P0079🔧 Variable valve timing (exhaust camshaft oil control solenoid)Stop and fix promptly

P0079: Exhaust Valve Control Solenoid Circuit Low Bank 1 (Meaning, Causes, Fixes)

Reviewed 2026-10-24 · Based on 2 cited source(s)

What P0079 means

On engines with variable valve timing, the engine computer (ECM/PCM) moves the camshaft by sending engine oil through a control solenoid. OBD-Codes.com explains that the computer drives this solenoid with a pulse width modulated (PWM) signal and watches that signal; if the voltage is below specification, it sets P0079 and turns on the check engine light. Bank 1 is the side of the engine with cylinder number 1 (verify for your engine), and OBD-Codes.com says the exhaust valve control solenoid is usually on the exhaust manifold side of the cylinder head. It is a generic code that applies to all makes from 1996 on, though repair steps vary by model. RepairPal describes the same part: a solenoid that uses oil pressure to let the PCM adjust when the exhaust valves open and close, with P0079 set when the PCM finds an issue with the solenoid's signal. The sources differ in a few ways. OBD-Codes.com describes an electrical fault, a short to ground in the wiring or the solenoid, while RepairPal lists engine oil problems among the common causes and an oil and filter change as the common repair. RepairPal's severity (Urgent) and its 'engine may not start' symptom are also stronger than anything OBD-Codes.com lists, and RepairPal's title leaves out the bank. OBD-Codes.com says this code is similar to P0078 and P0080 and may be accompanied by P0027.

Severity: can I keep driving?

Stop and fix promptly

Get it checked soon and avoid hard driving until then. RepairPal rates P0079 Urgent, meaning immediate action is needed, and lists decreased engine performance, higher fuel use and, in some cases, an engine that may not start. OBD-Codes.com gives no severity rating and lists milder symptoms: the check engine light, poor acceleration and lower fuel economy. Check your engine oil level right away, since RepairPal lists low or wrong-spec oil among the causes.

Common symptoms

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

  1. Wiring harness shorted to ground (OBD-Codes.com), or another wiring issue (RepairPal)
  2. Exhaust valve control solenoid shorted to ground or failed (OBD-Codes.com, RepairPal)
  3. Engine oil level too low (RepairPal only)
  4. Engine oil that doesn't meet the manufacturer's requirements (RepairPal only)
  5. Faulty engine computer (ECM/PCM) (OBD-Codes.com, RepairPal)

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

  1. Check the engine oil level and make sure the oil matches your owner's manual spec; RepairPal lists low or wrong oil as common causes and an oil and filter change as the common repair.
  2. Find the bank 1 exhaust valve control solenoid, usually on the exhaust side of the cylinder head on the cylinder 1 side, and look for chafed wires touching metal, damaged insulation or a bad connector.
  3. OBD-Codes.com notes the solenoid can be switched on its power side or its ground side depending on the vehicle, so check a factory wiring diagram to see how your circuit works before testing.
  4. To check for a short to ground in the wiring, OBD-Codes.com says to unplug the computer connector, set a multimeter to volts, put the positive lead on the battery positive and the negative lead on each solenoid wire. If the solenoid is grounded to the chassis, test the power lead at the computer harness; there should be no voltage. Voltage present points to a short to ground, which you find by unplugging connectors and working back toward the solenoid.
  5. To check the solenoid itself, OBD-Codes.com says to put one meter lead on a known good ground and the other on each solenoid terminal. Low resistance to ground may mean the solenoid is shorted internally.
  6. If wiring and solenoid test good, OBD-Codes.com suggests comparing the duty cycle commanded on an advanced scan tool with the actual signal at the solenoid using an oscilloscope or graphing multimeter at different engine speeds and loads. No signal from the computer may mean a computer fault.

Typical fixes

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

  • The engine won't start or runs poorly along with the code
  • You don't have a wiring diagram, multimeter or a scan tool that shows solenoid duty cycle
  • The code returns after an oil change and a wiring repair or new solenoid
  • Other camshaft timing codes such as P0027, P0014 or P0011 are also set
  • Tests point to the engine computer, which may need programming to your vehicle

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Can I drive with P0079?

Only carefully and for a short time. RepairPal rates it Urgent and says the engine may lose performance or even fail to start, while OBD-Codes.com lists poor acceleration and lower fuel economy. Check the oil level first and get it diagnosed soon.

What does 'circuit low' mean in P0079?

OBD-Codes.com says the computer watches the voltage of the signal it sends to the exhaust timing solenoid, and P0079 sets when that voltage is below specification. Its listed causes are a short to ground in the wiring or inside the solenoid, or a faulty computer.

Can low oil cause P0079?

RepairPal lists low engine oil and oil that doesn't meet the manufacturer's requirements as common causes, because the timing solenoid works with engine oil pressure. OBD-Codes.com treats P0079 as an electrical fault, so check both the oil and the wiring.

How much does it cost to fix P0079?

Neither source gives a repair cost for P0079. It can be as simple as an oil change or a chafed wire, or it may need a new solenoid, so diagnose it before buying parts.

Sources

  1. OBD-Codes.com: P0079 Exhaust Valve Control Solenoid Circuit Low (Bank 1)
  2. RepairPal: P0079 Exhaust Valve Control Solenoid Circuit Low (rated Urgent)

Last reviewed 2026-10-24. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.