A proper air-fuel ratio is vital in ensuring excellent engine performance. Your car’s powertrain control module (PCM) is crucial in keeping this ratio in check. If the PCM cannot change the air-fuel ratio in your car due to car issues, it may activate the P0173 code. Will this diagnostic trouble code (DTC) severely affect your car?
The code indicates ‘Fuel Trim Malfunction (Bank 2)’ in the diagnostic trouble code (DTC) system. Numerous things can cause this, so a technician must identify the precise cause in your case to clear the code. This generic error code applies to any cars with OBD-II, particularly those manufactured since 1996.
Irrespective of the severity, you must diagnose and fix it as soon as the error code appears on your car’s dashboard. So, what are the causes and symptoms of the P0173 code? Know everything about this DTC!
What does the P0173 code mean?
The engine control module (ECM) activates the P0173 code when it determines that the air-fuel ratio is too low or excessively rich. The ECM can compensate for the lack of air or gas entering the engine in lean and rich conditions. However, the code activates if the compensation is excessive.
The code often indicates that the fuel trim mixture has become unusually lean (too much air; not enough fuel). But in some cases, it may also indicate that the mixture is excessively rich (too much fuel; not enough air) in certain cars.
There are mainly two types of air-fuel ratio adjustments: long-term and short-term. The short-term fuel trim happens suddenly. In contrast, long-term fuel trim is a progressive change that takes place over extended periods. Therefore, we recommend you stop driving if your car’s dashboard shows this code.
How serious is the P0173 code?
The code poses severe issues, so it is better that you don’t drive the car when the code activates. Two main things happen when the P0173 code activates.
- There will be a rise in gas consumption.
- The lifespan of your car’s catalytic converter will shorten as it will have to filter more contaminants from the exhaust fumes.
- It may cause damage to the PCM if it stays for a longer period.
Can I drive with a P0173 code?
It is better to stop driving your car when the code appears. Driving with this code will increase gas consumption and decrease the catalytic converter’s lifespan.
What causes a P0173 code?
The engine might run lean for various reasons, such as a blocked fuel filter, a weakened fuel pump, or poor fuel pressure. The same happens for rich situations caused by elements like a bad absolute pressure sensor, a faulty fuel pressure regulator, or a faulty airflow sensor. The below listed are a few factors that can activate this code.
- Damaged or dirty mass air flow sensor (MAF)
- Vacuum leakage
- A defective fuel injector or fuel pressure regulator
- Drained fuel line
- Engine oil gets saturated with fuel
- Leakage in turbo air charge hoses (if equipped)
- Unmetered air leakage
- Contamination with oil in the oxygen sensor or MAF connector
- Leaks in the ignition coils, the cam and crank sensors, or the oil sensors
- Camshaft adjuster solenoids that leak
What are the symptoms of the P0173 code?
The P0173 code’s symptoms can change depending on the car’s manufacturer. Additionally, other factors can affect the symptoms. However, these are the typical symptoms you can observe.
- Check Engine Light illuminates
- More smoke or dirt is coming from the exhaust
- The car suffers a loss in acceleration
- During idling, there will be hesitation or misfiring
- The fuel consumption increases
How does a mechanic diagnose code P0173?
A mechanic will perform the following steps to diagnose this DTC.
- They will have a visual inspection of the mass air flow sensor.
- Use a digital multimeter to check the mass air flow sensors and the circuit’s resistance.
- Then they will do a fuel pressure test.
- Next, they will check for fraying in the fuel injector wiring.
- Then the mechanic will search for leaks in the intake manifold and the vacuum lines.
- They will also use a scan tool to identify the out-of-range fuel trim, i.e., whether it is short-term or long-term.
Common mistakes that can happen when diagnosing the code
- They may replace the mass air flow sensor without first cleaning or testing it.
- Assuming a component is broken without looking for simpler explanations, including vacuum leaks.
- Not checking with a scan tool to see if there is a problem with the short-term or long-term fuel trim.
- Failing to check the wiring of the component, which may be at fault.
What repairs can fix the P0173 code?
You can do the following repairs when the code activates.
- Replacing the fuel pressure regulator, the mass air flow sensor, or the intake manifold gaskets.
- Fix a leaking brake booster. There may even be a need to replace or repair the engine air filter intake system.
- Replacing a defective fuel injector, a faulty fuel line, or a vacuum line attached to the throttle body.
Gerard Stevens is an experienced writer specializing in travel and car ownership in the U.S. With over five years in this field, he strives to simplify travel and driving for his readers. Gerard offers valuable guidance on various topics, including car and travel guides, helping his audience feel more confident in navigating these challenges.
