How to fix P0174?

Alton Alexander
By Alton AlexanderUpdated on June 4th, 2022

The P0174 code is a generic code that indicates that the engine is running too lean on both banks. This can be caused by several different things, but the most common cause is a vacuum leak. Other possible causes could include a dirty or faulty air filter, a leaking fuel injector, or a faulty mass air flow sensor. If the code is set, the engine will run poorly and may stall.

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1. Check for intake leaks and repair as necessary

  1. Start the car and allow it to idle for a few minutes.
  2. Check the emissions levels.
  3. Inspect the fuel lines for cracks or leaks.
  4. Check the air filters.
  5. Check the coolant levels.
  6. Check the oil levels.
  7. Check the spark plugs.
  8. Check the water pump.
  9. Check the timing belt.
  10. Check the camshaft.
  11. Check the crankshaft.
  12. Check the pistons.
  13. Check the valves.
  14. Check the wiring.

2. Check for exhaust leaks and repair as necessary

  1. Remove the negative battery cable.
  2. Check for exhaust leaks around the engine and exhaust system.
  3. If there are any leaks, repaired as necessary.
  4. Reattach the negative battery cable.

3. Check and clean the MAF sensor

  1. Remove the air cleaner cover.
  2. Locate the MAF sensor on the air cleaner housing.
  3. Inspect the MAF sensor for damage.
  4. If the MAF sensor is damaged, replace the sensor.
  5. Clean the air cleaner housing and MAF sensor assembly with a clean cloth.

If you didn't find success with an option above, then try:

  1. Check and clean the throttle body
  2. Check and replace the O2 sensor
  3. Check fuel pressure and replace the fuel pump if necessary
  4. Check for vacuum leaks and repair as necessary
  5. Replace the PCV valve
  6. Replace the EGR valve