Diagnostic Trouble Code P0170

P0170 “Fuel Trim (Bank 1)”


What is code P0170?

Code P0170 stands for “Fuel Trim (Bank 1)”. This diagnostic trouble code can happen for a number of reasons related to how much fuel enters the combustion chambers, whether too much or too little. Therefore, it is important to have a qualified technician diagnose the specific problem that caused the code to be stored in your vehicle’s computer.

Get this checked out soon by a CarAdvise shop, where the work will be guaranteed, and one of our expert techs will review any repair orders.

What does code P0170 mean?

If code P0170 shows up during a diagnostic scan of your vehicle, a technician understands that there is something wrong with the fuel trim, the adjustment by the ECM (engine control module) to the ratio of air to fuel that makes its way into an engine

In order for your engine to function properly, it requires a specific air to fuel ratio that enters the combustion chambers. The ratio of air to fuel is also important to maximize engine performance, minimize emissions, and avoid damage to the engine or other components.

If the air/fuel ratio is out of balance, the result could be too much fuel (or not enough air), what is referred to as a “rich” operating condition. In that case, excess amounts of unburned fuel escape through the exhaust. Your engine loses fuel economy and emits more pollutants. On the other hand, the result could be too little fuel (or too much air) leading to a “lean” operating condition that can also cause problems with fuel efficiency, pollution, and even internal engine damage.

Code P0170 is the general code for when the ECM (or PCM, Powertrain Control Module) detects that the fuel trim is outside of a specified range. When this happens, code P0170 is thrown and the check engine lights up.


What causes code P0170?

A number of causes can trigger a code P0170. That is why an accurate diagnosis is essential. Causes of this code include anything that makes the engine run rich or lean. For instance:

Most likely

Other possibilities


What symptoms are associated with this code?

Common signs associated with a code P0170 include the following:

  • The check engine light is on or flashing
  • Reduced fuel economy due to excess fuel consumption
  • Failed emissions test
  • Engine shakes, runs roughly, or lacks power
  • Engine stalling or difficult to start
  • Engine sputters or hesitates on acceleration
  • Catalytic converter overheating and damage


How does a technician diagnose code P0170?

If a diagnostic scan of your vehicle indicates a code P0170, a technician will perform tests to pinpoint the problem. These tests include checking for any related trouble codes. The technician will also use the scan tool to read the live data of multiple values related to combustion that could directly affect how the engine runs. These include fuel pressure, injector pulse width, and mass air flow data. The technician might also inject additional fuel into the engine while it is running and observe oxygen sensor feedback data on the diagnostic scan tool. The fuel and intake system will also be visually inspected to look for common problems such as a clogged air filter, dirty mass air flow sensor, or leaking fuel pressure regulator. A temperature gun might also be used to monitor the temperature of the catalytic converter to determine if it is plugged.


How serious is this code?

You might not always notice a difference in how your vehicle runs with a code P0170, but it is not a good idea to drive for very long with this code present. Both a “rich” and “lean” operating condition can lead to a drop in fuel economy and increased engine emissions. More than that, if your engine is running too rich or lean, damage can occur to your engine or other components eventually. Code P0170 is not a cause for immediate concern, but should be addressed as soon as reasonably possible.

Get this checked out soon by a CarAdvise shop, where the work will be guaranteed, and one of our expert techs will review any repair orders.


Related Diagnostic Trouble Codes

P0172 “System Too Rich (Bank 1)”

P0174 “System Too Lean (Bank 2)” 

P0175 ” System Too Rich (Bank 2)”


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