P0171 System Too Lean Bank 1

Technical description of error P0171

The system is too poor (bank 1)

What does code P0171 mean?

This Diagnostic Trouble Code (DTC) is a generic transmission code. It is considered universal as it applies to all makes and models of cars (1996 and newer), although the specific repair steps may differ slightly depending on the model. So this article with engine codes applies to Toyota, Chevrolet, Ford, Nissan, Honda, GMC, Dodge, etc.

This basically means that the oxygen sensor in bank 1 has detected a lean mixture (too much oxygen in the exhaust). On V6/V8/V10 engines, bank 1 is the side of the engine that cylinder #1 is installed on. P0171 is one of the most common trouble codes.

This code is triggered by the first bottom (front) O2 sensor. The sensor provides a reading of the air: fuel ratio exiting the engine cylinders, and the vehicle's powertrain / engine control module (PCM / ECM) uses this reading and adjusts so that the engine is running at an optimal ratio of 14.7: 1. If something is wrong, the PCM can't keep 14.7: 1 ratio but too much air, it runs this code.

You will also want to read our article on short and long term fuel trim to understand engine performance. Note. This DTC is very similar to P0174, and in fact, your car may display both codes at the same time.

Symptoms of error P0171

You most likely will not notice any problems with the car's handling, although there may be symptoms such as:

• lack of power
• detonation (spark detonation)
• rough idle
• fluctuations / bursts during acceleration.

Causes of the P0171 code

The P0171 code may mean that one or more of the following events have occurred:

• Mass air flow (MAF) sensor is dirty or defective. Note. Using "oiled" air filters can contaminate the MAF sensor if the filter is overly lubricated. There is also a problem with some vehicles in which the MAF sensors leak the silicone sealing material used to protect the circuit.
• Possible vacuum leak downstream of the MAF sensor.
• Possible crack in vacuum or PCV line / connection
• Faulty or stuck open PCV valve
• Defective or faulty oxygen sensor (bank 1, sensor 1)
• Stuck / clogged or failed fuel injector
• Low fuel pressure (possibly clogged / dirty fuel filter!)
• Exhaust gas leak between engine and first oxygen sensor

Possible solutions

Frequently cleaning the MAF sensor and detecting / repairing vacuum leaks will fix the problem. If you're on a tight budget, start with this, but it might not be the best solution. So, possible solutions include:

• Clean the MAF sensor. If you need help, refer to the service manual for its location. I find it best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor and make sure it is dry before reinstalling.
• Inspect all vacuum and PCV hoses and replace / repair as needed.
• Inspect all hoses and connections in the air intake system.
• Inspect and / or check the intake manifold gaskets for leaks.
• Check if the fuel filter is dirty and if the fuel pressure is correct.
• Ideally, you will want to track short and long term fuel trims with an advanced diagnostic tool.
• If you have access, you can run a smoke test.

Repair Tips

The following practices may in some cases be effective in diagnosing and resolving the problem:

• Cleaning the Mass Air Flow Sensor
• Check and, if necessary, repair and replace the intake pipes and the PCV valve (forced crankcase ventilation).
• Checking the connecting pipes of the air intake system
• Inspection of intake manifold gaskets for tightness
• Checking the fuel filter, which, if dirty, must be replaced or cleaned
• Fuel pressure check

As you can see, it includes a number of checks and interventions that, with a little experience, you can carry out on your own.

If you leave your car in the hands of a mechanic, they can diagnose the P0171 trouble code by checking fuel pressure with a gauge and for vacuum leaks with a vacuum gauge. In the event that both of these tests fail, then the problem should be sought in the oxygen sensors, which should be checked in accordance with the recommendations of the car manufacturer.

It should also be borne in mind that long-term storage of the p0171 error code can lead to catalytic converter failure. The p0171 error code is actually generally associated with a rather serious problem, which can also cause a general engine malfunction, since the engine will not work due to a changed air / fuel ratio, despite the possibility of driving the car. efficient, also requiring higher fuel consumption. For this reason, as soon as this error code appears on your dashboard, it is advisable to fix the problem right away. Circulation with this code, although possible, is not recommended.

As for DTC p0171, the cost of repairs, including parts and labor, can be roughly calculated as follows.

• suction pipe replacement: 10 – 50 euros
• Oxygen sensor replacement: 200 – 300 euros
• Replacing the PCV valve: 20 - 60 euros

To these amounts should be added the costs of diagnostics, which can vary from workshop to workshop.

Frequently Asked Questions (FAQ)

What does code P0171 mean?

DTC P0171 signals a too lean fuel mixture, which is due to the presence of too much air.

What causes the P0171 code?

There are several reasons for the appearance of the P0171 DTC: failure of the oxygen sensor; fuel sensor failure; malfunction of the air flow sensor; open or defective PCV valve, etc.

How to fix code P0171?

Systematically check the functionality of all parts that may be associated with a P0171 DTC as noted above.

Can code P0171 go away on its own?

Unfortunately no. The code P0171 cannot go away on its own and will require the intervention of a qualified mechanic.

Can I drive with code P0171?

Circulation with this code, although possible, is not recommended.

How much does it cost to fix code P0171?

Here are the estimated costs to resolve DTC P0171:

• suction pipe replacement: 10 – 50 euros
• Oxygen sensor replacement: 200 – 300 euros
• Replacing the PCV valve: 20 - 60 euros

To these amounts should be added the costs of diagnostics, which can vary from workshop to workshop.

How to Fix P0171 Engine Code in 2 Minutes [2 DIY Methods / Only $8.37]

Need more help with your p0171 code?

If you still need help with DTC P0171, post a question in the comments below this article.

NOTE. This information is provided for informational purposes only. It is not intended to be used as a repair recommendation and we are not responsible for any action you take on any vehicle. All information on this site is protected by copyright.