P0079 indicates the powertrain control module has detected a lower-than-expected voltage signal on the circuit that operates the exhaust variable valve timing solenoid for Bank 1. This usually means the solenoid, its wiring, or its connector is not allowing the commanded electrical path to complete properly. The code refers to an electrical circuit fault rather than a mechanical valve-timing failure.
The solenoid coil can open internally, short, or mechanically stick, causing the control circuit to draw too little current and register a low-voltage fault. This is the single most common cause for this code.
Chafed, melted, or pinched wires between the PCM and the solenoid can short the control or power circuit to ground, producing a low voltage reading at the PCM.
Poor pin contact, spread terminals, corrosion, or oil contamination in the solenoid connector raises resistance and can make the circuit voltage appear low.
Very low oil pressure, contaminated oil, or a clogged oil-control-valve filter screen can prevent normal solenoid operation and may contribute to circuit-related faults, though it is less directly the cause than electrical issues.
A failing output driver inside the PCM is possible but genuinely rare; this cause should only be considered after the solenoid, wiring, and connectors have been ruled out.
Short trips are usually possible, but variable valve timing faults can reduce power, worsen fuel economy, and increase emissions. It is best to diagnose and repair the issue promptly.
Usually no. Most P0079 faults are caused by a bad exhaust VVT solenoid, damaged wiring, or a poor connector. PCM replacement is rarely the correct fix and should only be considered after the solenoid and circuit are proven good.
Dirty or low oil can affect VVT solenoid operation and may set related performance codes, but P0079 specifically describes an electrical circuit low voltage condition. Check oil condition and level, but focus diagnosis on the solenoid and wiring first.
Bank 1 is the cylinder bank containing cylinder number 1. The exhaust VVT solenoid controls oil flow to the exhaust camshaft phaser on that bank; its location varies by engine layout.