Xbox 360 error code E70 is an error that usually occurs when the hard drive is not found by the console.
1. Reconnect the Hard disk drive (HDD)
It is possible that your Hard disk drive (HDD) has lost its contact to your Xbox 360 and resulted to "Xbox 360 error code E70." Try to reconnect the HDD to your Xbox 360. If the error still occurs a storage device such as USB storage device and an external hard disk drive might be attached to your system. Try to remove it if it works. If it does, that storage device might be faulty.
If the error persists, test your Hard disk drive (HDD).
2. Test Hard disk drive (HDD)
"Xbox 360 error code E70” may be a result of a faulty hard disk drive. Test it, to determine the problem.
- Remove the HDD from the console.
- Connect the HDD to a working PC.
- Power on the PC. Check if the hard disk drive is detected. If it is not, it is considered faulty.
- If the PC detects the HDD, see this YouTube video tutorial to guide you on testing the HDD.
Any defect found on your Xbox 360 hard disk drive, will result in a replacement to fix the problem. If the test result as good, your Xbox 360 HDD SATA cable might be faulty, try to buy a new one.