John Deere 000676.03 – ECU / CCU: Cold Start Relay Signal When Relay Should Be Off

The control unit detects a voltage signal from the cold start relay when it should be de-energized. This indicates that the cold start relay circuit is closed or energized unexpectedly, which can be caused by a relay stuck in the closed position, a short circuit providing continuous power to the relay's control or load circuit, or an internal fault within the control module.

• 5065M
• 5075M
• 5085M
• 5095M
• 5095MH
• 5105M
• 5015ML
• 5050E
• 5058E
• 5067E
• 5075E

1. 1

   Verify battery and electrical system health, including load capacity and clean battery terminals or ground connections.

2. 2

   Inspect fuses related to the engine control or cold start circuits (located behind the operator's seat on 5M series).

3. 3

   Note and clear fault codes through the tractor's display, then operate the tractor to see if the code returns as an active (hard) fault.

4. 4

   Visually inspect the wiring harness and connectors associated with the cold start system for chafing, melting, or corrosion.

1. 1

   Locate the cold start relay

   Find the K41 Cold Start Relay, typically located on the firewall or behind a panel under the steering column.

2. 2

   Test the cold start relay

   With the key off, disconnect the relay and check for continuity between the switched terminals (should be none). Apply voltage to control terminals (typically 85 and 86) to verify it clicks and establishes continuity on the switched terminals (typically 30 and 87). Replace the relay if it fails either test.

3. 3

   Test the relay circuit

   With the key off and relay removed, check for voltage at the relay socket's control circuit pin from the ECU/CCU (should be none). Verify the ground connection. Check the high-current side for constant battery power on one terminal and no power on the terminal leading to the cold start aid.

4. 4

   Diagnose control unit

   If the relay and wiring are in good working order, the fault may lie within the Engine Control Unit (ECU) or Chassis Control Unit (CCU). This requires specialized diagnostic equipment and should be performed by a qualified dealer technician.