I have a Volvo V70 R-Design 2009 2.0D 136bhp. It has what I have read to be a common leak from the top windscreen seal. Water has slowly crept into the car without me realising, and caused some electronic issues, and the car will no longer start. The dash displays warnings for “Immobiliser, try start again”, “DSTC service required”, and “Coolant service required”. At first when pushing the start button the car would send a bit of power to the starter but there would be just clicking (this was sometimes delayed too, and would not stop until the battery was disconnected), while the windscreen wipers were on with no control from the stalks. After taking the car apart and finding profuse condensation/dripping in the passenger footwell where the Central Electronics Module (CEM)/Fuse box lives, I dried it out using heaters to remove as much as possible, then tried starting again and this time the starter engaged properly and will turn over the engine a few times then pause and try again (is this the normal start procedure and just no fuel?), and now the wipers are behaving themselves. Better but still no cigar. I’ve taken the CEM out and checked for corrosion, and tried to de-corrode the circuit board and connectors as much as possible, although there wasn’t much corrosion there to begin with. I’ve tried again today and we’re back to clicking on start with hints of turn over.

My OBD software(s) are also unable to communicate with the ECU.

Does anyone have any suggestions as to what else I should be checking/replacing?