John Deere 000676.06 – ECU: Cold Start Aid Drive Circuit Has Low Resistance

The Engine Control Unit (ECU) has detected abnormally high current in the cold start aid circuit, indicating a low-resistance condition. This is typically caused by a short to ground in the wiring, a failed intake heater element, or a faulty relay. This condition affects the proper operation of the circuit during initial engine startup, which can lead to hard starting in cold weather, rough idling, and excessive white or gray exhaust smoke from unburned fuel.

• 9670 STS
• 9770 STS
• 5045D
• 5055E
• 5075M
• 5100E

1. 1

   Verify symptoms such as hard starting in cold weather, rough idling, or excessive white/gray smoke

2. 2

   Visually inspect the wiring harness leading to the intake air heater and relay for chafed or melted insulation that could cause a short to ground

3. 3

   Test the glow plug/intake heater element resistance using a multimeter (expected: 0.5 to 2.0 ohms; near zero indicates a dead short)

4. 4

   Test the cold start aid relay to ensure it is functioning correctly and not stuck in the closed position

5. 5

   Disconnect the harness from the ECU and relay, then check for continuity to ground on the power supply wire to identify a short circuit in the harness

1. 1

   Disconnect battery

   Disconnect the negative battery terminal to prevent electrical shorts during the repair process.

2. 2

   Locate components

   Identify the intake air heater (typically located on the engine's intake manifold), the relay, and the connecting wiring harness.

3. 3

   Isolate the fault

   Using the results from the diagnostic tests, determine which component (heater element, relay, or wiring) is the cause of the fault.

4. 4

   Repair or replace wiring

   If the wiring harness test confirmed a short to ground, repair the damaged section or replace the entire harness.

5. 5

   Replace relay

   If the relay was found to be stuck closed or otherwise faulty during testing, replace it with a new one.

6. 6

   Replace intake heater element

   If the heater element showed near zero resistance (dead short), replace the intake air heater.

7. 7

   Reassemble and verify

   Reconnect all connectors and the battery terminal. Clear the fault code using a diagnostic tool and start the engine to verify the repair was successful and the code does not reappear.