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Failed Smog Test

2000 Infiniti I30 with trouble code P0171 and P0174. What does this mean?

My Infinity passed the smog test and less than 400 miles it failed; only 3 months between smog checks, it mechanically possible? The check engine light also came on less than 50 miles since the last smog test. What will need to be repaired to turn of the check engine light and to correct trouble codes P0171 & P0174?


P0171 and P0174 indicate your Infinity is running lean in both Bank 1 and Bank 2. Bank 1 and 2 refer to the engine's number one cylinder side and the opposing side. Running "lean" means either not enough fuel is getting to the combustion chambers, or too much air is being mixed in with the fuel. First you'll need to look into things which would cause unmetered air to enter the intake manifold, such as cracked or disconnected vacuum hoses. Second you should inspect things which would cause inadequate fuel delivery such as emission sensors which may be reporting false values to the ECU (engine control computer). A good example of an emission component would be a defective MAF (Mass Air Flow Sensor). A good example of a mechanical component would be a dirty fuel filter or weak fuel pump.

posted by SmogTips Support 11-16-2011 05:10 PM

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