P0079
Exhaust Valve Control Solenoid Circuit Low (Bank 1)P0079 is a generic OBD-II powertrain diagnostic trouble code: Exhaust Valve Control Solenoid Circuit Low (Bank 1). It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0079 means
P0079 is stored when the Powertrain Control Module (PCM) detects a "circuit low" condition on the Exhaust Valve Control Solenoid circuit for Bank 1. In Variable Valve Timing (VVT) systems, the PCM drives the exhaust camshaft oil control solenoid using a PWM signal typically modulated between ground and the supply voltage. A "circuit low" fault means the PCM measures a voltage on the solenoid signal line that is persistently below the expected threshold, most commonly caused by the circuit being shorted to ground, the solenoid coil failing with near-zero resistance, or a wiring fault pulling the control line down. When P0079 is active, the PCM is unable to reliably energise the exhaust VVT solenoid on Bank 1, leaving the exhaust cam phaser locked in a fixed position. This prevents the engine from optimising valve overlap for different operating conditions, resulting in degraded low-end torque, rough idle, higher emissions, and reduced fuel economy. On V-configuration engines, Bank 1 is the side containing cylinder number 1. P0079 often accompanies P0078 or exhaust camshaft position performance codes, and the diagnostic path should include both electrical testing and an engine oil inspection.
Common causes
Most-frequently reported root causes when P0079 is logged.
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1
Exhaust valve control solenoid coil shorted internally (near-zero resistance), pulling the circuit low
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2
Short to ground in the solenoid signal wire or harness
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3
Damaged wiring insulation allowing the control wire to contact the engine block or other grounded metal
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4
Corroded or oil-contaminated connector creating a low-resistance path to ground
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5
PCM output driver failure presenting a constant low signal (rare)
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6
Aftermarket wiring splices or previous repair work introducing an unintended ground
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7
Oil sludge causing solenoid coil overheating and eventual short-circuit failure
Symptoms drivers notice
How to diagnose P0079
A typical diagnostic flow when this code is present.
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1
Connect a scan tool and confirm P0079 is current; record freeze-frame data and note any companion VVT or cam position codes
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2
Visually inspect the Bank 1 exhaust VVT solenoid wiring harness from the connector back toward the ECM for damage, chafing against hot components, or signs of heat damage
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3
Disconnect the solenoid connector and measure winding resistance — a healthy coil reads 6–15 ohms; a reading below 5 ohms or shorted to the solenoid body indicates internal coil failure
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4
With the harness connector disconnected and the ignition on, measure voltage on the signal wire to chassis ground; a persistent low reading (below 0.5 V) with the connector unplugged confirms a wiring short to ground
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5
Inspect the connector for corrosion, pushed-back pins, or oil contamination and clean or replace the connector as needed
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6
Use a bi-directional scan tool to command the solenoid on and off while monitoring live data; if current draw is excessive the solenoid is likely shorted
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7
If wiring and solenoid test good, perform ECM output circuit verification before considering ECM replacement
Related powertrain codes
Frequently asked questions
Is P0079 serious enough to cause a no-start?
Generally no — P0079 typically keeps the VVT system disabled but the engine will still start and run. However, if the short is severe enough to damage the PCM output driver, additional driveability problems could arise. Repair should not be deferred for long.
What is the most common repair for P0079?
Replacing the exhaust valve control solenoid resolves approximately 70% of P0079 cases. The remaining cases typically involve a wiring harness short to ground or a damaged connector. Full electrical testing before replacement prevents unnecessary parts costs.
Can a bad oil change interval cause P0079?
Indirectly, yes. Degraded or sludged engine oil can cause the VVT solenoid to overheat or jam, eventually leading to coil failure and a short-circuit condition. Maintaining the manufacturer-recommended oil change intervals significantly reduces VVT solenoid failures.
Does P0079 affect only V6/V8 engines?
No. While "Bank 1" terminology is most commonly associated with multi-cylinder engines, some inline four-cylinder engines with dual VVT systems also use bank designations. Check your vehicle's service manual to confirm whether P0079 applies to your specific powertrain.
Disabling P0079 in software
RaceTune can permanently disable P0079 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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