Hi all , it’s my 1st post so be gentle with me . I have an aygo 1.0 and I have a B2799 fault code that tells me the imobiliser is not communicating with the Ecu hence it cranks but won’t start ! I’ve swapped out Ecu,  immobiliser Ecu, key chip from a known to be  working car and got exactly the same outcome.  I think I worked out with the help of Google I have a broken wire somewhere or a bad earth ! Can somebody tell me where the Ecu s are grounded ? Any help greatly appreciated . Many thanks m