P0454 means the powertrain control module has detected an intermittent or unstable signal from the evaporative emission (EVAP) system pressure sensor or switch circuit. It points to an electrical problem with the sensor, its connector, or the wiring rather than a confirmed vapor leak. The code is stored when the sensor voltage or response repeatedly drops in and out of the expected range.
The sensor's internal circuitry can develop intermittent output as its sensing element or electrical connections wear, causing the signal to cut in and out.
Terminal fretting, moisture intrusion, or pin corrosion at the sensor connector can create an unstable resistance path and trigger an intermittent circuit code.
Vibration, heat, or rubbing against nearby components can damage the wires between the sensor and the PCM, producing momentary signal loss or shorts.
If the 5-volt reference or sensor ground circuit has a poor splice, backed-out pin, or partial open, the sensor signal can fluctuate unpredictably.
A failing PCM input circuit is an uncommon possibility; it should only be considered after the sensor, connector, and wiring have been thoroughly tested and ruled out.
Usually no. PCM failure is an uncommon cause of P0454. Most cases are resolved by repairing the sensor, connector, or wiring. The PCM should only be suspected after thorough electrical testing rules out everything else.
Yes, in most cases the vehicle remains safe to drive, though the check engine light will prevent passing an emissions test and the underlying fault should be diagnosed to avoid future EVAP issues.