How to Fix Code P0170: Understand the Causes and Find the Solution

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Cellphone with code P0170 on display

Do you have a Check Engine Light on in your car? If so, there is a good chance that the code P0170 has been triggered. The code means that the engine airflow sensor has trouble reading the incoming data. How does this happen, and how can it be fixed? Read on to find out more!

What is Code P0170?

P0170 stands for "Fuel Trim Malfunction (Bank 1)." Fuel trim is the adjustment caused by the PCM to the engine's air-fuel mixture. It indicates how close your car's fuel tank is to run out and has reached an abnormally low or high value for a specified amount of time. The fault light in the dashboard will come on if you are below 1/4 tank, and it also beeps when this happens.

Causes of Code P0170

There could be multiple issues with your car triggering the code P0170. If the error code shows "Fuel Trim Malfunction (Bank 1)," then the lists below are the possible causes triggering the code.

  • Lack of fuel
  • Intake air leaks
  • Faulty front heated oxygen sensor
  • Ignition misfiring
  • Faulty fuel injectors

Common Signs of Code P0170

If your car has a P0170 code, you may notice some of these issues:

  • Engine misfires or shakes when you try to start it up.
  • The check engine light comes on and doesn't go away even after a few starts.
  • Your car is not getting as much power as usual, so your gas mileage will be lower than normal.
  • The engine stalls or has a rough idle.

How to Fix Code P0170?

1. Lack of Fuel

Lack of fuel is the number one reason for code P0170. There are a few things you can do to try and fix this:

  • Check the fuel pump - make sure it's getting power and is functioning correctly.
  • Change the fuel filter.
  • Add more fuel additives to your tank.

If you've done trying all of these steps and still can't seem to check to see if the gas cap is loose and make sure the tank is full. If it's not either of those things, you might have to take your car in for a tune-up.

2. Intake Air Leaks

Suppose the air leaks and has not had enough fresh air to enter your car's engine, resulting in a lean mixture. The oxygen sensor will detect how much fuel is needed, which might be more than what is being provided by the engine or less. 

To fix this issue, do the following steps:

  • Identify the leak.
  • After finding it, use a sealant or duct tape to fix the hole.
  • If the leak is big or too many leaks to fix, you might need to buy an aftermarket intake system.
  • Replace air filters if necessary.
  • Check the MAF sensor and make sure it's not dirty.
  • Clean throttle body and IAC valve.

If these things don't work, you might need to buy a new oxygen sensor.

3. Faulty Front Heated Oxygen Sensor

This is another common problem that drivers often come across. This sensor is crucial in measuring how much oxygen should be provided to the engine, resulting in how well your car performs. There are the causes of faulty front heated oxygen sensor:

  • The oxygen sensor fuse may have blown.
  • The fuel pressure may be too high or too low.
  • There is maybe a vacuum leak in the engine.

To fix this issue, do the following steps:

  • Try to see if leaves or other debris are stuck on the front heated oxygen sensor and clean it immediately.
  • Check if the wires are correctly connected.
  • If it's still not working, your sensor might be faulty, and you will have to replace this part with a new one.

Replace Oxygen Sensor

Suppose the simple steps above did not work for you, then replacing your oxygen sensor is your last resort. Do the steps below to replace your faulty oxygen sensor.

  • Unclip the electrical connection so you can get the socket on.
  • When the socket goes on, pull it on.
  • When it's loose, unscrew it with your bare hands.
  • After successfully removing it from your vehicle, install a new oxygen sensor using a torque wrench and socket.

Note: Always replace it with the same brand.

4. Ignition Misfiring

If a faulty oxygen sensor causes your ignition misfiring, the code P0170 will be stored in your car's computer. We recommend trying the simplest solution first and then progressing to more complex solutions if that does not work.

The most common cause of ignition misfire is a dirty or faulty sparkplug. This means your sparkplugs are possibly mishandled and installed improperly. This could also be because of malfunctioning ignition coils, carbon tracking, defective spark plug wires, and vacuum leaks.

Replace the Sparkplug

Before replacing your sparkplug, make sure to check it first if a remedy will work or it is a candidate for replacing. If you found out that it's for a replacement already, below are the steps on how to do it:

  • Locate the sparkplug wire. It's usually located near the distributor cap.
  • Remove the engine cover and disconnect the sparkplug wires from each of your plugs.
  • Remove the sparkplug wire by unscrewing it. You can use a socket wrench for this.
  • Install the new plug by screwing it in place and connecting the appropriate wire. Make sure that you don't overtighten it, or else you might strip the threads on the plug.

5. Faulty Fuel Injectors

If the faulty fuel injector is causing you the code P0170, you will need to replace it. You might not be familiar with how exactly how to do this or how much it would cost. But that doesn't mean that there are no ways to fix the problem independently. 

One of the common causes for a faulty fuel injector is that it has become dirty or clogged. Over time, deposits can form on the injectors and cause them to get clogged. 

To fix this issue, do the following steps:

Clean the Injectors

If you find out that it is just clogged and doesn't need a replacement, you can clean it with a carburetor cleaner. If the injector is dirty, this will help dissolve the dirt and hopefully clear up your code P0170.

Replace the Fuel Injector

If you've tried cleaning it, but that hasn't worked, then the next step would be to replace the fuel injector altogether. A professional should do this for you, or if you're feeling adventurous, you could try to do it yourself. 

Just make sure you have the right tools and knowledge before attempting this! If you are confident enough to do it yourself, try these steps:

  • Unplug all the fuel injector connectors.
  • Using a wrench, loosen up each bolt on the fuel rail. You don't need to remove them all the way, just enough so you can slide the fuel rail off of the engine.
  • Once the fuel rail is loose, gently pull it up and away from the engine. This will expose the fuel injectors.
  • Replace the fuel injector with a new one, and tighten up the bolts.
  • Reconnect everything how it was before you started - push down on the rail to align all of the holes and then slide it back into place.

Warning: Make sure the new injector has new seals. Never use the old seals over.

P0170 Code FAQ

1. What causes fuel trim problems?

Changes in the oxygen levels of exhaust gases cause short-term fuel trim. The flow is monitored by an oxygen sensor, which gives a signal proportional to the oxygen levels in the gases. The ECU will react promptly when the exhaust gases change in a fully operating system.

2. Can I drive having the P0170 Code?

Yes. You can still drive the car with this code. You may see some fuel mileage loss when driving with this code, but the vehicle should get you to your destination.

3. What are the possible causes of positive Fuel Trim at idle?

When the throttle plate is closed, the intake manifold vacuum is high, and only a tiny amount of un-metered air enters the engine, so even a tiny amount of un-metered air will affect fuel trim. This forces the PCM to react with positive valued fuel trim readings to the lean condition.

4. What sensors affect fuel trim?

As the incoming air temperature varies, the signal from the Intake Air Temperature sensor changes. The thinner the air is, the warmer it is. The oxygen sensors keep track of how well the computer's fuel-trim approach works. The sensor is positioned in the exhaust and measures the amount of oxygen that has not been burned.

5. Can a clogged air filter harm my diesel engine?

A clogged diesel air filter can compromise the engine's power output. The clogged filters make it harder for engines to draw in air and choke up your machine. It can drain the power out of your engine if it happens, resulting in power loss.


Fixing the P0170 code error is not an easy thing to do, so If you are not an expert on fixing code P0170, you will need to take your car to a mechanic. However, there are various ways to fix code P0170 on your own, but if these ways do not work, you will need to take it in for repair. 

We hope this blog post has helped you understand the code P0170 and what you should do if it pops up on your OBDII scanner.