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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative terminal of the battery to prevent electrical shorts.
• Gather essential tools such as a socket set, OBD-II scanner, multimeter, and vacuum gauge.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  1. Visually inspect all vacuum hoses connected to the intake manifold and throttle body for cracks or disconnections.
  2. Use a smoke machine or carburetor cleaner to check for leaks around the intake manifold gaskets and vacuum lines.
  3. Replace any damaged hoses or gaskets as necessary.

3. Clean or Replace MAF Sensor

• Sub-steps:
  1. Locate the MAF sensor in the air intake duct.
  2. Disconnect the electrical connector and remove the MAF sensor from the duct.
  3. Clean the sensor with MAF cleaner spray; do not touch the sensor element.
  4. If cleaning does not resolve the issue, replace the MAF sensor with a new one.

4. Inspect and Repair Fuel System

• Sub-steps:
  1. Check the fuel pressure using a fuel pressure gauge; it should match manufacturer specifications (typically around 50-60 psi).
  2. Inspect the fuel injectors for clogs or leaks; clean or replace them as necessary.
  3. Replace the fuel filter if it is clogged or has not been changed as per the maintenance schedule.

5. Replace Oxygen Sensors (if necessary)

• Sub-steps:
  1. Use an O2 sensor socket to remove the upstream and downstream oxygen sensors from the exhaust system.
  2. Install the new oxygen sensors and ensure they are properly torqued to manufacturer specifications.