P0079 — Exhaust Valve Control Solenoid Bank 1 – Circuit Low #

Note: The code description may vary depending on the manufacturer. Always refer to your OEM repair manual for model-specific terminology.

• Exhaust Valve Control Solenoid Circuit Low (General)
• Exhaust Valve Control Solenoid ‘A’ Circuit Low (Ford, GM, Honda, Toyota)
• Variable Valve Timing (VVT) Exhaust Control Solenoid Circuit Low (Hyundai/Kia)
• Exhaust Camshaft Timing Control Solenoid Circuit Low (Nissan/Infiniti)

Summary of DTC P0079 #

The P0079 diagnostic trouble code (DTC) indicates that the Engine Control Module (ECM) has detected a low electrical condition in the exhaust valve control solenoid circuit for Bank 1 (the side of the engine containing cylinder 1). This solenoid is a key component of Variable Valve Timing (VVT) or Variable Camshaft Timing (VCT) systems, which adjust exhaust valve timing for optimal performance and emissions. A “circuit low” condition means the voltage or current is below the expected threshold, often due to electrical or component failure. If left unaddressed, this issue can impact engine performance, fuel economy, and emissions compliance. Prompt diagnosis and repair are recommended to prevent further damage.

Common Symptoms for DTC P0079 #

When code P0079 is present, you may notice several warning signs. The severity and frequency of these symptoms can vary based on vehicle design, engine condition, and driving habits. Typical symptoms include:

• Check Engine Light illuminated
• Rough or irregular idle
• Decreased fuel economy
• Reduced engine performance or power loss
• Hesitation or stumble during acceleration
• Poor emissions test results
• Occasional stalling (less common)

Probable Causes for DTC P0079 #

Several factors can trigger the P0079 fault code. The most frequent causes, ranked from most to least common, include:

1. Faulty exhaust valve control solenoid (sticking, open, or shorted internally)
2. Open or shorted wiring in the solenoid circuit (damaged, corroded, or disconnected wires/connectors)
3. Poor electrical connection at the solenoid or ECM harness
4. Low system voltage (weak battery, poor charging system)
5. ECM/PCM malfunction (rare, but possible)
6. Oil contamination affecting solenoid movement or electrical contacts

Step-by-Step Diagnostic Process for P0079 #

Properly diagnosing P0079 requires a logical, stepwise approach. Rushing or skipping steps may lead to unnecessary parts replacement. Here’s a proven diagnostic roadmap:

1. Scan for DTCs: Confirm P0079 is present and check for related codes (especially camshaft or VVT system codes).
2. Inspect the solenoid: Visually check the exhaust valve control solenoid and its connector for damage, corrosion, or oil contamination.
3. Check wiring: Inspect wiring between solenoid and ECM for breaks, pinched spots, or exposed wires.
4. Test the solenoid: Using a digital multimeter, measure resistance and check for internal shorts or opens per OEM specs.
5. Test circuit voltage: With the key ON, measure voltage at the solenoid connector. Compare to OEM values.
6. Wiggle test: Gently flex wiring harness while monitoring the code or test results to identify intermittent faults.
7. Check system voltage: Ensure battery and charging system are healthy (12.4V+ at rest, 13.5–14.5V running).
8. Test ECM/PCM: If all else checks out, use a scan tool with bi-directional controls to verify ECM function (rarely needed).

Possible Repairs for P0079 #

The most effective repair will depend on the root cause identified during diagnosis. Typical solutions include:

• Replace the exhaust valve control solenoid if found faulty or out of OEM specification.
• Repair or replace damaged wiring or connectors in the solenoid circuit.
• Clean electrical contacts and remove any oil or corrosion from connectors.
• Correct low system voltage by servicing the battery or alternator as necessary.
• Replace or reprogram the ECM/PCM only if all other causes are ruled out (least common).
• Change engine oil if oil contamination is suspected to affect solenoid operation.

Is It Safe to Drive With Code P0079? #

Driving with P0079 is not recommended for extended periods. While some vehicles may continue to run with minor symptoms, the underlying issue can worsen over time. Potential risks include degraded engine performance, increased emissions, and possible engine damage if the problem affects valve timing severely. If the Check Engine Light is blinking, or if you experience severe drivability issues, stop driving and seek professional help immediately.

Vehicles Most Commonly Affected by P0079 #

Based on field data and repair trends, the following vehicles are more frequently associated with P0079 (but it can occur on any model equipped with VVT/VCT technology). Always consult your OEM service information for specifics.

• Honda/Acura (Accord, Civic, CR-V, TL, MDX with VTEC/VTC engines)
• Toyota/Lexus (Camry, Corolla, RAV4, ES/IS/GS with VVT-i)
• Hyundai/Kia (Elantra, Sonata, Sorento, Optima with CVVT)
• Ford/Lincoln (Fusion, Escape, Edge, MKZ with Ti-VCT)
• Nissan/Infiniti (Altima, Sentra, Maxima, G35/G37 with CVTCS)
• GM/Chevrolet (Malibu, Cruze, Equinox, Traverse with VVT engines)

Common Mistakes & Best Practices for P0079 #

Missteps during diagnosis and repair of P0079 can lead to wasted time and money. Here’s what to avoid—and what to do instead:

• Skipping the electrical inspection: Always check wiring and connections before replacing the solenoid.
• Ignoring oil condition: Dirty or viscous oil can affect solenoid operation—change oil if overdue.
• Using non-OEM solenoids: Aftermarket parts may not meet OEM specs—use genuine or high-quality replacements.
• Clearing codes without fixing the cause: The code will return if the root problem isn’t addressed.
• Not checking for related codes: Camshaft/crankshaft correlation or VVT system codes may reveal deeper issues.

Quick FAQ for DTC P0079 #

Still have questions? Here are concise answers to the most frequent concerns:

• Q: Can I simply clear the code to fix the problem?
  A: No. Clearing the code without repairing the underlying issue will only make the code (and symptoms) come back.
• Q: How urgent is a P0079 code?
  A: While not always an immediate breakdown risk, delaying repairs can lead to higher fuel consumption, reduced power, and even engine damage if the VVT system malfunctions severely.
• Q: Is this a DIY repair?
  A: Basic electrical checks and solenoid replacement can be DIY-friendly with the right tools and knowledge, but accurate diagnosis is crucial. Consult an expert if unsure.