how to fix P0174 code on my Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, vacuum gauge, basic hand tools, cleaning supplies (throttle body cleaner), safety glasses, gloves.
• Disconnect the negative battery terminal to ensure safety while working.

2. Inspect for Vacuum Leaks

• Sub-steps:
  1. Visually inspect all vacuum hoses connected to the intake manifold for cracks or disconnections.
  2. Use a vacuum gauge to test for leaks in the intake system.
  3. If a leak is found, replace or repair the affected hoses or gaskets.

3. Check and Clean the MAF Sensor

• Sub-steps:
  1. Locate the MAF sensor, typically found between the air filter and throttle body.
  2. Disconnect the electrical connector from the MAF sensor.
  3. Remove the MAF sensor from the air intake duct.
  4. Clean the MAF sensor with MAF cleaner (do not touch the sensor elements).
  5. Reinstall the MAF sensor and reconnect the electrical connector.

4. Inspect Fuel Delivery System

• Sub-steps:
  1. Check the fuel pressure using a fuel pressure gauge; compare with manufacturer specifications.
  2. If pressure is low, inspect the fuel pump and fuel filter for blockages or failures.
  3. Replace the fuel filter if it is clogged.

5. Examine Oxygen Sensors

• Sub-steps:
  1. Visually inspect the oxygen sensors for damage or corrosion.
  2. Use a multimeter to check the voltage output of the upstream and downstream oxygen sensors.
  3. Replace any malfunctioning sensors as necessary.

6. Reassemble and Clear Codes

• After completing all repairs, reconnect any components that were disconnected.
• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear any stored codes.