Case IH F-3508-14 - ECU – Engine Control Unit (ECU): Supply UB1 short circuit to battery failure

The Engine Control Unit has detected that the 'Actuator Supply 0' (UB1) circuit is receiving 12/24 volts, indicating a direct short circuit to the battery voltage. This means the power supply line intended to drive specific engine actuators is bypassed or shorted to a constant power source, which can cause erratic actuator behavior or trigger a protective power reduction (limp mode).

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1. 1

   Identify the 'Actuator Supply 0' circuit on the Bosch MD1CE101 ECU, corresponding to pins 2.05, 2.17, 2.18, and 2.19

2. 2

   Disconnect the ECU and the actuators on the UB1 circuit, then use a multimeter to check for continuity between the UB1 wiring harness pins and the positive battery terminal to identify a harness short

3. 3

   Test the individual actuators powered by UB1 for internal shorts to their power supply pins

4. 4

   If the wiring and actuators test perfectly, check if the short is internal to the ECU's power distribution block

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the negative battery cable to prevent electrical damage during testing.

2. 2

   Access the ECU

   Locate the Bosch MD1CE101 Engine ECU (typically mounted on or near the engine block).

3. 3

   Disconnect and Isolate

   Unplug the main harness connectors from the ECU.

4. 4

   Trace the Short

   Using a multimeter, probe pins 2.05, 2.17, 2.18, and 2.19 on the harness side. Trace the wiring loom back toward the actuators and the battery. Look for areas where the wire loom may have rubbed against the chassis, engine block, or another hot wire, causing the insulation to melt or chafe.

5. 5

   Repair Wiring

   If a short is found in the harness, cut out the damaged section of the wire, solder in a new section of equivalent gauge, and seal it with heat-shrink tubing.

6. 6

   Replace Components

   If an actuator is internally shorted, replace it. If the harness and actuators are fine but the ECU is outputting battery voltage erroneously on the ground/control side, the ECU must be replaced.

7. 7

   Reassembly and Clearing Codes

   Reconnect the ECU and battery. Use the Case IH Electronic Service Tool (EST) to clear the F-3508-14 / 3877 fault code and verify that the code does not return upon engine startup.