LG intellowasher 7kg wd-1045fh keeps displaying DE?

Though my washer is working it seems to get to minute 138 what ever programme I use and then the bell goes off like it does at the end and when you look at it is displays dE in the panel. It won't get passed this. The only way to finish any wash is to turn it off then on again and make sure you only have a cold wash which starts of past the 138 minute mark. Could this be the heating element do you think. Not sure what to do.