P0079 medium Severity

P0079: Exhaust Valve Control Solenoid Circuit Low (Bank 1)

Check Engine Light (MIL) illuminated with potential reduced engine performance, rough idle, and decreased fuel economy

Overview

P0079 is a generic OBD-II code indicating a low voltage or weak signal condition in the exhaust valve control solenoid circuit on Bank 1, often related to variable valve timing systems.

Common Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Rough or unstable idle
  • Reduced engine performance
  • Decreased fuel economy
  • Possible hesitation under acceleration

Most Common Causes

Faulty exhaust valve control solenoid high

Solenoid internal failure or wear can prevent proper voltage response.

Open or shorted wiring harness or connector high

Damaged, corroded, or disconnected wires/connectors in the circuit can lower the voltage signal.

Poor or high resistance ground connection medium

Inadequate grounding can cause low circuit voltage.

Engine Control Module (ECM/PCM) malfunction medium

Rare, but PCM internal voltage regulation failure can lead to this code.

Low-quality or incorrect engine oil low

Dirty or incorrect oil may interfere with VVT system operation impacting solenoid function.

Diagnostic Steps

  1. Connect a professional OBD-II scanner and verify P0079 is present with no secondary codes
    Expected: P0079 code confirmed; record any additional related codes
    Interpretation: Presence of secondary camshaft or VVT codes may indicate broader VVT issues
  2. Visually inspect exhaust valve control solenoid and associated wiring harness/connectors on Bank 1
    Expected: No visible damage, corrosion, or loose connections
    Interpretation: Damaged or corroded wiring/connector requires repair
  3. Backprobe circuit and measure voltage at solenoid with engine running or key ON
    Expected: Voltage within manufacturer specification (typically ~11.5–12.5V at power lead)
    Interpretation: Low voltage indicates wiring/circuit issue or PCM output problem
  4. Test solenoid resistance with multimeter
    Expected: Resistance within OEM specification
    Interpretation: Out-of-spec resistance suggests solenoid failure
  5. Check ground integrity at solenoid and ECM ground points
    Expected: Low resistance (~<0.1Ω)
    Interpretation: High resistance or poor ground requires cleaning or repair

Repair Solutions

Replace exhaust valve control solenoid medium
Estimated Cost: $150 - $400

OEM or equivalent quality part recommended; cost varies by vehicle model

Repair/replace damaged wiring or connectors medium
Estimated Cost: $50 - $200

Includes crimping, soldering, and insulating as needed

Clean and secure ground connections easy
Estimated Cost: $0 - $50

Routine maintenance step prior to parts replacement

Replace or reprogram ECM/PCM hard
Estimated Cost: $800 - $1500

Consider only after all wiring and solenoid circuit checks fail

Common Misdiagnoses

Avoid these common diagnostic mistakes:

  • Confusing P0079 with intake valve control solenoid codes (e.g., P0076, P0075)
  • Replacing the ECM/PCM without verifying wiring and solenoid circuit first
  • Incorrectly attributing to oxygen sensors or unrelated emissions faults

Frequently Asked Questions

What does the P0079 code mean?

Technically, the P0079 code represents Exhaust Valve Control Solenoid Circuit Low (Bank 1). It usually points to a fault within the Engine Mechanical.

Can P0079 cause engine damage?

The P0079 code is considered medium severity. Check Engine Light (MIL) illuminated with potential reduced engine performance, rough idle, and decreased fuel economy

What happens when the P0079 code is active?

Drivers often report: Malfunction Indicator Lamp (MIL) illuminated, Rough or unstable idle, Reduced engine performance when this code is present.

What parts fail when P0079 is set?

Potential culprits include: Faulty exhaust valve control solenoid, Open or shorted wiring harness or connector, Poor or high resistance ground connection. A proper diagnosis is recommended.

How much does it cost to fix P0079?

Expect to pay around $50 if the issue is a Clean and secure ground connections, but up to $1500 if the Replace or reprogram ECM/PCM needs replacement.

Is P0079 a generic or manufacturer-specific code?

This is a universal code. You might see P0079 on Ford, Chevrolet, Toyota, Honda, Nissan, or any other OBD-II vehicle.

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