Powertrain, shared range

P3493 Cylinder 12 Exhaust Valve Control Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P3493 applies to a separately controlled exhaust valve on cylinder 12 and reports that its actuator circuit is open. No manufacturer documents this code publicly; J2012 reserves the codes for cylinders 9 to 12 for engines with more than eight cylinders. Bentley's W12 and the Lamborghini Aventador V12 shut off banks; Bentley explicitly keeps the valves operating, and Lamborghini describes only the switch to six cylinders below 135 km/h. A GM patent treats the exhaust valves as a step of their own, stopping them before the intake valves, while GM's later production design drives both valves of a cylinder from one solenoid. An open exhaust circuit on cylinder 12 therefore points to a rare design. P3495 and P3496 are the short-circuit codes, P3494 the function, P3489 the intake side.

Likely causes

Wire to the cylinder 12 exhaust actuator open
Coil of the cylinder 12 exhaust actuator interrupted
Exhaust actuator connector corroded
Control module output failed

Symptoms

  • Check engine lamp on
  • Partial-cylinder operation unavailable

Repair estimate

DifficultyMediumDIY possible
Parts and labour€60–900
Time0.5–4 h

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

Parts involved

cylinder deactivation solenoidwiring harnessecm

Related codes

P3494P3495P3496P3489P3400P3497

References: law.cornell.edu, patents.google.com, static.nhtsa.gov, newatlas.com.