If the engine is run with the P0171 trouble code, it may result in engine performance being affected. These are trouble codes triggered by the vehicle’s ECU, indicating an incorrect ratio of the air-to-fuel mixture in the engine.
You will read about the P0171 trouble code in detail in this article. Including meaning, causes, symptoms, and how to fix the P0171 fault.
P0171 Code Definition
P0171 Definition is : System Too Lean (Bank1)
What Does The P0171 Code Mean?
The P0171 code in any modern vehicle indicates a “System to Lean (Bank 1)” condition in the engine, which indicates the engine is receiving more air and less fuel than the optimal air-fuel mixture.
Code P0171 The ratio of air and fuel entering the vehicle’s engine combustion chamber is incorrect. Because the fuel mixture is set to 14.7:1 as per the correct firing sequence of the engine, But when there is a difference in the ratio of this prescribed ratio, Then the P0171 code may occur.
If there is a higher ratio of air to fuel in the combustion chamber of the engine, this will result in a lower fuel-to-air ratio for the fuel mixture to burn.
Also, a faulty fuel pump or fuel injector can cause an imbalance in the fuel mixture ratio. Due to this, the ratio of air to fuel in the engine’s fuel mixture may increase or decrease.
Problems with the fuel assembly can also result in damage to other components, such as the fuel filter or fuel pipeline. Some DI and CRDI engines may also have a P0171 code due to a faulty fuel common rail or DRV valve switch.
What Causes Of A P0171 code?
Common causes of the P0171 code (System Too Lean Bank1) can include a vacuum leak in the intake system, a faulty mass airflow sensor, clogged fuel injectors, or a bad oxygen sensor.
Let us go through these reasons in detail, one by one, so that you can do the proper investigation and solution when the P0171 code is displayed.
1. Vacuum Leakage
The P0171 code can also appear if there is an air vacuum leak somewhere in the engine’s vacuum assembly line. Leaking throttle body gaskets can be one of the main causes of vacuum leaks. It may be necessary to check for leaks in the throttle gasket when this code appears.
2. Weak Fuel Pump
The fuel pump delivers fuel to the injector with high pressure, causing the fuel injector to spray fuel into the combustion chamber.
But if the fuel pump is sending fuel to the injectors with low pressure, the P0171 code may still appear. To eliminate this problem, check the fuel pump and repair or replace it if it malfunctions.
3. Faulty Fuel Injectors
Fuel injectors play an important role in the smooth running of the vehicle’s engine because they spray fuel on the engine’s piston, and the spraying ratio of the fuel injectors is determined by the company.
But due to some kind of fault in the fuel injector, the fuel spray ratio becomes faulty, due to which the fuel injector starts spraying less or more of the fuel, or when the fuel injector gets clogged, the fuel starts leaking.
This may also cause the P0171 code to appear. For this, get the fuel injector cleaned or replaced.
4. Clogged Catalytic Converter
The catalytic converter expels up to 90% of the toxic and polluting gases from the engine through the exhaust pipe. But sometimes the catalytic converter gets clogged due to excess carbon in the smoke coming out of the engine.
Due to this, the hot gases coming out of the combustion chamber of the engine are not exhausted properly. This may also cause the P0171 code to appear.
5. Faulty Fuel Pressure Regulator
The fuel pressure regulator is installed in the engine of vehicles to send fuel under pressure, which manages the fuel supply at the prescribed pressure.
But sometimes this fuel pressure regulator gets damaged or breaks, due to which the fuel becomes unable to manage the pressure. Due to this, the ratio of the fuel mixture can also get disturbed and the chances of seeing code P0171.
6. Clogged Fuel Filter
A fuel filter is installed in the fuel assembly to allow the fuel supply to flow cleanly to the injectors or fuel pump in vehicles.
But sometimes not changing the old fuel filter for a long time can also cause the filter to become clogged and the fuel supply disrupted, due to which the fuel does not reach the injector or fuel pump completely and the fuel gets mixed with the fuel mixture. The quantity may be less.
7. Faulty ECU Unit
The ECU unit is also called the brain of any vehicle. which controls all the active movements of the vehicle with proper timing.
But sometimes, for some reason, there is some kind of error or malfunction in the ECU unit of the vehicle or the components inside the ECU get damaged.
Due to this, the ECU may be unable to operate all the functions properly. A bad ECU can make a difference in the ratio of this fuel mixture, which can lead to P0171.
8. Faulty Oxygen Sensor
The oxygen sensor sends a signal to the ECU module to know the ratio of oxygen in the exhaust gases coming out of the vehicle’s engine combustion chamber.
Based on which the ECU prepares the fuel firing order with proper timing and sends according to the position of the piston with proper timing.
If there is any defect in the oxygen sensor, then this sensor becomes unable to sense the amount of oxygen in the gases coming out of the manifold and is not able to send a signal to the ECU.
9. Faulty Airflow Mass Sensor
This sensor may be installed in the vehicle’s air filter pipe or in the air filter box itself, which senses the ratio of pure air mixed with fuel by the vacuum and sends a signal to the ECU. Based on which the ECU prepares the right fuel mixture with the right timing.
But sometimes, due to some reason, this airflow mass sensor can get damaged, which would prevent it from sending the output signal correctly. For this reason, the P0171 error code may also appear.
Symptoms Of A P0171 Fault Code
Common symptoms of the P0171 fault code may include check engine light, poor fuel economy, rough idle, hesitation in acceleration, or increased exhaust emissions, which can reduce engine performance and increase emissions.
