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P0170 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


Error Code P0170: Malfunction in Fuel Trim Bank 1


The generic error code P0170 appears when there is a significant problem and mechanical malfunction in your vehicle’s fuel trim in Bank 1. Your car’s Power Control Module (PCM) is responsible for maintaining your vehicle’s entire indoor and outdoor ecosystem. PCM receives direct signals from oxygen sensors highlighting the amount of fuel the engine requires. According to your engine’s fuel consumption rate, PCM adjusts the amount of fuel by undergoing a positive and negative fuel trim. 

When your car’s engine is working at its peak performance, the readings of oxygen sensors indicate that your engine requires more fuel, for which the PCM carries out a positive trim. However, oxygen sensors indicate a negative trim when excess fuel is pumped into your car’s engine. The car’s mainframe computer or the PCM is solely responsible for carrying out this process instantly and efficiently. The car’s PCM detects error code P0170 when an inconsistent fuel consumption rate does not comply with set ranges. The occurrence of error code P0170 directly indicates a problem in the air to fuel ratio and fuel trim controllers in the car’s mainframe computer. 


Many potential causes can be the reason for the occurrence of DTC error code P0170. Mechanical and electrical failures in your car’s engine can potentially cause a malfunction. Moreover, clogging in the fuel filter can create a physical barrier between the fuel pump and the generator. Furthermore, variable fuel pump pressure and frail fuel pump can also cause the error code P0170. To find the definite problem, one should thoroughly inspect every connection linking bank 1 sensors and the engine. Listed below are the few possible causes that might trigger the DTC error code P0170.

  • Leak or malfunction in turbo air change hoses
  • Malfunctioned injector
  • Saturated or contaminated engine oil
  • Clogging in air filter
  • Blockage in the air intake system 
  • Possible malfunction in the catalytic converter, muffler and exhaust pipe
  • Damaged coolant and airflow sensors
  • Frayed wiring and connections
  • Accumulated dust and carbon between connectors and fuses
  • PCM software issue


A severe malfunction of your engine’s fuel trim would impact your engine’s overall performance and fuel consumption. You might notice a slight decrease in your car’s mileage and fuel consumption ability. However, when the PCM detects the DTC error code P0170, there must be a definitive problem in your engine’s fuel trimmers. Mentioned below are possible symptoms one could experience and notice.

  • Illuminated check light on the dashboard
  • A significant drop in your car’s fuel mileage
  • Upon acceleration, the engine loses its efficiency and starts vibrating
  • Misfiring and suffocation in engine


As the PCM detects the DTC error code P0170, it is imperative to do a detailed inspection of your car’s engine room and Bank 1 sensors. To find the root cause of the error code P0170, one should inspect all connections, sensors and main engine units. If your car’s engine is misfiring and having issues in maintaining the air to fuel ratio, your car’s PCM would directly show the error code P0170. One can start their self-diagnosis by following the user manual or the user’s guide.

The self-diagnosis of the error code P0170 may include the following steps: 

  • Restart your vehicle and check whether the error code is reoccurring
  • Reset your PCM, and check for software updates
  • Check connectors, wirings, plugs and fuses
  • Inspect oxygen, airflow and coolant temperature sensors
  • Clean accumulated dust, carbon and soot in the connectors
  • Ensure the entire circuit is complete and functional

It is recommended to consult a professionally trained mechanic or an automobile technician who uses an OBD-II scanner to find out the root cause. The mechanic would freeze the PCM using the OBD-II scanner and deduce the main problem causing the DTC error code P0170. Moreover, the mechanic would start his preliminary analysis by visually inspecting the connectors, wirings, circuits, and integrated sensors in Bank 1.The automobile technician would start his analysis and follow the below-mentioned steps to evaluate the components causing the DTC error code P0170.

  • The automobile technician would use an OBD-II scanner to scan the PCM. After the initial scan, PCM would indicate the potential malfunctions causing the DTC error code P0170. 
  • The mechanic would also observe and check Mass Air Flow Sensors that might be damaged and need replacement. Moreover, after disconnecting the sensors, he would search for possible leaks in the regulator, causing variable fuel pressure.
  • Next, the mechanic would closely inspect all vacuum hoses and ensure no cracks or openings are causing air level fluctuations.
  • The mechanic would also check all connections, wirings, and fuses in the primary circuit. Moreover, he would review oil levels and terminal circuits to ensure they comply with the brand’s specifications.

Common mistakes

While diagnosing the cause of DTC error code P0170, one shouldn’t replace airflow or oxygen sensors without consultation. At times, users search for online solutions and immediately take action by replacing the sensors in Bank 1. However, you must always consult a professional mechanic who would conduct a detailed inspection of your car’s engine and search for specific problems causing the error code P0170. Before any replacement, one should always clean the contaminated dust, carbon and impurities on sensors and other connected components.

How serious is this?

When your car’s PCM detects the error code P0170, you must resolve it on a priority basis. The reoccurring error code P0170 can impact your engine’s health and affect its overall functioning and efficiency. Moreover, this would impact your car’s mileage and cause problems during ignition and acceleration. If the error code P0170 isn’t repaired, it would cause severe problems in the short term and affect your vehicle’s drivability.

What repairs can fix the code?

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To resolve the DTC error code P0170, it is crucial to check all Bank 1 components and sensors likely to malfunction and get damaged. Replacing fuses, connectors, and vacuum pumps might solve the problem in the short term. However, it is advisable to consult a qualified motor technician.

Related codes


Every driver aspires to enjoy a hassle-free drive, which is only possible if you regularly maintain your vehicle and check for significant repairs. To avoid DTC error code P0170, it is imperative to check your engine’s oxygen sensors which are responsible for balancing the fuel trim. To improve your vehicle’s mileage and fuel consumption, it is vital to check and clean oxygen and airflow sensors regularly.

P0170 Code – What Does It Mean & How To Fix It