P2408 signals a fault in the fuel cap sensor switch circuit, meaning the vehicle's computer is not receiving the expected pressure signal from the fuel cap. The code is triggered when the sensor's voltage reading is outside the normal range.
A loose, cracked, or defective cap prevents the sensor from detecting proper pressure, triggering the code.
The pressure sensor integrated in the cap can malfunction, sending incorrect voltage to the PCM.
Corroded, damaged, or loose wiring between the cap sensor and PCM can interrupt the signal.
A clogged charcoal canister vent or stuck purge valve can cause abnormal pressure readings that affect the sensor circuit.
A rare internal failure in the PCM's sensor input circuit can generate the code, but this is uncommon.
Replacing the PCM is rarely necessary; the issue is usually caused by the fuel cap, sensor, or wiring.
A loose or defective cap is a common cause, but other faults such as sensor failure or wiring problems can also trigger it.
The sensor is integrated into the cap; replacing the entire cap is typically required if the sensor fails.
Yes, a blocked vent or stuck purge valve can affect pressure readings and lead to this code.