what causes a P0128 code in a Toyota Corolla E170 (2013-2019)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the engine is cool to avoid burns.
• Disconnect the negative battery terminal.

2. Inspect and Replace the Thermostat

1. Locate the thermostat: Follow the upper radiator hose to the engine to find the thermostat housing.
2. Remove the thermostat housing:
   • Use a socket set to remove the bolts securing the housing.
   • Gently pry the housing off without damaging the gasket.
3. Inspect the thermostat:
   • Check if it is stuck open (should not allow coolant to pass when cold).
   • If faulty, replace it with a new thermostat of the same specifications.
4. Reassemble:
   • Clean the mating surfaces of the thermostat housing and engine.
   • Install a new gasket (if applicable) and torque the housing bolts to the manufacturer’s specifications.

3. Replace the Coolant Temperature Sensor

1. Locate the coolant temperature sensor: It is usually near the thermostat housing.
2. Disconnect the wiring harness from the sensor.
3. Remove the sensor using a socket or wrench.
4. Install the new sensor:
   • Apply a small amount of thread sealant if required.
   • Torque to the manufacturer's specifications.
5. Reconnect the wiring harness.

4. Refill and Bleed the Cooling System

1. Refill the cooling system with the appropriate type and mixture of coolant.
2. Bleed any air from the system by running the engine with the radiator cap off until the thermostat opens and the coolant circulates.
3. Replace the radiator cap securely.

5. Reconnect Battery

• Reconnect the negative battery terminal.