Q: Engine codes

A number of things may cause code P0171 to be triggered. As the code indicates, this means there is a lean fuel condition which may be caused by a lack of fuel supply or in some cases, a vacuum leak. When a vacuum leak is present, this introduces an excessive amount of air into the fuel/air mixture which results in leaning out the fuel content. Other problems such as a faulty fuel pressure regulator, a faulty fuel pump, a clogged fuel filter, faulty fuel injectors, faulty oxygen sensors, or a faulty mass air flow sensor may also cause this to happen.

Code P0420 relates to the catalyst system not performing properly. This is usually a problem related to the catalytic converter or an oxygen sensor. The catalytic converter converts toxic exhaust gases into less harmful pollutants that are suitable to be expelled into the atmosphere. When the catalytic converter is clogged, this causes these gases to be backed up into the exhaust system not allowing the engine to breathe properly. When this happens, the engine is forced to work much harder to expel these gases. This often results in the engine bogging down, hesitating, shaking and causing very poor fuel economy. This should also cause a check engine light to come on as the O2 sensors should be reading the incorrect amounts of oxygen in the exhaust gases if this is your problem.

Code P1349 relates to the variable valve timing system operating incorrectly. This may be a result of low oil, incorrect valve timing, a malfunctioning variable valve timing control assembly or a faulty ECM. I would suggest having a professional from YourMechanic come to your location to diagnose and inspect your vehicle.