John Deere 412.04 – Engine Control Unit (ECU): EGR Cooled Gas Temperature Signal Voltage is Low

The voltage signal returning from the Exhaust Gas Recirculation (EGR) temperature sensor drops below the normal operating limit. This is almost always caused by the EGR temperature sensor signal wire shorting to ground or the EGR temperature sensor itself completely failing.

• 5085E
• 5090E
• 5090EL
• 5100E
• 5085M
• 5100M
• 5100MH
• 5100ML
• 5115ML
• 5090M
• 5115M
• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 9230
• 9330
• 9430
• 9530
• 9630
• 204L
• 304L
• 540G-III
• 548G-III
• 4930

1. 1

   Inspect the wiring harness leading to the EGR temperature sensor for chafed wires, melted insulation, or pinched lines that could cause a short to ground.

2. 2

   Check the engine coolant level and inspect the radiator/cooling system for debris, as poor EGR cooling can trigger related temperature codes.

3. 3

   Disconnect the sensor and use a multimeter to check the sensor's resistance and the harness voltage. If the harness provides the correct reference voltage but the sensor reads out of specification (or dead short), the sensor is the culprit. If the harness is grounded out, the wiring must be repaired.

1. 1

   Cool Down

   Turn off the engine and allow the exhaust and EGR system to cool completely to avoid severe burns.

2. 2

   Locate the Sensor

   Locate the EGR gas temperature sensor, which is threaded into the EGR cooler or the EGR duct.

3. 3

   Disconnect Harness

   Carefully depress the locking tab and disconnect the electrical harness connector from the EGR gas temperature sensor.

4. 4

   Remove Sensor

   Use the appropriately sized wrench to unthread and remove the faulty EGR temperature sensor from the EGR cooler/duct.

5. 5

   Install New Sensor

   Thread the new EGR temperature sensor into the port and tighten it to the manufacturer's specified torque.

6. 6

   Reconnect

   Reconnect the electrical harness connector until it clicks into place.

7. 7

   Clear Codes

   Turn the key to the ON position and use a diagnostic scan tool to clear the 000412.04 ECU code.

8. 8

   Test

   Start the engine and perform a test drive under load to ensure the code does not return and the EGR system operates normally.