Case IH 17898 (F-3509-06) - ECU – Engine Control Unit (ECU / ECM): ECU 5 volt sensor supply 1 high side output driver over temperature failure

The Engine Control Unit (ECU) is detecting excessive heat on the internal driver that supplies 5 volts to the first bank of engine sensors. This is almost always caused by an excessive current draw, such as a short circuit to ground in the wiring harness or a failed sensor that is pulling too much current and overloading the ECU's internal circuitry.

• VESTRUM CVX
• Case IH Austoft 9900
• Various Case IH tractors and equipment running FPT electronic injection engines

1. 1

   Perform a Sensor Isolation Test: Disconnect sensors on the 5 Volt Sensor Supply 1 circuit (e.g., Intake Manifold Pressure/Temperature Sensor, Fuel Delivery Pressure Sensor, Oil Pressure Sensor) one by one. If the fault code changes state, the last sensor disconnected is internally shorted.

2. 2

   Inspect the engine wiring harness for chafed, melted, or pinched wires on the 5V supply lines shorting directly to the chassis ground or engine block.

3. 3

   Disconnect the ECU harness connectors and inspect the pins for the 5V supply circuit for water intrusion, corrosion, or bent pins that could be bridging circuits.

1. 1

   Disconnect Battery Power

   Always disconnect the machine's battery before repairing wiring or replacing the ECU to prevent further electrical damage.

2. 2

   Repair/Replace Wiring

   If a short to ground was found in the harness during diagnostics, repair the damaged wire using OEM-approved splicing techniques, or replace the affected harness section.

3. 3

   Replace Faulty Sensor

   If a specific sensor was found to be pulling down the 5V reference circuit, remove and replace that sensor. Clear the codes and cycle the key to verify the fault does not return.

4. 4

   Replace the ECU

   If the wiring harness tests perfectly (no shorts to ground) and all sensors are unplugged but the ECU still logs an internal 'high side output driver over temperature' failure, the ECU's internal driver is permanently burned out. The ECU must be replaced and flashed/calibrated by a Case IH dealer.