I have a 1999 Nissan Sentra with a 1.6 L engine. My check engine light went on. I went to the local auto parts store and they used their hand held computer to check the computer. I gave an Evap Systems Malfunction reading. I replaced the PCV valve and after a while the light went off, but it came back on. I used a Haynes manual to check the on board computer. The computer uses OBD II. I counted the number of times the Check Engine light flashed and tried to find the error code in the manual. The light flashed for 5 long followed by 7 short flashes. This code is not in the Haynes manual. Does anyone know what it means?

Error code P0445
"The PCM has determined that a short circuit condition exists in the electrical circuit for the purge control valve in the evaporative emmission control system"

The code says it's an short circuit, that means your problem is electrical. Follow the wires from the evap canister to the purge control valve and back to the ecu and you should find your problem. If u can't find it' try replacing the sensor.