7/9/2023 0 Comments P0171 chevy traxIn technical language this adjustment is called fuel trim. When there is too little oxygen in the exhaust (air/fuel mixture is rich), the PCM reduces the amount of fuel. This process is continuous: when the oxygen sensor detects too much oxygen, the PCM assumes that the air/fuel mixture is lean and adds more fuel. The PCM adjusts the fuel supply accordingly to keep the air/fuel ratio at the optimum level, which is 14.7/1 (14.7 parts of air to 1 part of fuel). The front oxygen sensor measures the amount of oxygen in the exhaust gases and provides the feedback signal to the engine computer (PCM) whether the air-fuel mixture coming into the engine is lean (too much air and too little fuel) or rich (too much fuel and too little air). Is a common reason for the code P0171 in many BMW vehicles. Some V6 Mazda vehicles (Tribute, MPV) also have this issue where the rubber elbow at the back of the intake manifold rips through, causing a vacuum leak and the code P0171. Another known issue in Ford vehicles is a vacuum leak from a ripped-through rubber elbow on one of the vacuum lines at the back of the intake manifold. Ford has issued a technical service bulletin on this issue. Many Ford vehicles, including Explorer and F150 had a common problem with leaking gaskets between the upper and lower intake manifolds causing the codes P0171 and P0174. If the leaking manifold gasket is confirmed following the diagnostic steps, it must be replaced. For example, the Toyota Technical Service Bulletin (TSB) EG045-07 for the 2003-08 Toyota Corolla and Matrix with the 1ZZ–FE engine mentions a leaking intake manifold gaskets in subfreezing temperature as a possible reason for the code P0171 along with some other codes. One way to find a common problem with your make and model is to search for technical service bulletins (TSBs). Here are a few examples of intake or vacuum leaks:Ĭommon problems causing the code P0171 in different cars: Read more: Vacuum leaks: common sources, symptoms, repairs. Common examples of vacuum leaks include a ripped or cracked intake boot, leaking intake manifold gaskets, stuck-open or defective PCV valve or ripped PCV hose, cracked or disconnected vacuum line. Read more about using a scan tool here.Īn air leak anywhere between the engine intake and the mass air flow sensor is often called a 'vacuum leak' or 'intake leak'. If the STFT is close to zero at idle, but elevates to 15-20% at higher rpms, the problem could be caused a faulty mass air flow sensor, clogged catalytic converter or low fuel pressure (bad fuel pump). If the STFT rises higher than plus 15-20% at idle, but drops at higher rpms, most likely you have a vacuum leak. Normally, both LTFT and STFT should be close to zero. If you have a scan tool, check Short Term Fuel Trim (STFT) and Long Term Fuel Trim (LTFT) readings at idle and at higher rpms (read more about fuel trims below). The best place to take your car for diagnostics is your local dealer - their technicians are factory-trained and know the common problems with the cars they service.īasic checks under the hood include: is the air filter box properly closed? Does the intake boot have any cracks? Are any of the vacuum lines or hoses disconnected? We have done some research and posted common problems for some cars, please read further. Without a scan tool, the only way to find the problem is to check the basics and research common problems with your particular car make, year and model. With a good scan tool that shows the live data diagnosing the code P0171 is fairly easy. Read more: Catalytic Converter: problems, replacement options. Improperly installed aftermarket intake Faulty PCV valve or other parts of PCV system Clogged or faulty Mass Air Flow sensor (MAF) Another symptom of an engine running lean is when there is an engine knock or detonation (pinging) under load or when accelerating uphill. The engine may also be difficult to start. If this code is caused by a vacuum leak, there might be a hissing noise coming from the engine. When an engine runs lean it lacks power and may stall when the car is stopped at a stop sign. The OBDII trouble code P0171 - System Too Lean (Bank 1) means that the engine air-fuel mixture is too lean, or there is too much air and too little fuel.ĭriving a car with the code P0171 can cause more damage to the engine over time, as when the engine runs lean, the combustion temperature is higher. Signs of automatic transmission problems.How to check the engine when buying a used car.How to get the best deal on a used car?.Buying a Used Car: 10 Common Mistakes to Avoid.
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