Error P0171 – how to fix?

Code definition P0171

System Too Poor (Bank 1)

What does the code P0171 mean

The OBD-II code P0171 indicates that the first engine bank fuel system is running low or there is a vacuum leak near that side of the engine. The lean state occurs when the engine receives too little fuel or too much air.

What are the causes of the P0171 code?

The reasons for the P0171 code may include:

• Defective fuel pressure regulator
• Poor fuel pump
• Clogged fuel filter
• Faulty powertrain control module
• Vacuum leak
• Damaged injector (s)
• Defective oxygen sensor (s)
• Damaged mass air sensor

What are the symptoms of the P0171 code?

Symptoms of the P0171 code may include:

• Loss of power
• Engine control lamp
• Engine wobbles or stalls
• The engine may be difficult to start
• The engine may die
• If this code is stored for a long time, the catalytic converter may be damaged.

How does the mechanic diagnose the P0171 code?

• Assuming there are no other fault codes, the mechanic can diagnose the P0171 code by checking the engine for vacuum leaks with a vacuum gauge. The vacuum leak causes a hissing noise that is usually only heard with the engine off.
• The fuel pressure sensor and MAF (mass air flow) sensor will also be checked with a pressure gauge.
• To maintain a proper air-to-fuel ratio, the engine vacuum and fuel pressure must meet the manufacturer’s specifications. The cause of the fault will likely be discovered during one of these two tests.
• If the mechanic still does not find the cause of the problem after performing these two tests, the problem is likely with the sensor.
• The mechanic will then test the mass air sensor and oxygen sensors in accordance with the manufacturer’s procedure.
• If all of these tests have been performed and no problems have been found, the problem is likely the powertrain control module.

The most common errors when diagnosing the code P0171

The error that occurs frequently does not look for any car model specific service bulletins that may be related to this issue.

While not all fault codes are associated with a service bulletin, it is always worth checking them out. They can save you a lot of time and effort.

How serious is the P0171 code?

The P0171 code is a serious problem. If a vehicle has this code stored in the powertrain control module, that vehicle’s engine simply will not run properly. If the engine does not maintain the proper air-fuel ratio, there will be a lot of fuel wasted and a lack of power while driving. It is a good idea to diagnose and repair this code as soon as possible to keep your vehicle running smoothly.

What repairs can fix the code P0171?

1. Replacing the fuel pump
2. Replacing the fuel filter
3. Replacing the fuel pressure regulator
4. Replace the powertrain control module
5. Replacing one or more injectors
6. Replace the oxygen sensor (s)
7. Replacing the mass air flow meter
8. Repair of vacuum leaks

Additional notes regarding code P0171

It is not recommended to drive the vehicle with a stored error code for a long time. If the engine malfunctions for an extended period of time, further damage can occur, which can prove significantly more costly to the vehicle owner.