John Deere 676.31 – Engine Control Unit (ECU): Cold Start Aid Relay Signal Not Received When Expected / Glow Plug Relay Output High When Relay Not Active

The Engine Control Unit (ECU) detects high output voltage on the cold start aid (glow plug) relay circuit when the ECU has not commanded the relay to be active. This indicates that the glow plug relay is stuck closed (active) or the circuit is shorted to power.

• 5085E
• 5090E
• 5090EL
• 5100E
• 5090M
• 5100M
• 5100MH
• 5100ML
• 5115M
• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 3029 PowerTech
• 4045 PowerTech
• 6068 PowerTech
• 8.1L PowerTech
• 9.0L PowerTech
• 12.5L PowerTech
• 210G
• 210GLC
• 17D
• 26G
• 35D
• 50D
• 544K II
• 7R Series
• 7600
• 7700
• 7800
• 7630
• 7830
• 7930
• 5083EN
• compact utility tractors
• STS Series 9560
• STS Series 9670
• STS Series 9770
• STS Series 9870

1. 1

   Cycle the machine's power and restart to see if the relay resets or if the code remains active

2. 2

   Locate the Glow Plug Relay (K16) and check for battery voltage on the relay socket terminals when the machine is on but the engine is warm (when the relay should be off)

3. 3

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

4. 4

   Inspect the Glow Plug Harness (W40) for any exposed wires causing a short to power

1. 1

   Disconnect battery

   Disconnect the battery to ensure safety while working on the high-current glow plug circuit.

2. 2

   Access relay

   Access the fuse/relay panel or the engine compartment where the K16 Glow Plug Relay is mounted.

3. 3

   Test relay

   Remove the glow plug relay and test it with a multimeter. If the internal contacts are welded/stuck closed (showing continuity across the load pins when unpowered), the relay is defective.

4. 4

   Trace circuit and repair harness

   If the relay tests fine, use a multimeter to trace the circuit (e.g., circuit 072 or the W40 harness) back to the ECU to locate the short-to-power in the wiring harness. Repair or replace the damaged section of the wiring harness.

5. 5

   Replace relay

   If the relay is faulty, install a replacement OEM glow plug relay.

6. 6

   Verify repair

   Reconnect the battery, turn the key to the ON position, and verify that the 000676.31 fault code has cleared.