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Summary
  • A logged P0079 code means that there’s an electrical problem with the exhaust valve control solenoid in bank 1, specifically a low voltage signal.
  • Circuit issues, a faulty control solenoid, and PCM problems can cause on-board diagnostics to set this code.
  • If this code is present, your vehicle will exhibit symptoms like an illuminated check engine light, increased fuel consumption, and decreased engine performance.

Code P0079 is an engine trouble code that involves your vehicle’s variable timing (VVT) system. It points to a potential issue related to the exhaust valve control solenoid circuit that’s located in Bank 1.

This trouble code is just one of many codes related to the intake valve and/or exhaust valve control solenoid. If your scan tool reads a P0079 code and you’re wondering what it means, here are a few things you should know.

What Does the P0079 Code Mean?

Diagnostic trouble code (DTC) P0079 stands for “Exhaust Valve Control Solenoid Circuit Low Bank 1.” This code is triggered once the vehicle’s powertrain control module (PCM) perceives that the voltage signal from the exhaust valve control solenoid circuit in Bank 1 is below the manufacturer-specified range. Bank 1 is the side of the engine that contains cylinder #1.

car mechanic checking P0079
If the PCM perceives that the voltage signal from the exhaust valve control solenoid circuit in Bank 1 is below the manufacturer-specified range, it may log code P0079.

P0079 on Some Hyundai Vehicles

The CVVT system built on the camshaft helps the engine decrease the exhaust gas and increase engine power and fuel economy by changing the valve open/close timing of the camshaft continuously. The valve control solenoid changes the direction of the oil path through the CVVT by the duty control of the PCM and changes the open and close timing of the intake and exhaust valves. 

See also  P0025 Code: Exhaust (B) Camshaft Position Timing Over-Retarded (Bank 2)

Code P0079 may appear on some Hyundai vehicles. On a 2012 Hyundai Elantra GLS 1.8L L4, for example, the PCM sets the code “if the PCM detects that the exhaust valve control solenoid control circuit is short to ground.”

P0079 code appearing in a 2012 Hyundai Elantra GLS 1.8L L4 can be caused by the following:

  • Short to ground in control circuit
  • Poor connection or damaged harness
  • Faulty Exhaust Valve Control Solenoid

Variable Valve Timing System

Many modern vehicles come equipped with a variable valve timing (VVT) system. This systematically regulates the opening and closing of the intake and/or exhaust valves to improve engine performance and increase fuel economy. A VVT system usually has actuator(s) that are situated at the end of the camshaft(s).

The PCM operates a control solenoid to apply oil pressure to each actuator, thereby adjusting valve timing. The PCM communicates with the control solenoid through a pulse width modulated (PWM) signal. Once the PCM detects a voltage signal that’s lower than the specified range, it will trigger the P0079 code.

Both intake and exhaust valves are crucial to the engine’s combustion process. The exhaust valve, for example, releases burnt gas from the cylinder after the combustion of the air-fuel mixture.

Make sure you understand what the control solenoid does before proceeding with any DIY repair for P0079.

Note: The definition of code P0079 may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

poor engine performance
One of the common symptoms of P0079 code is poor engine performance.

What are the Possible Causes of the P0079 Code?

  • Circuit issues
  • A faulty control solenoid
  • Malfunctioning PCM or software in need of an update
See also  P0023 Code: Exhaust “B” Camshaft Position Actuator Circuit (Bank 2)

What are the Common Symptoms of the P0079 Code?

check engine light on
An illuminated check engine light can also indicate P0079 code.

How to Diagnose the P0079 Code

It may be difficult to diagnose a P0079 code, especially if you’re not well-versed in auto repair. Without the right tools and know-how, it would be best to bring your vehicle to an auto shop and leave the job to a mechanic.

However, if you’re an experienced DIYer, you may consult vehicle-specific repair manuals to help you determine the exact diagnostic procedures that may work for your vehicle.

How to Fix the P0079 Code

Since the P0079 is typically set by circuit issues, diagnosing the problem will involve using a digital multimeter. You’ll need to check the voltage of the circuit between the PCM and the solenoid valve.

Diagnosing the Wiring Harness

To check for any shorts in the wiring harness, test the voltage using the multimeter’s positive lead on the car battery and the negative lead on each wire leading to the control solenoid. Unplug the harness connectors from the solenoid and PCM, then identify the + and – wires to the solenoid using a wiring diagram. Depending on the application, the solenoid may be controlled from the power side or the ground side. Factory wiring diagrams can be used to determine the direction of power flow in a circuit. Check for resistance between each end of the wire using a multimeter set to the ohms setting. A loose connection, an open circuit, or a faulty terminal could all cause an over-limit reading on the multimeter.

You should also check whether the connector and wiring harnesses are in proper condition. Check for any bent pins, moisture, or corrosion on the connector. If there’s any damaged wiring, then you should either repair or replace them.

Checking the Control Solenoid

Inspect for a short to ground through the control solenoid by putting a multimeter lead to a known good ground and the other lead to each terminal on the control solenoid. If there is resistance present, the solenoid may be shortened internally. Diagnosing this issue can be challenging if the issue goes away intermittently.  In extreme cases, it might be allowed to worsen before a correct diagnosis can be made.

See also  P0023 Code: Exhaust “B” Camshaft Position Actuator Circuit (Bank 2)

Where to Get a New Control Solenoid for Your Vehicle

Driving with a P0079 code could be costing you a lot of money. Not only does it decrease performance, but it can also increase fuel consumption. If faulty control solenoids triggered the code, don’t delay replacing them. Thankfully, here at CarParts.com, we have high-quality control solenoids on hand and ready to ship from a warehouse near you.

Our user-friendly website has everything you need to get your car back in shape. Take your pick from a wide selection of control solenoids sourced from the industry’s most trusted brands. All our products have passed strict quality checks, so you’re sure to get parts that are built to last.

Fill out our vehicle selector to filter the catalog to compatible parts for your car, SUV, or truck. You can also shop according to your preferred brand and price range using the search filters. If you need help with anything, feel free to contact our team via our toll-free hotline. We’re available round the clock to assist you.

Shop now, and take advantage of our unbeatable deals for control solenoids!

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 Technical Reviewer at CarParts.com

Richard McCuistian has worked for nearly 50 years in the automotive field as a professional technician, an instructor, and a freelance automotive writer for Motor Age, ACtion magazine, Power Stroke Registry, and others. Richard is ASE certified for more than 30 years in 10 categories, including L1 Advanced Engine Performance and Light Vehicle Diesel.

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.

File Under : OBD-II Trouble Codes Tagged With :
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