Case IH 17900 (F-3509-04) - ECU – Engine Control Module (ECM / ECU): ECM 5 volt sensor supply 1 high side output driver shorted to ground failure only

The 5-volt reference circuit 1 is experiencing a short to ground on the high side output driver. Voltage is pulled down below specification, causing all sensors sharing this 5-volt supply to lose power and fail to read correctly.

• VESTRUM CVX
• Austoft 9900 / 9000 Sugar Cane Harvesters
• AFX Combines
• Farmall Tractors
• Steiger / Quadtrac Tractors

1. 1

   Disconnect sensors on the 5V supply 1 circuit one by one (e.g., manifold pressure sensor, throttle valve actuator) to see if the fault goes inactive, indicating an internal sensor short.

2. 2

   Inspect the engine wiring harness between the ECM and the sensors for chafed, rubbed, or pinched wires where the 5-volt supply wire may be touching the chassis or a ground source.

3. 3

   Check the ECM connector pins (e.g., the 60-pin engine connector) for moisture, corrosion, or bent pins that could be bridging the 5-volt driver to a ground pin.

4. 4

   Test the ECM for an internal high side output driver failure if the wiring harness is completely isolated and tests good for continuity without any shorts to ground.

1. 1

   Turn off machine and disconnect battery

   Turn off the machine and disconnect the battery before servicing the ECM or wiring harness.

2. 2

   Replace sensor or repair harness

   Based on the diagnostic results, replace the internally shorted 5-volt sensor, OR repair/replace the damaged section of the engine wiring harness.

3. 3

   Remove defective ECM

   If the ECM itself is diagnosed as internally shorted, remove the defective Engine Control Module.

4. 4

   Install replacement ECM

   Install the replacement ECM. Note that a new or remanufactured ECM will require dealer programming/calibration to match the specific machine and engine configuration.

5. 5

   Reconnect battery and verify

   Reconnect the battery, clear the inactive fault codes from the ECM memory, and run the engine to verify the 5-volt sensor supply 1 circuit is operating within normal voltage parameters.