1. Check Engine Light
In the event of a malfunction of any sensor related to the engine of the vehicle, the warning light in the cluster meter of the vehicle may turn on.
If error code P0171 occurs in the engine of the vehicle, So the check engine warning light in the cluster meter may be on, which shows P0171 when the vehicle is scanned by a digital scanner. These symptoms could also indicate an error in code P0171.
2. Engine Rough Idle Position
If the engine is by starting it at idle, the needle on the engine’s rpm meter may be sub-down, and the engine can do hunting (up and down) when started in the idle position. RPM up or down when the vehicle engine is started in the idle position can also result in an error code of P0171.
3. Engine Misfire
If you press the accelerator to increase the speed of a moving vehicle, Then the engine of the vehicle may misfire in this situation. And the vehicle will be moving while shaking. These symptoms can also be a main symptom of getting the P0171 code.
4. Loss Engine Power
If the code P0171 is encountered, the vehicle’s engine performance and power may decrease because the combustion process in the engine is interrupted.
Which causes the RPM to decrease when the vehicle is gaining speed or applying thrust. These symptoms can also be associated with code P0171.
However, there can be many other reasons for the power and performance of the vehicle. For which such symptoms may be required to get the vehicle diagnosed from an expert mechanic of the vehicle.
How to Fix the P0171 Code
Fixing the P0171 code may require an expert vehicle mechanic. For this, the vehicle will have to be scanned with a digital scanner. So that it can be easily known what the main reason for code P0171 is.
First, scan the vehicle system with the OBD scanner and check the root cause of P0171 once all the fault codes are cleared by the scanner. After this, take a test drive of the vehicle.
If the Check Engine or any other warning light displays again after some time, you will need to have a mechanic investigate and resolve the root cause of the problem. For this, follow the process mentioned below.
- Check the MAF Sensor: Often the main cause of code P0171 in vehicles is the mass airflow sensor, which can be cleaned and reinstalled. But if the mass airflow sensor is bad, replace it with a new one.
- Check and Repair Vacuum Leaks: Vacuum leaks in the vehicle can also be a major cause of the P0171 code. For this, check the entire vacuum assembly for leakage. Typically, this could be a vacuum leak from the throttle body gasket or pipe, or the throttle body could be broken. For this, replace the throttle body with a new one or change the gasket. Check all the pipes connected to the vacuum, and if there is vacuum leakage, replace the new pipe and tighten it with a clamp.
- Check Oxygen Sensor: Code P0171 can occur if a vehicle’s oxygen sensor is broken or the wire is broken. For this, replace the other oxygen sensor. And after that, reset all trouble codes by scanner.
- Clean the fuel injectors: Sometimes fuel injectors become clogged or damaged due to prolonged use. For this, first clean the fuel injector with a high-pressure machine. And if the fuel injector is bad, then replace it with a new one.
- Check the Fuel Filter and Pump: A clogged fuel filter or a weak fuel pump can be the main cause of getting the P0171 code. For this, check them first. If the fuel filter becomes clogged, replace it again. And if the fuel pump is weak, get it repaired or replaced with a new one.
- Check and replace the fuel pressure regulator: The fuel pressure regulator manages the fuel pressure for the vehicle’s engine. But sometimes the fuel pressure regulator valve malfunctions, due to which the fuel pressure starts decreasing. Due to which code P0171 can come. For this, the fuel pressure regulator needs to be replaced with a new one.
- Clear Fault Codes: Once you’ve fixed the root problem of the P0171 code, clear all fault codes from the vehicle’s system with an OBD scanner and take a test drive. Hopefully, now you have gotten rid of this P0171 code problem.
System Too Lean Bank 1 Repair Cost
Typically, the mechanic’s labor to diagnose and repair this P0171 fault code can range from $80 to $180. If you have a faulty fuel pump, you can also expect to pay over $200 for a new unit and the fuel injector costs $50.
The cost of fixing the P0171 code depends on the model of the vehicle and the defective parts, as well as the diligence of the mechanic.
Q. P0171 Code Ford
For Ford, this code, P0171, means either too much oxygen or not enough fuel when System Too Lean Bank 1 is present. This is a low fuel trim code, or “lean” condition.
The P0171 OBD-II code indicates a bad fuel system on the first side of the engine or a vacuum leak on this side of the engine. These vacuum leaks can happen for a number of reasons, which weakens the fuel mixture and due to which the combustion process in the engine is interrupted.
Q. P0171 Code Chevy
In Chevy, this code P0171 means there is either too much oxygen or not enough fuel when the system is too lean and bank 1 is present.
This is a low fuel trim code or “lean” condition. The P0171 OBD-II code indicates a bad fuel system on the first side of the engine or a vacuum leak on this side of the engine.
These vacuum leaks can happen for a number of reasons, which weaken the fuel mixture. And due to this, the combustion process in the engine is interrupted. The P0171 code indicates an error in the ratio of air to fuel in the engine’s fuel ratio.
Q. Is It Ok To Drive With P0171 Code?
P0171 refers to a disturbance in the ratio of fuel to air consumed in the engine of a vehicle. Due to this, the engine may overheat. Engine power and performance may decrease due to this code. Also, fuel mileage may drop. Due to this, the engine will consume more fuel.
Banty is the owner of Autorepairszone.com & is also a vehicle mechanic by profession. We have almost 12 years of experience in the field of automotive repair, and we strive to provide you with accurate information about vehicle malfunctions and repairs based on our experience.