Powertrain, generic · Fuel and air metering, auxiliary emission controls

P0078 Exhaust Valve Control Solenoid Circuit Bank 1

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

A solenoid valve on the cylinder head controls oil flow for the variable valve control on the exhaust side of bank 1. Depending on the manufacturer it drives a camshaft phaser (for example on Nissan engines) or a valve lift changeover (for example on Subaru engines). This code family reports electrical faults in its control circuit; P0078 is the general circuit fault: open circuit or short, without distinguishing between them. Some manufacturers use only this code for all electrical faults of the valve. Other manufacturers report the same valve under the "camshaft position actuator" codes instead. Valve control is then switched off or stays in its base position.

Likely causes

Solenoid coil open or shorted
Wiring or connector interrupted, chafed or corroded
Oil at the connector, e.g. from a leaking valve O-ring
Output driver or supply in the engine control module faulty

Symptoms

  • Check engine light on
  • Less power, especially at high engine speed with lift changeover
  • Rough idle possible
  • Follow-up codes for camshaft timing or misfire possible

Repair estimate

DifficultyMediumDIY possible
Parts and labour€50–350
Time0.5–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

valve control solenoid exhaust bank1valve control solenoid wiringengine control module

Related codes

P0079P0080P0084P0027P0013

References: law.cornell.edu, automotivetechinfo.com, en.wikipedia.org.