P0463 indicates the PCM is seeing an abnormally high voltage from the fuel level sensor circuit, which typically points to an open circuit or loss of continuity in the sensor signal path. The fuel level sensor is a variable resistor (rheostat) mounted inside the fuel tank, usually as part of the fuel pump sending unit assembly. A high-voltage condition generally means the signal wire is disconnected, the sensor has failed open, or the float mechanism is stuck.
The internal rheostat or contact wiper wears out, corrodes, or breaks, creating an open circuit. This is the single most common cause of P0463 and typically requires replacement of the sending unit assembly.
The electrical connector at the top of the fuel tank is exposed to moisture and road debris. Corroded pins, pushed-back terminals, or a broken signal wire between the tank and the PCM will produce a high-voltage reading.
The float arm can become binding, bent against the tank wall, or separated from the sensor, leaving the wiper at the full-resistance position. This is more common in vehicles that have had fuel pump service or rough fuel sender installation.
A chafed, pinched, or rodent-damaged signal wire along the chassis harness can interrupt the sensor return path, causing the PCM to see reference voltage on the signal line.
Rarely, an internal failure in the PCM's fuel level sensor input circuit can cause a false high-voltage reading. This should only be considered after the sensor, float, and all wiring have been definitively verified as good.
The definition is universal; the diagnostics are engine-specific. Open your vehicle for the codes documented for it:
Yes, it is generally safe to drive. The code does not affect engine operation or drivability, but you will not have an accurate fuel gauge, so you risk running out of fuel unexpectedly. Track mileage manually until repaired.
The code itself is not a direct emissions failure in all jurisdictions, but it can prevent EVAP system self-tests from running because the PCM may refuse to test EVAP if it cannot confirm fuel level. Many inspection programs will fail a vehicle with any stored check-engine code.
Almost never. The PCM is the least likely cause of P0463. The fuel level sensor and its wiring/connector account for the overwhelming majority of cases. A PCM should only be replaced after the sensor, float, and entire harness have been tested and confirmed good.
Not always. Many vehicles have an access panel under the rear seat or trunk floor that allows sending unit removal without dropping the tank. Check a service manual for your specific vehicle before assuming the tank must be removed.