Case IH 17758 (F-3514-12) - ECU – Engine Control Module (ECM): ECM 5 volt sensor supply 6 out of range failure

The Engine Control Module (ECM) has detected an abnormal voltage condition—such as an undervoltage, overvoltage, or a short circuit to ground/battery—on its internal 5-volt reference circuit number 6. This 5V circuit is used to power specific engine sensors. When the voltage is out of range, the ECM cannot trust the signals coming from the sensors on that circuit, which can lead to engine derating or erratic performance.

• VESTRUM CVX
• Farmall
• Maxxum
• Puma
• Optum
• Magnum
• combine harvesters

1. 1

   Verify that the main battery voltage is within normal operating limits to rule out ECU power stage faults.

2. 2

   Perform a sensor isolation drop test by disconnecting sensors on this 5V circuit (primarily the Boost Pressure Sensor) one at a time to see if the 5V reference returns.

3. 3

   Inspect the engine wiring harness between the ECM and the connected sensors for chafing, melting, or pinched wires.

4. 4

   Disconnect the ECM harness and check the pins for corrosion, moisture, or bent terminals.

1. 1

   Power Down

   Turn off the ignition and disconnect the negative battery cable before servicing the ECM or engine wiring.

2. 2

   Locate the Fault

   Based on the diagnostic isolation test, locate the shorted component (either the wiring harness or the Boost Pressure Sensor).

3. 3

   Repair Wiring (If Applicable)

   If the harness is chafed (commonly where it routes near the engine block or EGR components), cut out the damaged section, solder in new wire, and seal it with heat-shrink tubing.

4. 4

   Replace Sensor (If Applicable)

   If the Boost Pressure Sensor is internally shorted, remove the retaining bolt, pull the sensor from the intake manifold, and install a new OEM sensor. Ensure the O-ring is seated correctly.

5. 5

   ECM Replacement (Worst Case)

   If the wiring is completely intact and no sensors are shorted, but the ECM still fails to output 5 volts on the supply 6 circuit, the ECM has suffered an internal power stage failure. The ECM must be replaced and flashed with the correct CNH software payload.

6. 6

   Clear Codes

   Reconnect the battery, connect the CNH Electronic Service Tool (EST), clear the inactive 17758 fault code, and run the engine to verify the 5V supply remains stable.