Could you reply to my update, if you can help. ThanksUnlikely that so many issues have occurred at once. This is more likely to be a single connection, disrupting communication all along a line.
The body computer, behind the OBD connector needs checking for secure connections. Also check for any dampness.
Under the windscreen, there's a chamber wher the wiper motor sits. That catches rainwater, which should drain out, through two rubber 'duckbills'. Those duckbills can block, especially with dead rotting leaves. The chamber fills with water, and overflows into the car, often onto the body computer.
Although the battery has been replaced, check the connections are secure. Also check the earth cable from battery to body and engine. At 5 years old, this should still be good, but they do corrode internally, making a high resistance, causing a multitude of electrical issues. Squeeze and flex the cable along its length. It should not feel crunchy.
Thanks for the info.@portland_bill. The mild hybrid has two batteries. The standard 12v battery under the bonnet, same as the 'normal' car. So there's no extra long earth cable to it.
The other battery under the passenger seat and is charged via the alternator when free-wheeling, no accelerator, in gear and above certain engine speed. This battery then provides the energy back to the alternator, becoming a motor and turning the (more robust) belt so assisting acceleration and starting the engine (under stop/start conditions).
It could still be an issue with the earth cable - an issue certainly known on other 500's, ECU dampness, or a loose connection somewhere. It's interesting the OP mentioned a previously loose connection but not exactly what. It might just need everything resetting properly.
As suggested, and not yet confirmed by the OP actually done, with obvoius caution, I would also be checking security of all plugs and wires particularly around both batteries, together with any dampness near the ECU. Then using a jump lead as a temporary earth to see if that helps. I'd also be checking the boot wiring loom on a 5 year old car to ensure any issue there isn't causing these crazy errors being logged.
Thanks for that. I'm surprised it is only 12v, but that at least should be a small weight penalty, so the gain in fuel economy is greater than that used to carry itself around.@portland_bill
The hybrid battery under the passenger seat is only 12v lithium and smaller in physical size than the standard 12v lead acid under the bonnet (which powers all normal systems). It is quickly drained in normal driving, providing a torque contribution when accelerating, but does recharge quickly. I would still expect a replacement to be very expensive.
The car has a normal starter, but under stop start conditions, the alternator (Fiat call it BSG, belt starter generator), restarts the engine. That works very well in practice, it's a smoother, quieter and quicker start than any other S/S car I've driven. Less wear on the starter is a bonus.
Am I correct that you are/were an ADI (as I am)? If so, you won't be impressed that the system encourages coasting by indicating on screen to select neutral when free-wheeling at speeds of below 18mph and switching the engine off on the move if done.
Hi, thanks for the info so far. Just a little history with issues. Intermittent error issues for last 6 months appearing on dash. Unable to start 2 weeks ago with lots of error lights on dash. Garage picked up car and replaced aux battery and fixed loose connection. All good. Friday had mot and minor service - all OK. Yesterday, started playing up again with errors. Today, it wouldn't start. Same errors on dash. When I did get it to eventually start, error appeared after a minute or so with clicking noise from where aux battery is located under passenger seat. Just sat in it to try again, and it started straight away and drove round the block. Plugged in car pal obd scanner and came up with OL Fault B2 and u0431 error. Any ideas? Thanks