E-4 can mean one of two things depending on the instructions on the display:

Blood applied incorrectly: see user’s manual - Too little blood has been applied to the test area OR the user did not apply the blood to the centre of the test area or applied it too much to one side. Repeat the test with a larger amount of blood. Apply the blood drop to the centre of the test area.

Meter error - Retest - A meter error has occurred or the meter is defective. If the error message is still displayed after turning the meter on again, contact Accu-Chek Customer Care. The meter may be defective.

Cassette? Insert new cassette - There is no cassette in the meter. Insert a new test cassette in the meter.

E-1 can mean a number of things, depending on the instructions on the display: 

​Cassette invalid: insert valid cassette - Insert a test cassette suitable for this meter type.

E-1 can mean a number of things, depending on the instructions on the display: 

Cassette expired: insert new cassette - The use by period or use by date of the test cassette is exceeded. Insert a new test cassette in the meter.​

E-1 can mean a number of things, depending on the instructions on the display:

Cassette empty: insert new cassette - This message appears if a test is started and all test areas in the test cassette have been used. Insert a new test cassette in the meter.​

E-1 can mean a number of things, depending on the instructions on the display:

Cassette defective: insert new cassette - Remove the test cassette from the meter and re-insert it, or insert a new test cassette in the meter.