I have changed the 4 batteries in my two key fobs for my toyota avensis and now the alarm wont work properly. I have to open car with key manually which sets alarm off. This stops when engine running for a minute. Toyota garage says to bring car in and they will recode keys for £32 plus VAT!! What a joke! Ove £40 to change key batteries!! Can anyone tell me what I need to do to sort this out myself?