what is an E1 error message on a hoover new wave 5 plus?

The machine will run the first part of the cycle then empties; then the E1 error massage appears, I then had to turn off the machine and start it on the next part of the program and again at the end of the second wash the machine will E1 after which I do the same as before and then it will complete the program.

make & model HOOVER WASHING MACHINE NEW WAVE 5 PLUS ( NEW IN 1997)