: Power off the phone; hold Volume Up + Volume Down while plugging in the USB.
: Ensure that your device is indeed Oppo A3s with the model number CPH1803. You can verify this by going to Settings > About Phone.
Once the tool detects the "Qualcomm HS-USB QDLoader 9008" port, you can proceed with "Read Partition," "Format Data," or "Flash." Important Safety Warning
The Firehose file for the Oppo A3s (CPH1803) Go to product viewer dialog for this item.