Case IH 385 – Engine Control Module (ECM): 5 Volt Sensor Supply voltage is too high.

The Engine Control Module (ECM) supplies a regulated +5 volts to various engine sensors (such as the accelerator pedal position sensor, engine speed sensor, and pressure sensors). This fault is logged when the ECM detects that the voltage on this sensor supply circuit has exceeded the normal threshold (typically sensing more than +5.25 volts). This is usually caused by a short circuit to a higher voltage source (like the 12V battery circuit), a shorted sensor, or an internal failure within the ECM.

• MX Magnum
• STX Steiger
• Case IH MX Magnum Series
• Case IH TG Series Tractors
• Case IH Steiger Series
• Case IH Puma Series
• Case IH AFX Series Combines

1. 1

   Verify the Code: Use a diagnostic scan tool to confirm if Fault Code 385 is currently active or stored in the history.

2. 2

   Sensor Isolation (Shorted Sensor Cause): Disconnect the sensors on the 5-volt supply circuit one at a time (e.g., accelerator pedal position sensor, engine speed sensor, intake manifold pressure sensor). If the voltage returns to normal (5V) and the code goes inactive after unplugging a specific sensor, that sensor is internally shorted.

3. 3

   Harness Inspection (Shorted Wiring Cause): Inspect the engine wiring harness and connectors for chafing, rubbing, or corrosion. Look specifically for areas where the 5-volt supply wire might be shorting against a 12-volt power wire or the battery supply circuit.

4. 4

   ECM Voltage Test (Internal ECM Failure Cause): Disconnect the engine wiring harness from the ECM. Measure the voltage directly at the 5-volt supply pins on the ECM. If the ECM outputs more than 5.25 volts with nothing connected, the ECM has an internal hardware failure.

1. 1

   Disconnect Power

   Turn the key switch to the OFF position and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Repair/Replace the Shorted Component

   If a sensor was at fault: Replace the internally shorted sensor identified during the diagnostic checks. If the harness was at fault: Repair the shorted wires in the engine harness using OEM-approved wiring repair techniques, or replace the entire engine wiring harness if the damage is extensive. If the ECM was at fault: Replace the Engine Control Module.

3. 3

   Clean Connections

   Apply dielectric grease to the repaired connectors to prevent moisture intrusion and corrosion.

4. 4

   Reassemble and Clear Codes

   Reconnect the battery, turn the key ON, and use a diagnostic scan tool to clear the inactive fault codes.

5. 5

   Verification Test

   Start the engine and run it through its normal operating RPM range to verify that Fault Code 385 does not return.