As an owner of a Series II Mazda RX-8, I have a couple of queries regarding Mazda's ECU (PCM) Car Computers. My first question to you is; Does the car's ECU (PCM) store all this programmed data and information indefinitely, even if the car is stored for long periods with 12V supply (Main Car Battery) disconnected? The second question I have is; hypothetically, if my car or any Mazda was stored for a few years without ANY use, and NO power supply (12 Volt) will the car start and work as it should? And is there an internal battery that may need replacing or renewing in the ECU (PCM). Would I have to have my car ECU re-configured?

Answer:

Interesting questions Ash, thanks. Firstly yes, the car’s computer will retain all data regarding immobilizer, vehicle configuration and the actual program file that the computer uses to run the engine. The only data that will not be retained when the battery is disconnected is “adaptive learning data”. This data is basically information that the computer has learnt and allows it to fine tune the running of the engine. This adaptive learning data will be re-learnt by the computer once the engine is running again and the vehicle is being driven, so it will not really affect the starting or running of the vehicle. However, it may take a couple of drive cycles of the vehicle to fully relearn this data. Secondly, your car should start and work as it would normally, even after that period of time. There is no internal battery that will need replacing and your ECU should not need to be reconfigured. Thanks for your great questions.