New Holland 3006 – ECU: Coolant Temperature Sensor - Invalid Signal

The Engine Control Unit (ECU) has detected an invalid or implausible signal from the engine's coolant temperature sensor. This is typically flagged when the coolant temperature reading is not logical compared to the engine oil temperature. This discrepancy indicates a fault within the sensor itself, its associated circuit, or its connector, rather than an actual engine overheating condition. The ECU relies on this accurate reading to properly manage fuel injection, engine timing, and cooling system operations like engaging the cooling fan.

• T6000 series
• T6010
• T6020
• T6030
• T6050
• T6070
• T7 series
• T8 series
• TL-A series
• TL80A
• TL90A
• TL100A
• TS-A series
• TS100A
• TS110A
• TS115A
• TS130A
• B90B
• B95
• B95B
• B110
• B110B
• B115
• B115B
• LB75.B
• LB90.B
• LB110.B
• LB115.B
• L180
• L185
• L190
• L223
• L225
• L230
• C185
• C190
• C227
• C232
• C238
• LM series
• M series
• T series
• W series
• LW series
• CR series
• CX series
• D series
• E series

1. 1

   Visually inspect the coolant temperature sensor's wiring harness and connector for any signs of damage, corrosion, or loose connections.

2. 2

   Check for other active fault codes using a diagnostic tool. Codes related to the oil temperature sensor or sensor supply voltage could indicate a wider electrical issue.

3. 3

   Perform a simple unplug test: with the engine running, unplug the coolant temperature sensor. If the cooling fan engages, it strongly suggests the sensor itself has failed.

4. 4

   Perform a wiring and voltage check: disconnect the sensor, turn the ignition key to 'ON' (engine off), and use a multimeter to verify a 5-volt reference signal from the ECU on one pin and a ground on the other.

5. 5

   Perform a sensor resistance test: with the sensor unplugged, measure the resistance (Ohms) across its two pins. Compare to specifications (e.g., 153.9 Ω at 50°C/122°F, 51.9 Ω at 80°C/176°F, 27.4 Ω at 100°C/212°F). A reading of 'OL' (Open Loop) or zero resistance indicates a failed sensor. You can also test the sensor by submerging it in cold and then hot water to see if the resistance changes accordingly; it should be high when cold and low when hot.

1. 1

   Prepare the machine

   Ensure the engine is completely cool to prevent burns and minimize coolant loss. Park the machine on a level surface and engage the parking brake.

2. 2

   Locate the sensor

   Identify the coolant temperature sensor on the engine. It is typically a small, two-pin brass component located on the cylinder head or near the thermostat housing.

3. 3

   Manage coolant

   Depending on the sensor's location, partially or fully drain the engine coolant into a clean container to avoid spillage when the sensor is removed.

4. 4

   Remove the old sensor

   Disconnect the electrical connector. Using an appropriately sized wrench, carefully unscrew and remove the old sensor from the engine block.

5. 5

   Install the new sensor

   Ensure the threads on the new sensor and the engine block are clean. Apply a suitable thread sealant if recommended by the manufacturer. Screw the new sensor into place and tighten it to the specified torque. Do not overtighten.

6. 6

   Reconnect and refill

   Attach the electrical connector to the new sensor. Refill the cooling system with the previously drained coolant or new coolant as required.

7. 7

   Final checks

   Start the engine and let it warm up, checking for any coolant leaks around the new sensor. Use a diagnostic tool to clear the 3006 fault code from the ECU.