New Holland ENG 3694 – Engine Control Unit (ECU) or Glow Control Unit (GCU): Glow Plugs: Short Circuit to Ground Error for Low Voltage System

The system has detected a short circuit to ground in the glow plug circuit. This can trigger an over-temperature error on the power stage for the glow plug low voltage system. When this code is active, pre-glow and post-glow functions may be disabled, leading to cold starting issues and black smoke.

• L180
• L216
• L220
• L223
• L225
• L228
• C227
• C337
• W50C
• W60C
• W70C
• W80C

1. 1

   Visually inspect wiring and connectors leading to the glow plugs and the GCU for damage, chafing, or melting

2. 2

   Test the wires leading to the glow plugs for a short to ground and check GCU wiring connections for continuity (e.g., pins X-012, X-013, X-079, or X-103)

3. 3

   Check for high system voltage, which is a known failure mode that can trigger this GCU power stage error

4. 4

   Test the individual glow plugs for internal shorts

1. 1

   Disconnect the battery

   Disconnect the battery to ensure safety while working on the low voltage system.

2. 2

   Disconnect the wiring harness

   Disconnect the wiring harness from the glow plugs and the Glow Control Unit / Relay.

3. 3

   Test the engine glow plug harness

   Using a multimeter, test the engine glow plug harness for a short to ground. If the harness is shorted, replace the wire harness.

4. 4

   Test the resistance of each glow plug

   If the harness tests good, test the resistance of each glow plug. If any glow plug is shorted internally or shows out-of-spec resistance, replace the glow plugs (it is highly recommended to replace them as a complete set).

5. 5

   Replace the Glow Plug Relay or GCU

   If both the wiring and glow plugs are functioning correctly, the fault lies within the Glow Plug Relay or the Glow Control Unit (GCU) itself, which must be replaced.

6. 6

   Reconnect components and clear codes

   Reconnect all components, restore battery power, and clear the fault codes using a diagnostic service tool.

7. 7

   Cycle the ignition

   Cycle the ignition to verify if the code (or related codes like 3414, 3415, 3416, or 3417) returns.