P0078
UniversalExhaust Valve Control Circuit (Bank 2) Malfunction.
Medium SeverityThis code indicates a fault within the electrical circuit that controls the exhaust valve timing on engine bank 2. This typically means the engine's variable valve timing (VVT) system for the exhaust side is not functioning correctly, which can lead to reduced engine performance, decreased fuel efficiency, and increased emissions.
⚠️ Before You Begin (Safety First)
Always ensure the engine is off and cool before working on any engine components. Disconnect the battery's negative terminal to prevent electrical shocks or accidental short circuits. Be cautious of hot engine parts and rotating components if the engine is briefly run for testing.
Common Symptoms
- Check Engine Light illuminated
- Reduced engine performance or power
- Decreased fuel economy
- Rough idle
- Engine hesitation or stalling
- Difficulty starting
Common Causes
- Faulty exhaust VVT solenoid (actuator) on Bank 2
- Wiring issues (open, short, or corrosion) in the solenoid circuit
- Low engine oil level or dirty engine oil
- Clogged VVT oil passages or screen
- Faulty Engine Control Module (ECM) (rare)
Frequently reported on: Honda Accord (2008-2012), Toyota Camry (2007-2011), Chevrolet Equinox (2010-2015), Ford F-150 (2011-2014), Nissan Altima (2007-2012)
Diagnostic Steps
- Check engine oil level and quality; change oil if dirty or low.
- Locate the exhaust VVT solenoid on Bank 2 (usually passenger side for V-engines, or the side not containing cylinder #1 if inline).
- Inspect the electrical connector and wiring for corrosion, damage, or looseness.
- Use a multimeter to check for proper voltage supply and ground at the solenoid connector.
- If accessible, remove and inspect the solenoid for clogs or damage; test its operation by applying battery voltage (briefly) to see if it actuates.
- If the solenoid is suspected faulty, replace it.
- Clear the DTCs and test drive the vehicle.
👨🔧 When to Call a Professional
If you have multiple VVT-related codes or if replacing the solenoid does not resolve the issue, it is highly recommended to consult a professional mechanic. Complex diagnostics involving oil pressure, camshaft position sensors, and ECU functionality may be required, which often necessitate specialized tools and expertise.
Commonly Asked Questions
What is 'Bank 2'?
Bank 2 refers to the side of the engine that does not contain cylinder #1. On V-type engines, this is usually the passenger side, but always consult your vehicle's service manual to confirm.
Can I drive with a P0078 code?
While you might be able to drive, it's not recommended for extended periods. The issue can negatively impact fuel economy, engine performance, and emissions, potentially causing further engine damage over time if not addressed.
Is low engine oil related to this code?
Yes, the variable valve timing system relies on engine oil pressure to operate the VVT solenoids and adjust camshaft timing. Low or dirty oil can directly cause the VVT system to malfunction, triggering P0078.
How do I identify the exhaust VVT solenoid on Bank 2?
The exhaust VVT solenoid controls the exhaust camshaft. Bank 2 is the non-cylinder #1 bank. Look for a solenoid mounted near the exhaust camshaft on that side of the cylinder head, often near the front or rear.
Do I need special tools to fix P0078?
For basic diagnosis, a multimeter and possibly a scan tool to clear codes are helpful. For replacement, standard hand tools are usually sufficient, though some vehicles may require specific torque wrenches or specialized VVT solenoid removal tools.