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Q: Pulled codes, says engine running lean.

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Check engine light has been on for almost 5 months, I've had the codes pulled before found out what the codes were. I re pulled the codes at school, we are lucky to have a scanner along with some other tools, any way got engine running lean for both cylinder banks. My question is what should I check so I can fix the issue?

My car has 145000 miles.
My car has a manual transmission.

The O2 sensors lean codes in most cases are P0171 and P0173. These codes are letting you know that the computer has tried to add fuel to the engine due to the O2 sensors see a lean fuel to air mixture. The computer can only add so much extra fuel then knows something is wrong and sets the lean codes. The engine is getting extra air into the engine that the mass air sensor is not detecting. The extra air can be a leaking intake tube or gaskets in the intake manifold. You should first make sure you have a paper style air filter since the oil type filters will contaminate the mass air sensor causing it to not detect the correct amount of air entering the engine. Clean the mass air sensor, check all the hoses for cracks between the mass air sensor and the throttle body. Scan the mass air sensor for correct readings for your barometric pressure and altitude. The mass air flow sensors are known to register you are at 10,000 feet when you are at 1,000 or less feet. This will lean the mixture with too much air and not enough fuel at your elevation. Replace the mass air sensor if reading is not correct.

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