring, connectors, and fuses are all intact but the reference voltage is still open, the internal microprocessor has failed. You must remove and replace the Electronic Management Unit (EMU).

3. 3

   Recalibrate the System

   Because replacing the microprocessor resets the non-volatile memory, you must perform a full Transmission/EDC Calibration Set Up Procedure after installing the new EMU. Ensure the tractor is at operating temperature (20–50°C for 24x12 transmissions). Apply the parking brake, turn off the A/C, and deselect all electrical/hydraulic services. Run the H1 Clutch and Synchroniser Calibration via the electronic service tool or the tractor's H-menu.