What is the P0173 fault number? What is Fuel Trim Failure (Bank 2)? How do you fix the P0173 fault code What are the causes and symptoms of the P0173 error code?
P0173 stands for “Fuel Trim Failure”. The code description states that “Bank 2” refers to the engine bank which does not contain the first cylinder. This fault code may be set for many reasons. A qualified mechanic should check for possible causes. The vehicle’s make and model may have different repair steps.
Meaning of P0173 Engine Failure Code
If the ratio of air-fuel mixture to fuel is too high or low, the ECU triggers fault code P0173. The ECU will compensate for vehicle’s rich or lean mixture in most cases. If the ECU’s compensation amount exceeds its set parameters, P0173 is displayed.
The ECU is responsible for adjusting the air-fuel mixture to meet changing engine conditions. For gasoline vehicles, the air fuel ratio should be close to 14.7 percent. For each unit of fuel, it takes 14.7 units air. This is the best mixture ratio to achieve the lowest emissions and most cost-effective fuel. This fuel mixture should be maintained even when the vehicle idles, drives downhill, or is driving at high speeds.
There are two types in air-fuel ratio settings. Both short-term and long-term… Short Term fuel trim (STFT), is nearly instantaneous. Long Term fuel trim (LTFT), is gradual tuning that occurs over longer periods.
What is the P0173 Fault code?
- – Mass Air Flow Sensor (MAF), Dirty or Defective
- – A leaky intake manifold, or a torn intake tube
- – Vacuum leaks
- – Defective fuel injector
- – Defective fuel pressure regulator
- Fuel filter and fuel line obstruction
- – Defective fuel pump
- – Oil contamination in O2 sensor connector
- – Defective O2 sensor
What are the symptoms for P0173 Fault Codes?
- – Illumination and operation of the engine fault lamps
- – Exhaust fumes or black smoke.
- – Sudden accelerations cause sudden power loss
- – Make a mistake while driving or idling
- – An increase in fuel consumption
How to Diagnose the Fault Code P0173?
- – You should check the Mass Air Flow sensor.
- – Measure the resistance and circuits of your Mass Air Flow Sensor with a multimeter.
- – A fuel pressure test should be performed.
- Check the wiring for damage in the fuel injectors.
- Check for leaks in the vacuum lines and intake manifold.
- – Short- and long-term testing should be done to determine if there are differences in the air-fuel mixture ratios.
Common Mistakes when diagnosing code P0173
- – Do not clean or test the Mass Air Flow sensor.
- – Recognizing that a component is defective, but not checking for more common causes like vacuum leaks.
- You should not use a scan tool to find out if there is an issue with the fuel trim.
- – Do not check the wiring of any component that is considered to be defective.
What is the importance of P0173 code?
- – Catalytic converters will experience a shorter life span as they will need to filter more fuel.
- Fuel consumption is on the rise.
NOTE: Some Mercedes-Benz models require that the crankcase breather tube located below the intake manifold be checked for cracks or leaks. Also, it is important to inspect the operation of hose’s check valve. The check valve should only be able to flow in one direction. Also, make sure to check the solenoids that adjust camshaft for leaks.
This fault code is common in European cars, especially Mercedes-Benz and Volkswagen. The possible cause could be a malfunctioning MAF sensor, or air flowmeter. This problem is rarer in Asian and American cars.
