P0171 1999 Toyota Camry -

Question

Got the check engine code P0171. There are a few causes for this code.

• Intake air leaks
• Faulty front heated oxygen sensor
• Ignition misfiring
• Faulty fuel injectors
• Exhaust gas leaks
• Incorrect fuel pressure
• Lack of fuel
• Faulty Mass Air Flow (MAF) sensor
• Incorrect Positive Crankcase Ventilation (PCV) hose connection

Please advise on which one should I check and how

Answer 1

P0171 Fuel trim lean Bank 1

Clean the MAF sensor using a MAF cleaning. If you have a intake leak you also have a higher RPM, the normal idle speed is set at 700 RPM +/- 50. Faulty front 02 sensor, unless the signal of the 02 sensor is biased, or there is a exhaust leak just prior to the front 02 sensor, Ignition misfire you have rough idle. Faulty injector , this would set a P0300 random misfire, Incorrect PCV valve this would set a higher than normal RPM. The best solution for this is to clean the MAF sensor.