John Deere 3512.04 – ECU: Sensor Supply 4 Circuit Fault

The Engine Control Unit (ECU) has detected that the 5-volt reference voltage on Sensor Supply Circuit #4 has dropped below the minimum specification (typically below 4.75 volts). This condition almost always indicates a short to ground in the wiring harness or an internal short within one of the sensors powered by this circuit (such as the Foot Throttle Position Sensor).

• 5085E
• 5090E
• 5090EL
• 5100E
• 5085M
• 5100M
• 5100MH
• 5100ML
• 5115ML
• 5090M
• 5115M
• 310G
• 310J
• 310SG
• 315SG
• 410G
• 710G
• 316GR
• 318G
• 331G
• 333G
• 7R
• 8R
• 8RT
• 9RT
• 7200–7810
• 8100–8520
• 9230–9630
• 444K
• 524K
• 544K
• 624K
• 644K
• 724K
• 744K
• 824K
• 844K
• 4930
• 4940
• 250D–400D
• 670D–872D

1. 1

   Monitor the voltage of the 5-volt Supply 4 circuit using a diagnostic tool (like Service ADVISOR) or a multimeter.

2. 2

   Perform the 'Unplug' test to isolate the short: Unplug the Foot Throttle Position Sensor (or track speed sensors on CTLs). If the 5-volt reference voltage immediately returns to normal (approx. 5.0V), the sensor is internally shorted.

3. 3

   Inspect electrical connections and the wiring harness associated with the 5-volt supply for pinched wires, rubbed-through insulation (shorting to ground), corrosion, or loose pins if unplugging the sensor does not restore voltage.

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Access the Sensor

   Locate the Foot Throttle Position Sensor (usually mounted directly to the throttle pedal assembly in the cab).

3. 3

   Harness Repair (If Applicable)

   If your diagnostic checks revealed a damaged wire (often a red 5V supply wire shorting to ground), splice and heat-shrink the damaged section of the harness, or replace the affected harness pigtail.

4. 4

   Replace the Sensor (If Applicable)

   If the sensor was internally shorted, unbolt the faulty potentiometer from the pedal assembly. Install the new sensor, ensuring the mechanical linkage/tang aligns correctly with the pedal's pivot point.

5. 5

   Reassemble and Reconnect

   Plug the electrical connector back into the sensor. Reconnect the battery.

6. 6

   Clear Codes and Calibrate

   Turn the key to the ON position. Access the machine's service menu (or use Service ADVISOR) to clear the stored 003512.04 code. Some machines may require a quick throttle calibration procedure in the monitor so the ECU can learn the new sensor's 0% and 100% voltage sweeps.