Case IH F-3509-12 - ECU – Engine Control Module (ECM / ECU): ECU Power Stage 1: Error Sensor supply for sensors / ECU 5 volt sensor supply 1 out of range failure

The Engine Control Module (ECM) provides a steady 5-volt reference signal to a specific group of engine sensors (known as Sensor Supply 1). This fault code triggers when the voltage on this circuit falls out of the expected range. This is almost always caused by a short circuit to ground, a short to battery voltage in the wiring harness, or an internally shorted sensor pulling the entire 5V circuit down.

• MAGNUM AFS Connect
• Austoft 9900 sugarcane harvesters
• Magnum series tractors
• Steiger series tractors
• Puma series tractors
• Optum series tractors
• Skid Steer Loaders (e.g., SR130, SR160, SV185)

1. 1

   Verify system voltage by checking the battery voltage and alternator output to ensure the main system voltage is stable.

2. 2

   Isolate the sensors on the 5V circuit (Boost Pressure, Engine Oil Pressure, EGR Differential Pressure, and Exhaust Gas Pressure) by disconnecting them one at a time while monitoring the 5V supply circuit with a multimeter. If voltage returns to normal, the unplugged sensor is internally shorted.

3. 3

   Inspect the engine wiring harness for chafing, melted wires, or pinched areas that could cause a short to ground or short to battery on the 5V reference wire.

4. 4

   Test the ECM by disconnecting the ECM harness and testing the specific ECM pins for the 5V supply. If it is not outputting 5V when completely isolated, the ECM has an internal failure.

1. 1

   Turn off the machine, remove the key, and disconnect the negative battery cable.

2. 2

   Locate the internally shorted sensor (e.g., the Boost Pressure Sensor) or the damaged section of the wiring harness.

   Based on your diagnostic isolation test.

3. 3

   Splice and heat-shrink the damaged 5V reference wire.

   If repairing the harness, ensure it is routed away from high-heat sources like the EGR valve or exhaust manifold.

4. 4

   Disconnect the wiring harness pigtail from the faulty sensor, remove the retaining bolts or clips, and pull the sensor from its port.

   If replacing a sensor.

5. 5

   Install the new OEM sensor and torque to the manufacturer's specification.

   Lubricate the O-ring with clean engine oil if applicable.

6. 6

   Reconnect the sensor wiring harness.

7. 7

   Reconnect the battery, turn the key to the ON position, and clear the inactive fault codes.

   Use the CNH Electronic Service Tool (EST) or equivalent diagnostic scanner.

8. 8

   Start the engine and verify the code does not return.

   If the harness and sensors are perfectly fine but the ECU cannot output 5V, the Engine ECU must be replaced and flashed with the correct machine software.