John Deere 676.14 – Engine Control Unit (ECU): Cold Start Aid / Glow Plug Relay Circuit Fault

The ECU detects a voltage mismatch in the relay circuit (either shorted to ground or output voltage high when not energized). The ECU restricts or disables the cold start aid function to prevent damage, which can result in hard starting in cold weather.

• 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
• 210G
• 210GLC
• 300GLC
• compact models
• 6090MC
• 6090RC
• 6100MC
• 6100RC
• 6110MC
• 6110RC
• John Deere 6090 Diesel Engine (Level 24 ECU)

1. 1

   Visually inspect the cold start aid relay (glow plug relay) and its wiring for signs of physical damage, frayed wires, or melted insulation.

2. 2

   Inspect the engine harness-to-glow plug interface 3-pin connector (X5004) for damage, corrosion, or oil/debris intrusion.

3. 3

   Use a multimeter to measure the resistance in the relay circuit and check for continuity to ground to locate potential short circuits.

4. 4

   Test the relay to see if it activates unexpectedly or fails to activate when the ECU sends the command.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the battery to prevent electrical shorts during repair.

2. 2

   Clean Connectors

   If oil or debris is found in the engine harness connectors (a known issue on some GLC excavators), thoroughly clean out the connectors with electrical contact cleaner and reattach them.

3. 3

   Repair Wiring

   If a short to ground is found during the multimeter test, repair or replace the damaged section of the glow plug harness (e.g., harness W40). Ensure all connections are secure and properly insulated.

4. 4

   Replace the Relay

   If the wiring is intact but the relay fails bench testing (e.g., internal short or stuck contacts), replace the glow plug relay.

5. 5

   Clear Codes and Test

   Reconnect the battery. Cycle the power to the tractor/machine to reset the ECU. Start the engine and verify that the cold start timer functions normally and the 000676.14 code does not return.