Faulty exhaust valve control solenoid with internal short or low coil resistance; Wiring to the solenoid chafed or shorted to earth; Damaged, corroded or loose connector at the solenoid or control unit; Oil contamination or leakage into the solenoid connector or wiring loom; Low or dirty engine oil affecting the valve timing system and solenoid operation; Fault inside the engine control unit driver circuit.

P0079

Exhaust Valve Control Solenoid Circuit Low Bank 1.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
0: AreaFuel and air metering, auxiliary emission controls
79: FaultThe specific fault in that area

What it means

P0079 means the engine control unit has detected a low voltage or signal in the control circuit for the exhaust valve control solenoid on bank 1. This solenoid is part of a variable valve timing or valve lift system on the exhaust side, and the control unit monitors its circuit for faults. The code sets when the measured circuit state does not match the commanded state, which points to a short to earth, a wiring fault or a failed solenoid. Exact layout and wiring depend on the engine.

Symptoms

Engine warning light on
Rough or unstable idle
Reduced power or poor acceleration
Poor fuel economy
Engine may enter a limp mode on some models
Hesitation or uneven running at certain engine speeds

Possible causes

Faulty exhaust valve control solenoid with internal short or low coil resistancelikely
Wiring to the solenoid chafed or shorted to earthlikely
Damaged, corroded or loose connector at the solenoid or control unitlikely
Oil contamination or leakage into the solenoid connector or wiring loompossible
Low or dirty engine oil affecting the valve timing system and solenoid operationpossible
Fault inside the engine control unit driver circuitrare

How to diagnose

Read all stored and pending codes and note the freeze frame data, including engine temperature and load when the fault set
Check the engine oil level and condition, as the valve timing system relies on clean oil at the correct level
Visually inspect the bank 1 exhaust valve control solenoid, its connector and the wiring for chafing, oil soaking, heat damage or corrosion
Disconnect the connector and check the pins for corrosion, bent terminals and poor tension
Measure the solenoid coil resistance and compare it with the manufacturer specification for that engine
Check the supply and control wires for short to earth, using the wiring diagram for the specific model
Command the solenoid with a suitable diagnostic function if available and confirm it operates and the circuit responds
Clear the code and road test to see whether it returns, then recheck the data

How to fix

Replace the exhaust valve control solenoid if its resistance or operation is out of specification
Repair or replace any wiring that is chafed or shorted to earth
Clean or replace the damaged connector or terminals
Replace an oil-soaked loom or connector and fix the source of the oil leak
Correct the oil level or change the oil and filter if it is contaminated or the wrong grade
Check for an applicable control unit software update if the manufacturer lists one for this fault, and only suspect the control unit once everything else is proven good

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but performance and economy may suffer and the fault may worsen. Have it checked soon, and avoid driving if the engine runs very roughly or the oil level is low.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.