What Codes Will This Page Cover?
- P0178 Fuel Composition Sensor Circuit Low Input
- P0179 Fuel Composition Sensor Circuit High Input
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What Is the P0178 Code?
Symptoms
Causes
Seriousness
Can I Still Drive?
Diagnose
Difficulty of Inspecting
Get Additional Help
These particular error codes indicate an issue with the circuit sensor attached to the system that monitors fuel quality and composition – in particular, this code commonly activates in cars that use flex fuels. The P0178 code indicates that the circuit is receiving low-voltage input or that there is an issue within the fuel composition (for example, if ethanol levels are above acceptable levels), while the P0179 code indicates that the circuit is receiving a high-voltage input. These show that the fuel composition is irregular or that the sensor is unable to properly and fully assess the fuel. When working properly, the sensor assesses the presence of non-gasoline (usually ethanol alcohol) when it is present in gasoline or E85 fuel at higher than 10%.
What Are the Symptoms of a P0178 Code?
If your car is experiencing the kinds of issues that prompt code P0178 or P0179 to show, then there are a range of symptoms you might see. The most obvious and immediate will be the activation of the check engine light, but this is a generic sign of trouble. More specific symptoms include:
- Lagging or stuttering acceleration
- Failure to start
- Rise in fuel consumption/ lower fuel efficiency
- Unexpected engine stalls
What Are Some Causes of a P0178 Code?
Whether your fuel composition sensor circuit is reporting low or high input, there are a number of likely causes and underlying issues that could be at work. These include, but are not limited to:
- Faulty or damaged fuel cap
- Contaminant in fuel
- Water in fuel
- Sensor defect or damage
- Restricted or damaged fuel line
- Faulty or damaged circuit wiring
- Faults in ECM
How Serious Is the P0178 Code?
P0178 and P0179 error codes are moderately serious and will certainly start to impact your cars drivability and safety after a short amount of time. How serious the issues become depends on precisely what the issues are. If there is water in the fuel, for example, your car may have trouble accelerating or maintaining its performance. This can make driving on highways and difficult roads unsafe.
Can I Still Drive with a P0178 Code?
It is possible to drive a car that is showing a P0178 or P0179 code for a short period of time, but it will become increasingly unsafe as the issues escalate. As such, you should have the problem assessed and addressed as quickly as possible to prevent health and safety issues.
How Easy Is It to Diagnose a P0178 Code?
Diagnosing the underlying causes of these codes should be straightforward for a professional, but there are some common mistakes that arise when diagnosing the cause of a P0178 or P0179 code:
- Disconnecting the sensor connector or replacing the sensor without checking if the wiring shorted or sustained damage.
- Mistaking misalignment or obstruction for damage or mechanical faults.
A thorough examination should uncover all contributing factors, however, as well as major areas of damage or wear and tear.
How Difficult Is It to Inspect a P0178 Code?
It can be very hard to physically inspect the components involved in the fuel composition analysis systems of a car because of their placement and delicate nature. A professional will be able to locate and inspect the fuel composition sensor and fuel line easily, however, and should be able to suggest an appropriate repair with ease.
Need Additional Help with Your P0178 Code?
The fuel composition sensor is one of the most important parts of the fuel injection system in a car and has a huge impact on a vehicle’s efficiency and drivability. If you see P0178 and P0179 codes flagged by your car, then it is best to deal with the issue quickly.
Expert, professional repairs are the most reliable and long-lasting. If you want to ensure that all secondary and tertiary issues are dealt with in full, then use the Kelley Blue Book repair shop locator to find a qualified car mechanic in your area. If your car is undrivable, then you can also filter to find shops that offer tow services!
If you want to know more about diagnostic codes and what they mean for your car, then the KBB OBD-II database is a comprehensive and reliable resource that breaks down the meanings, causes, symptoms, and severity of diagnostic codes. All you need to do is enter the code you observe and check whether its meaning is impacted by the type of car you have.
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