Case IH 17912 (F-3512-04) - ECU – Engine Control Unit (ECU) / Engine Control Module (ECM): ECU 5 volt sensor supply 4 high side output driver shorted to ground failure

The Engine Control Unit (ECU) provides a steady 5-volt reference signal (Supply 4) to power specific engine and cab sensors—most notably the Accelerator Pedal Position Sensor (or throttle position potentiometer). This code triggers when the ECU detects that the voltage on this specific circuit has dropped below the normal operating range (near 0 volts), indicating that the circuit is shorted to ground (a low source). This can be caused by a failed sensor pulling the voltage down, a chafed wire shorting against the chassis, or a failed internal driver inside the ECU.

• VESTRUM CVX
• Case IH Farmall series (e.g., 115U, 40-50 CVT)
• Case IH MXM and MXU series (e.g., MXM120-190, MXU100-135)
• Case IH Axial-Flow Combines (e.g., 5088, 6088, 7088)
• Case IH Steiger and Magnum tractors

1. 1

   Isolate the Sensor: Disconnect the Accelerator Pedal Position Sensor (and any other sensor on the Supply 4 circuit). Turn the key to the ON position (engine off) and measure the voltage at the harness connector for the 5V supply pin.

2. 2

   Check for Internal Sensor Short: If the 5-volt supply returns to normal (approx. 5V) at the connector after unplugging the sensor, the sensor itself has an internal short to ground and must be replaced.

3. 3

   Check the Wiring Harness: If the voltage remains low or at 0V with the sensor unplugged, the short is in the wiring harness or the ECU. Perform a continuity test on the Supply 4 wire between the sensor connector and the ECU pin. Check for continuity to ground (which would confirm a shorted wire).

4. 4

   Inspect Connectors: Thoroughly inspect the ECU and sensor connectors for moisture, corrosion, or bent pins that could be bridging the 5V supply to a ground pin.

1. 1

   Disconnect Power

   Turn off the ignition key and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Expose the Harness

   Trace the wiring harness from the Accelerator Pedal Position Sensor back to the ECU. Look for areas where the harness rubs against the engine block, cab mounts, or chassis.

3. 3

   Repair Wiring (If Applicable)

   If a chafed or pinched wire is found on the 5V Supply 4 circuit, cut out the damaged section. Solder and heat-shrink a new piece of wire, or use an approved OEM weather-sealed butt connector. Wrap the repaired section in protective loom.

4. 4

   Replace the Sensor (If Applicable)

   If the diagnostic checks proved the sensor was pulling the voltage down, unbolt the faulty Accelerator Pedal Position Sensor from the pedal assembly. Install the new sensor and plug in the connector.

5. 5

   Test the ECU

   If the wiring is perfectly intact and the sensor is unplugged, but the ECU still fails to output 5 Volts on the Supply 4 pin, the ECU's internal high-side output driver is permanently damaged. The ECU will need to be replaced and flashed by a dealer.

6. 6

   Clear Codes

   Reconnect the battery, turn the key ON, and use a diagnostic tool to clear the inactive 17912 / 3512-04 fault codes. Test the throttle response to ensure normal operation.