John Deere 5127.03 – Engine Control Unit (ECU): Sensor Supply #9 Voltage Out of Range High

The supply voltage for the Sensor 9 circuit is out of range high, which typically points to a short circuit to a 12-volt power source. This circuit provides power to the exhaust aftertreatment temperature sensors (DOC/DPF and SCR Temperature Modules). When active, the engine control system cannot accurately read exhaust temperatures, which may cause the system to limit or adjust engine operation (derate).

• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 8245R
• 8270R
• 8295R
• 8320R
• 8345R
• 8370R
• 8400R
• 9470RT
• 9520RT
• 9570RT
• 5085M
• 5100M
• 5100MH
• 5100ML
• 5115ML
• Equipment utilizing John Deere 6.8L and 9.0L OEM diesel engines

1. 1

   Inspect the wiring harness and connectors associated with Sensor Supply #9 (routing to the DOC/DPF and SCR temperature modules) for damaged, frayed, or loose wiring.

2. 2

   Inspect the circuit for any points where wires may be rubbing against each other or the chassis, causing a short to 12 volts.

3. 3

   Use a digital multimeter or John Deere diagnostic tools to test the temperature modules for proper operation and correct voltage levels.

4. 4

   Ensure that the electrical supply from the ECU to the sensor circuit is stable and within OEM specifications.

1. 1

   Repair Wiring

   If a short to 12V or damaged wiring is found during the diagnostic checks, repair or insulate the wiring harness as needed.

2. 2

   Replace Faulty Module

   If the wiring is intact but the voltage remains out of range, the internal circuitry of the DOC/DPF or SCR Temperature Module has likely failed and must be replaced.

3. 3

   Module Installation

   When installing a new temperature module, apply NEVER-SEEZ (anti-seize compound) to the threads of the sensor probes prior to reinstallation.

4. 4

   Torque to Spec

   Thread the sensor probes into the exhaust filter/DOC/SCR housing and tighten to the specified torque (e.g., 35 N·m or 26 lb.-ft. for M12 exhaust filter temperature sensors).

5. 5

   Clear Codes

   Reconnect the battery/power, turn the key to the ON position, and use a diagnostic tool to reset the ECU and clear the fault code.

6. 6

   Monitor System

   Run the engine and monitor the system to ensure normal operation and verify that the exhaust temperature readings are accurate.