P3456Cylinder 7 Exhaust Valve Control Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- 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.
- What you may notice
- Check engine lamp on
- Engine does not enter reduced-cylinder mode
- Likely causes
- PossibleActuator wire of cylinder 7 shorted to battery voltage
- PossibleExhaust actuator coil with shorted turns
- RareCurrent driver in the control module failed
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €60 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.