Look here for an explaination of the codes
Er 01 - Debris is trapped in the edge cleaning brush. Inspect and clean it
Er 02 - Debris is trapped or tangled around the agitators. Inspect and clean them
Er 04 - Left drive wheel has become overloaded. Check that debris has not been tangled around it.
Er 05 - Right drive wheel has become overloaded. Check that debris has not been tangled around it.
Er 07 - One or both of the drive wheels is not making contact with the floor. Check and clean them
Er 08 - Bumper problem. Check it is not damaged and moves freely
Er 09 - The dust container is not fitted or has not been fitted in properly. Fit the dust box by pushing it home until it locks in place
below is example of Error code 01