Exhaust Valve Control Solenoid Circuit Low (Bank 1)
The P0079 code indicates that the Powertrain Control Module (PCM) has detected a low voltage condition in the exhaust valve control solenoid circuit for Bank 1. This solenoid is part of the variable valve timing (VVT) system, which adjusts exhaust valve timing to optimize engine performance and emissions. A low circuit voltage suggests a short to ground, open circuit, or faulty solenoid, potentially causing drivability issues and increased emissions.
1. Most Common Causes
- Faulty exhaust valve control solenoid or abnormal internal resistance
- Solenoid circuit wiring shorted to ground
- Corroded, loose, or damaged electrical connection at the solenoid connector
- Excessive resistance in the wiring due to splices, bent pins, or deteriorated wires
- Internal engine control module (ECM/PCM) failure (rare but possible)
- Blown fuse or defective VVT circuit control relay
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Rough idle or engine misfire
- Reduced engine power or hesitation
- Poor fuel economy
3. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for additional codes.
Step 2: Visually inspect the wiring and connector for the exhaust valve control solenoid on Bank 1 for damage, corrosion, or loose connections.
Step 3: Test the solenoid resistance with a multimeter; compare to manufacturer specifications (typically 6-12 ohms).
Step 4: Check for voltage at the solenoid connector with the engine running; should be battery voltage. If low, trace circuit for shorts or opens.
Step 5: If wiring and solenoid are okay, test the PCM output; if no signal, PCM may be faulty.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as it can cause poor engine performance, increased emissions, and potential damage to the catalytic converter.
How much does it cost to fix?▼
Repair costs typically range from $150 to $400, including parts (solenoid $50-$150) and labor ($100-$250), depending on vehicle make and labor rates.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.