John Deere 000676.05 – CCU / ECU: Cold Start Relay Voltage Missing

The Engine Control Unit (ECU) is not receiving the expected voltage or signal feedback from the cold start (glow plug) relay when it is supposed to be energized. This indicates an open circuit, short circuit, or malfunctioning component within the glow plug activation system. Without this signal, the cold start system will not operate, leading to difficult or no-start conditions in cold weather.

• 5015ML
• 5065M
• 5075M
• 5085M
• 5095M
• 5095MH
• 5100M
• 5100MH
• 5100ML
• 5105M
• 5115M
• 5115ML

1. 1

   Verify battery health, ensuring it is fully charged and connections are clean and tight

2. 2

   Check for blown fuses, specifically the 70-amp fuse (F030) for the electrical starting aid located on the right side of the engine

3. 3

   Inspect the cold start relay (K046) on the right side of the engine for visible damage, corrosion, or loose connections

4. 4

   Inspect the wiring harness and connections between the cold start relay, temperature sensor, intake air heater element, and the control unit for chafing, breaks, or corrosion

5. 5

   Test the cold start temperature sensor, as a faulty sensor can cause short circuits and blown fuses

1. 1

   Safety First

   Disconnect the battery's negative terminal before beginning any electrical repairs.

2. 2

   Locate Components

   Identify the cold start relay (potentially K046) and its associated fuse (potentially F030) on the right side of the engine. Also, locate the cold start temperature sensor on the engine.

3. 3

   Replace Blown Fuse

   If a blown fuse is found, replace it with a new one of the same amperage rating. Do not use a higher-rated fuse.

4. 4

   Test the Relay

   If the new fuse blows immediately upon turning the key, there is likely a short circuit. Try unplugging the sensor and replacing the fuse again. If the fuse does not blow, the sensor is the likely culprit. If the fuse does not blow, but the fault code persists, test the relay by applying power to its control circuit and checking for continuity across the high-amperage terminals.

5. 5

   Replace Faulty Components

   If the cold start temperature sensor is determined to be faulty, replace it with a new one. If the relay is determined to be faulty, replace it with a new relay of the correct part number and amperage.

6. 6

   Clear Fault Codes

   After the repair is complete, reconnect the battery, start the tractor, and clear any stored diagnostic trouble codes.

7. 7

   Verify Repair

   Operate the tractor to ensure the fault code does not return and that the cold start system functions correctly in appropriate conditions.