P3456 code meaning
Cylinder 7 Exhaust Valve Control Circuit High
Powertrain system Generic code P34xx codes Check engine light
What P3456 means
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.
P3456 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P3456
- Check engine lamp on
- Engine does not enter reduced-cylinder mode
Common causes of P3456
- PossibleActuator wire of cylinder 7 shorted to battery voltage
- PossibleExhaust actuator coil with shorted turns
- Less likelyCurrent driver in the control module failed
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Cylinder deactivation solenoidWiring harnessECM
What each part of P3456 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 3 | Mixed range: generic and manufacturer-specific codes. |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| 56 | The exact fault in that area. |
What to do next
- Note P3456 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P3456
What does P3456 mean?
P3456 means "Cylinder 7 Exhaust Valve Control Circuit High". P3456 would flag a cylinder 7 exhaust valve actuator whose control line is shorted to supply voltage. It is a generic code, so it means the same on every make.
Is it safe to drive with P3456?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P3456 fail an emissions test?
Yes, it can. P3456 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P3456 to fix?
Difficulty: medium. A typical repair takes 0.5 to 4 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P3456 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.