We have a 2002 Peugeot 307 Rapier. It had been running fine but finally a day came when it started showing up anti-pollution fault. We got it checked but the local garage couldn't resolve it. We kept running the car as it would run fine but sometimes it would reset itself (I would find it out by date and time resetting back to zero). Sometimes the car would need a jump start and after that it would work fine again.

Few months down the line the battery died. We replaced the battery but connected the terminals wrong way round. We saw a bit of smoke from one of the battery terminal, upon that, we disconnected the battery and then connected it the right way round.

After that, we tried to start but the engine won't start, it would turn up but it won't start. We called the AA, they said that there might be a problem with the ECU because they can't see any response coming from the ECU. I then took it to a local garage, the checked it and told me that the ECU has gone.

I showed it to my uncle (who is a test engineer) he opened the ECU and checked the circuit. He told me that he can't see anything connection burnt or any problems with the within the circuit.

Now I am not sure what to do. Can you please help me as to

1. what can go wrong, which components may be damaged because of the wrong battery connection
2. it is worth spending money on this car