P3456: Cylinder 7 Exhaust Valve Control Circuit High

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.

Cylinder 7 is numbered according to the manufacturer: check your engine's manual before working on it.

Symptoms

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

Most likely causes

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

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the oil level and condition before anything else
2. Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
3. Check the solenoid valve's connector
4. Compare commanded and actual angles in live data
5. Test the solenoid valve and its filter, if it has one
6. Check the engine timing if there is chain noise

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P3456 means

• P: Powertrain: engine and transmission
• 3: Generic or manufacturer code, depending on the range
• 4: Emissions
• 56: Specific fault in that system

Frequently asked questions

Can I keep driving with code P3456?

Drive little and gently. If you hear timing chain noise or the oil light comes on, shut off the engine.

What causes code P3456?

The most common causes are: actuator wire of cylinder 7 shorted to battery voltage; exhaust actuator coil with shorted turns; current driver in the control module failed.

Related codes

• P3453Cylinder 7 Exhaust Valve Control Circuit/Open
• P3454Cylinder 7 Exhaust Valve Control Performance
• P3455Cylinder 7 Exhaust Valve Control Circuit Low
• P3452Cylinder 7 Deactivation/Intake Valve Control Circuit High
• P3400Cylinder Deactivation System Bank 1

Sources

• law.cornell.edu: 13 CCR 1968.2
• static.nhtsa.gov: INRD PE25001 11969
• gsi.ext.gm.com: 19OBDG03B Diagnostics

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.