Skip the auto shop - Our mechanics make house calls

Q: Pulled codes, says engine running lean.

asked by on

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.

A: The O2 sensors lean codes in most cases are...

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.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Possible broken axle

I think you are dead on about the axle. What has probably happened is that the CV joint has separated. The CV joint is a ball and groove affair that allows the power to be transmitted through the shaft while...

Q: Brakes hard to push pedal when cold not stoping very good after warm they work better

Hi there. From the description you have provided, your vehicle's hard brake pedal is a safety concern. It could be, the power brake booster check valve is faulty. It could be, the brake booster itself, is at fault. A hissing...

Q: Loss of power won't go over 35 mph - 1999 Dodge Ram 1500

This may be a sign of low fuel pressure, a failing mass air flow sensor or potentially a clogged catalytic converter. As you may already know, the catalytic converter converts toxic exhaust gases into less harmful pollutants that are suitable...

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...