P0170 OBD-II Trouble Code: Fuel Trim Malfunction (Bank 1)

Check Engine Light

P0170 code definition

Fuel Trim Malfunction (Bank 1)

What the P0170 code means

The P0170 code means that the powertrain control module is detecting a fuel trim that is outside the range of specification set by the vehicle’s manufacturer. This can mean a negative fuel trim or a positive fuel trim has been detected.

The powertrain control module receives a signal from the oxygen sensors and will adjust the amount of fuel the engine receives based on the readings provided by the oxygen sensors. This action carried out by the powertrain control module is called a fuel trim.

If the signal from the oxygen sensors calls for less fuel, the powertrain control module will act out a negative fuel trim. If the oxygen sensors call for a fuel increase, the powertrain control module will act out a positive fuel trim.

What are the causes of the P0170 code?

  • Any condition that causes the engine to run lean such as a weak fuel pump, a clogged fuel filter, or a faulty fuel pressure regulator

  • Any condition that causes the engine to run rich such as a mass air flow sensor, manifold absolute pressure sensor, or a faulty fuel pressure regulator

  • A faulty powertrain control module

What are the symptoms of the P0170 code?

Symptoms of this code may vary depending on the vehicle and other conditions that are present. Some symptoms that may occur include:

  • Decreased fuel mileage
  • Loss of power
  • Hesitation or stumbling from the engine
  • Check Engine Light
  • Catalytic converter damage (if this code exists for a long period of time)

How does a mechanic diagnose the P0170 code?

A mechanic may diagnose this trouble code by using an OBD-II scanner to make sure that no other codes exist. If any other codes are found, they may be causing this code to occur. If this is the case, the causes of any other code must be found and resolved first. This may include checking the engine for any issues that may cause it to run lean or rich and repairing them before moving forward.

After the repairs are made, the mechanic would reset the Check Engine Light and run the engine. If the Check Engine Light came back on with a P0170 code, then another problem exists. This problem is likely a powertrain control module if no other issues exist.

Common mistakes when diagnosing the P0170 code

Some people may look online and find that one of the most common causes of this code would be the mass air flow sensor. Once this information is found, the owner of the vehicle may decide to just replace the mass air flow sensor. It is always important to have engine issues diagnosed by a certified mechanic who follows the correct diagnostic procedures.

How serious is the P0170 code?

The P0170 code can range in seriousness. This code by itself causes no symptoms whatsoever, but in conjunction with other conditions, it may eventually lead to a large array of drivability issues. If this code exists for a long period of time in the powertrain control module, serious damage may result. If no symptoms are present while this code is stored, then the driver may be able to get by for a short period of time with this code saved.

What repairs can fix the P0170 code?

Additional comments regarding the P0170 code

The P0170 is one code that is important to have diagnosed as soon as possible. Once this issue has been diagnosed, the driver can decide how urgent the need for repair is. If no symptoms are associated with this code, then the driver may decide to hold off on the repair. If the driver experiences drivability issues they may decide to repair the vehicle sooner to avoid future problems.

Need help with a P0170 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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