how to fix P0135 code in Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Park the vehicle on a flat surface and engage the parking brake.
• Disconnect the negative battery terminal to ensure safety while working on electrical components.

2. Inspect Wiring and Connections

• Remove the engine cover if necessary to access the upstream oxygen sensor.
• Visually inspect the wiring harness and connectors for signs of damage, such as fraying, corrosion, or loose connections.
• If damage is found, repair or replace the wiring/connectors as needed.

3. Replace the Oxygen Sensor

• Locate the upstream oxygen sensor (usually near the engine exhaust manifold).
• Use an oxygen sensor socket or a wrench to carefully unscrew and remove the faulty oxygen sensor.
• Apply anti-seize compound to the threads of the new oxygen sensor.
• Install the new oxygen sensor by threading it into the exhaust pipe and tightening it to the manufacturer's specifications (typically around 30 ft-lbs).
• Reconnect the wiring harness to the new oxygen sensor.

4. Check the Heater Circuit

• Using a multimeter, check the voltage at the oxygen sensor connector with the ignition on (engine off). The reading should be around 12V.
• If the voltage is not present, trace the wiring back to the fuse and ECM to find and repair any breaks or shorts.

5. Clear the Code and Test

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0135 code.
• Start the engine and allow it to reach operating temperature.
• Take the vehicle for a test drive to ensure that the check engine light does not illuminate again.