Powertrain, shared range

P3456 Cylinder 7 Exhaust Valve Control Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P3456 would flag a cylinder 7 exhaust valve actuator whose control line is shorted to supply voltage. No manufacturer documents this code publicly. According to NHTSA's summary of the DFM system, GM drives its deactivation solenoids with peak-and-hold current drivers for fast, repeatable switching, and one solenoid serves both valves of the cylinder, so a short to power is caught under the intake-side code P3452 instead (below 0.5 ohm to power with the driver on, 20 of 25 samples, Type B). CARB requires such a check for any emission-relevant output, which is why the exhaust code exists at all. A short to ground on the same channel is P3455, an open circuit P3453, a mechanical fault P3454.

Likely causes

Actuator wire of cylinder 7 shorted to battery voltage
Exhaust actuator coil with shorted turns
Current driver in the control module failed

Symptoms

  • Check engine lamp on
  • Engine does not enter reduced-cylinder mode

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

P3453P3454P3455P3452P3400

References: law.cornell.edu, static.nhtsa.gov, gsi.ext.gm.com.