John Deere 5127.04 – Engine Control Unit (ECU): Sensor Supply #9 Voltage Out of Range Low

The supply voltage for the Sensor 9 circuit has dropped below the acceptable lower limit. This condition typically points to a short circuit to ground within the wiring harness or an internal short within one of the sensors powered by this specific supply circuit (such as the Intake Air Temperature Sensor or DOC/DPF Temperature Module).

• 5085E
• 5090E
• 5090EL
• 5100E
• 5090M
• 5100M
• 5100MH
• 5100ML
• 5115M
• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 8R / 8RW Series (8245R to 8400R)
• 9RT Series Track Tractors (9470RT, 9520RT, 9570RT)
• 6MC / 6RC Series (6090MC, 6100MC, 6110MC, 6090RC, 6100RC, 6110RC)
• 6090 Diesel Engine
• 6.8L OEM Diesel Engines
• Custom Truck One Source pullers/tensioners (DPT40-B, PTV100/72)

1. 1

   Inspect wiring and connections associated with the Sensor Supply #9 circuit for damaged, frayed, or loose wires

2. 2

   Check the wiring harness for any points where wires may be rubbing against the engine block or chassis, causing a short to ground

3. 3

   Isolate the short by disconnecting the sensors on the #9 supply circuit (Intake Temperature Sensor, DOC/DPF Temperature Module) one at a time. If the supply voltage returns to normal, the disconnected sensor is internally shorted

4. 4

   Verify that the ECU is outputting the correct reference voltage on the Sensor Supply #9 pin when the harness is disconnected

1. 1

   Power Down

   Turn off the engine and remove the key to ensure the ECU is powered down.

2. 2

   Locate Components

   Locate the sensors powered by Sensor Supply #9 (Intake Air Temperature Sensor, DOC/DPF Temperature Module).

3. 3

   Inspect Connectors

   Disconnect the harness connectors at the sensors. Inspect the pins for corrosion, moisture ingress, or bent terminals. Clean or repair the connectors as necessary.

4. 4

   Repair Wiring

   If chafed or bare wires were found during the diagnostic checks, repair the wiring using an approved John Deere harness repair kit, and insulate the wires to prevent future rubbing.

5. 5

   Replace Faulty Sensor

   If the diagnostic checks proved a sensor was internally shorted to ground, remove the faulty sensor and install the OEM replacement.

6. 6

   Clear Codes and Test

   Reconnect all components, turn the key to the ON position, and use a John Deere Service Advisor diagnostic tool to clear the ECU fault codes. Run the engine and monitor the system to ensure code 005127.04 does not return.