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Summary
  • Diagnostic trouble code (DTC) P2078 stands for “Intake Manifold Tuning (IMT) Valve Position Sensor/Switch Circuit High Bank 1.” It’s triggered when the powertrain control module (PCM) detects an implausible signal from the intake manifold tuning valve position sensor, which is in charge of providing the PCM with information about the tuning valve’s position.
  • Possible causes of the P2078 code include a faulty intake manifold tuning valve position sensor, circuit problems, a faulty intake manifold tuning valve, and a PCM that’s faulty or in need of a software update.
  • Symptoms of the P2078 code include an illuminated check engine light, reduced engine performance, poor fuel efficiency, and rough idle.

Some vehicles are equipped with an intake manifold tuning valve system that opens and closes one or more flaps in the intake manifold. The tuning valve allows more air to enter the engine when needed. When your engine’s intake manifold tuning valve or its sensors develops a problem, the P2078 code or other related trouble codes could trigger.

See also  P2004 Code: Intake Manifold Runner Control Solenoid Bank 1 – Solenoid Stuck Open

What Does the P2078 Code Mean?

Diagnostic trouble code (DTC) P2078 is defined as Intake Manifold Tuning (IMT) Valve Position Sensor/Switch Circuit High Bank 1. Your vehicle’s powertrain control module (PCM) will trigger the 2078 code when it detects an implausible signal from the intake manifold tuning valve position sensor. This sensor is responsible for giving the PCM information about the tuning valve’s position.

automotive intake manifold runner valve image
The PCM will trigger the 2078 code when it detects an implausible signal from the intake manifold tuning valve position sensor.

The intake manifold tuning valve is responsible for regulating the airflow inside the air passages that lead to the engine. Manipulating the amount of air that enters the engine helps it achieve better performance and efficiency.

Note: The definition of the P2078 code can differ depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of the P2078 Code?

The following issues commonly cause the P2078 code:

  • Faulty intake manifold tuning valve position sensor
  • Circuit problems, such as a damaged wire or poor connection
  • Faulty intake manifold tuning valve
  • Faulty PCM or software in need of an update
See also  P1518 Code: Intake Manifold Runner Control (Stuck Open)

What are the Common Symptoms of the P2078 Code?

Here are the common symptoms of the P2078 code:

low fuel light on
Another common symptom of the P2078 code is poor fuel efficiency.

How to Diagnose the P2078 Code

The P2078 code’s definition implies that the intake manifold tuning valves are faulty. While this might be the case, it’s possible that it isn’t the source of the problem. To fix this DTC, you must correctly identify the root cause. You’re probably going to need to do a visual inspection of and test the affected components and wiring, which can be quite challenging if you are unfamiliar with engines. You’re also probably going to need specialized tools and knowledge to do the said tests. If you are unfamiliar with DIY repairs, we recommend consulting a trusted mechanic to properly diagnose the problem.

Interested in diagnosing the P2078 code yourself? Check out the video below to learn more.

How to Fix the P2078 Code

The repair process for OBD-II trouble codes can vary significantly between vehicle models because they likely have different layouts and designs. As a result, there isn’t a single magic bullet fix that works for all DTCs. If you don’t have much experience troubleshooting DTCs, then we recommend leaving the task to a professional.

See also  P2016 Code: Intake Manifold Runner Position Sensor / Switch Circuit Low Bank 1

If you have the knowledge and skills for the task, then the first step to fixing the code is to properly diagnose its cause. After identifying the cause of the P2078 code, you can start consulting online repair resources and guides for possible fixes. Chilton repair manuals can be useful, but an ALLDATA DIY subscription might be better, as it provides factory repair information for other people interested in DIY repairs.

About The Authors
Written By Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Contact Center Manager and Technical Reviewer at CarParts.com

William “Bill” Guzenski has produced hundreds of how-to videos for the automotive community. He’s an ASE Certified Master Automobile Technician, and is affiliated with the Specialty Equipment Market Association (SEMA). He loves attending race events and car shows throughout the country, as well as traveling in his 40-foot motorhome, exploring abandoned mines and ghost towns.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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