how to fix P0128 coolant temperature too low on Ford Explorer Sixth Generation (2020-present)

Ford Explorer Sixth Generation (2020-present)

Error Codes

2-4 hours

Time

medium

Difficulty

medium

Severity

Error Code: P0128

4 min read

688 words

Problem Statement

Learn how to diagnose and fix P0128 coolant temperature too low issue in Ford Explorer (2020-present). Step-by-step guide with diagnostic procedures and repair instructions.

Error Code

P0128

Affected Component

Cooling System

Estimated Time

2-4 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect battery before working on electrical systems
•Allow engine to cool completely before starting work
•Wear safety glasses when working with coolant

Symptoms

•Check engine light illuminated
•Engine may take longer to reach operating temperature
•Poor fuel economy
•Rough idle when cold
•Heater performance may be inadequate

Diagnostic Steps

1
Use an OBD-II scanner to confirm the P0128 code and check for any additional trouble codes.
2
Inspect the coolant level in the reservoir and radiator, ensuring it is at the proper level.
3
Check the thermostat operation by feeling the upper radiator hose; it should warm up as the engine reaches temperature.
4
Inspect the coolant temperature sensor connector and wiring for any signs of damage or corrosion.
5
Verify the functionality of the engine cooling system, including the water pump and radiator.
6
Test the coolant temperature sensor using a multimeter to ensure it is functioning within specifications.

Solution

💡 Expert Tip

For complex repairs like this, consider taking photos at each step. This helps if you need to reverse a step or consult with a mechanic. Also, keep all removed parts organized - you may need to reference them during reassembly.

Verification

After completing the repair, verify that the issue has been resolved:

✓Test the affected component to ensure it functions correctly
✓Check for any error codes or warning lights
✓Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

•Follow the manufacturer's recommended maintenance schedule
•Address warning signs early before they develop into major issues
•Use quality parts and fluids recommended for your vehicle
•Keep detailed records of all repairs and maintenance

Tools & Equipment Required

•OBD-II scanner
•Socket set
•Multimeter
•Drain pan
•Wrench
•Thread sealant

Parts Required

•Thermostat
•Coolant temperature sensor

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Diagnostic Steps

1
Use an OBD-II scanner to confirm the P0128 code and check for any additional trouble codes.
2
Inspect the coolant level in the reservoir and radiator, ensuring it is at the proper level.
3
Check the thermostat operation by feeling the upper radiator hose; it should warm up as the engine reaches temperature.
4
Inspect the coolant temperature sensor connector and wiring for any signs of damage or corrosion.
5
Verify the functionality of the engine cooling system, including the water pump and radiator.
6
Test the coolant temperature sensor using a multimeter to ensure it is functioning within specifications.

Solution

1. Preparation

Gather necessary tools and parts.
Disconnect the battery to prevent electrical shorts.
Allow the engine to cool completely before starting work.

2. Replace Thermostat

Locate the Thermostat: Find the thermostat housing, typically situated where the upper radiator hose connects to the engine.
Remove Components: If necessary, remove any components obstructing access to the thermostat (e.g., air intake ducts).
Drain Coolant: Place a drain pan under the radiator and open the drain valve to remove some coolant (about a gallon) to prevent spillage.
Unbolt Thermostat Housing: Using a socket set, remove the bolts securing the thermostat housing and carefully lift it off.
Remove Old Thermostat: Take out the old thermostat and inspect the sealing surface for any corrosion or damage.
Install New Thermostat: Place the new thermostat in the housing, ensuring it's oriented correctly (usually with the spring side facing the engine).
Reassemble: Reattach the thermostat housing, torque the bolts to the manufacturer's specifications, and reconnect any components removed earlier.

3. Replace Coolant Temperature Sensor (if needed)

Locate the Sensor: Identify the coolant temperature sensor, typically located near the thermostat or on the engine block.
Disconnect Electrical Connector: Carefully unplug the sensor’s electrical connector.
Remove Sensor: Use a wrench to unscrew the old sensor from its location.
Install New Sensor: Apply a small amount of thread sealant to the new sensor's threads and install it by hand. Tighten it with a wrench to the manufacturer's specifications.
Reconnect Connector: Plug the electrical connector back onto the new sensor.

4. Refill Coolant

Close Drain Valve: Ensure the radiator drain valve is closed.
Refill Coolant: Pour the proper mixture of coolant and water into the radiator and reservoir until full.
Bleed the Cooling System: Start the engine with the radiator cap off and allow it to reach operating temperature, adding coolant as needed to remove any trapped air.

5. Final Checks

Reconnect Battery: Reconnect the battery terminals.
Check for Leaks: Inspect the cooling system for any leaks around the thermostat and sensor.
Perform a Test Drive: Monitor the engine temperature and heater performance during a test drive.