However, I do not see this one very often causing this code. Low fuel pressure can certainly cause the engine to run lean which will obviously flag a P0171 lean code. If there are no air or vacuum leaks, you are going to want to rule out low fuel pressure. In addition, if you get one, you can make a couple of bucks smoke checking your friends and families Evaporative Emissions and intake systems when the time comes. It is a bit expensive, but i will save you a tone of time.
04 MAZDA 6 P0171 PRO
The smoke pro makes a pretty good product. However it works great for finding an air or a vacuum leak. A smoke machine is actually made to smoke the Evaporative Emissions system for leaks. If you suspect a small vacuum leak causing your p0171 lean code, you can use a smoke machine to smoke check the intake manifold to help find the leak.
04 MAZDA 6 P0171 CODE
Sometimes the intake manifold gasket, throttle body gasket or even a vacuum line or hose will leak engine vacuum which will result in a P0171 code in the computer. However, not all vacuum leaks are easy to find. This is a very important step! I cannot even begin to tell you how many air/vacuum leaks I have come across resulting in a p0171/p0174 lean code and or causing a major idle or performance problem! Most major vacuum leaks can be found by just by opening the hood and listening for a hissing sound while the engine is at idle as it will be very obvious. The first step in diagnosing a p0171 lean code is to check for air or vacuum leaks. Even if all of the sensors under the hood are good, if you have an air or a vacuum leak or if the fuel pressure is too low, then it will cause the engine to run lean and cause your p0171 lean code. If one of these sensors are off or “skewed”, the computer will run the engine either slightly rich or lean depending on how the sensor goes bad which will flag a P0172 Fuel Trim System Rich code (Bank 1). Ideally, you want it to run right in the middle. Based on this, the engine will run rich or lean. The cars computer determines injector pulse width based on the inputs it receives from various sensors. Depending on what type of vehicle you are working with will depend on what could be wrong which will therefore dictate how you are going to go about diagnosing this P0171 code. Just like a doctor to a sick patient, every case is different. Now, your next question should be, “how do I diagnose a P0171 lean code?” This my friend, is the 64 million dollar question. Toyota: Air/vacuum leak, oxygen sensor or mass air flow sensor. Note: the old Honda’s did not use a mass air flow sensor. Honda: Air/vacuum leak, oxygen sensor or Mass Air Flow Sensor. Most Dodge, Jeep and Chrysler vehicles do not use a Mass air flow sensor
![04 mazda 6 p0171 04 mazda 6 p0171](https://www.denlorstools.com/autoblog/wp-content/uploads/2009/06/Ford_Expedition_Hood_Up.jpg)
Sometimes a leaky fuel pressure regulator will cause this P0171 lean code too (depending on the fuel system of course).ĭodge Jeep and Chrysler: Air or vacuum leak or Oxygen Sensor. Most likely possible causes for this P0171 bank one lean condition per manufacture.įord, Lincoln and Mercury cars and trucks: Air or vacuum leak, Oxygen Sensor or Mass Air Flow Sensor.Ĭhevy or any GM vehicles: Air or vacuum leak or Mass Air Flow. If you have a lean code and would like some help, click here to chat with a mechanic online. If you have low fuel pressure, would the engine run lean? You bet it would! What if the engine had plugged fuel injectors or if one of the sensors on your engine was bad not allowing enough fuel into the engine while it was running? You guessed it! It would run lean and will definitely cause your P0171 diagnostic trouble code. If you have an air or a vacuum leak, would the engine run lean? Of course it would! The computer will see that the air fuel ratio is off and will light the check engine light and store the P0171 lean code that can be retrieved using a generic code reader or a scanner.
![04 mazda 6 p0171 04 mazda 6 p0171](https://ae01.alicdn.com/kf/HTB1az55LpXXXXaaXFXXq6xXFXXXe/New-Crankshaft-Position-Sensor-FN1221551-G4T08671-FN12-21-551A-For-04-12-For-Mazda-6-3.jpg)
![04 mazda 6 p0171 04 mazda 6 p0171](http://carphotos.cardomain.com/ride_images/3/2635/721/31585360001_large.jpg)
Well, let me ask you, what can cause an engine to run lean? This is the question I have to ask myself every time I diagnose one of these codes. As soon as the computer sees the air fuel ratio go too lean for a period of time two consecutive engine warm up cycles, it will flag your P0171 code. Not enough fuel for a given amount of air or too much air for a given amount of fuel. This code just simply means the engine is running “lean”. I hate to break it to you, but there is no “one” fix for this P0171 code. Everyone always asks me is “what is the fix for this P0171 lean code?” Everyone thinks there is one fix for all. I have have been dealing with this P0171 diagnostic trouble code for many years on many different year make and model vehicles. What does this code mean anyway? The definition for this this P0171 code is Fuel Trim System Lean (Bank 1).
![04 mazda 6 p0171 04 mazda 6 p0171](https://www.scannerdanner.com/media/kunena/attachments/5595/fuel_trims.png)
P0171 is a very common code for any ODB2 vehicle.