how to fix the P0128 code on my Toyota Corolla E140 (2006-2013)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the engine is cool before starting work to avoid burns.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Replace the Thermostat

• Tools Required: Socket set, torque wrench, gasket scraper, coolant catch pan.
• Sub-steps:
  1. Drain the engine coolant into a catch pan by removing the drain plug from the radiator.
  2. Remove the upper radiator hose from the thermostat housing.
  3. Unbolt the thermostat housing using the socket set and remove it from the engine.
  4. Remove the old thermostat and inspect the housing for any debris; clean if necessary.
  5. Install the new thermostat (ensure it is oriented correctly) and a new gasket.
  6. Reinstall the thermostat housing and torque the bolts to manufacturer specifications (typically around 15-20 ft-lbs).
  7. Reconnect the upper radiator hose.

3. Replace the Coolant Temperature Sensor (if necessary)

• Tools Required: Socket set, wrench set.
• Sub-steps:
  1. Locate the coolant temperature sensor, typically near the thermostat housing.
  2. Disconnect the electrical connector from the sensor.
  3. Unscrew the old sensor using a socket or wrench.
  4. Install the new sensor, ensuring it is tightened to the manufacturer’s specification (usually around 15-20 ft-lbs).
  5. Reconnect the electrical connector.

4. Refill Coolant and Check for Leaks

• Tools Required: Funnel, coolant.
• Sub-steps:
  1. Refill the engine coolant through the radiator cap using a funnel until the correct level is reached.
  2. Start the engine and allow it to reach operating temperature while checking for leaks around the thermostat and sensor.
  3. Top off any coolant as necessary.