P3456 indicates that the engine control module has detected a voltage higher than expected on the exhaust valve control circuit for cylinder 7. This usually points to an electrical fault in the solenoid or its wiring that commands the exhaust valve timing actuator.
The solenoid may be stuck open or have an internal short to power, causing the circuit voltage to read high.
Damaged insulation or a pinched wire can allow battery voltage to leak onto the control circuit, triggering a high‑voltage code.
Poor contact can cause erratic voltage readings that the PCM interprets as a circuit high condition.
If the fuse/relay is compromised, the PCM may see an abnormal voltage level when trying to drive the solenoid.
Although uncommon, a malfunctioning transistor inside the PCM that drives the solenoid can cause a sustained high voltage signal; this is considered only after wiring and component checks.
No. Most cases are caused by a faulty exhaust valve control solenoid, wiring short, or connector issue. PCM replacement is rarely needed and should be considered only after those components have been tested and found good.
You can drive it short‑term, but you may experience rough running, reduced power, and possible long‑term damage to the valve train if the exhaust valve timing is not controlled correctly.
Clearing the code only turns off the Check Engine Light; if the underlying electrical fault remains, the code will return once the PCM detects the high voltage again.