First of many faults with the car. After a successful drive back home and leaving it parked up for a bit, I had an issue starting it up. So jump leads and started it up no problem.
The problem started getting worse and was finding it was needing an assist more and more. So I hooked up the CTEK to rule out battery or alternator. I used the reconditioning mode and on the level indicator on the battery it was showing green. After a couple of days, unhooked it and went to start again and it struggled to start. I then disconnected the IBS sensor which didn't make much of a difference.
Got INPA on to check for battery voltage and noticed voltage was low while the car was running and was around 12v. I also had a fault for the IBS sensor. Its a common fault for the IBS to play up and this can cause all sorts of weird voltages.
So I found out via this thread on the 5 series forum
https://forum.bmw5.co.uk/topic/13134...t-on-a-budget/ on how to replace the IBS with the updated one.
Here's the old and new:
New one needs one of the wiring loom adapted
Part number for reference:
This had cleared the issue of the IBS failure but still not solved the issue. What was even more stranger was the fact the OEM battery was showing a green on the indicator meaning it was good. I disconnected the battery entirely and charged the battery up so it could rule out any parasitic drain.
After charging it was connected and after cranking it, was now showing 9v. I got the jump leads on to start it and while it did, the voltages were low while the car as running. There was no strange noises from the alternator so I thought it had to be the battery because as soon as the car was turned off, the battery voltage was low.
I went and got a new one from Halfords and avoided getting a Bosch. Fresh Yuasa battery was installed with the same AH rating as the OEM battery. With this generation of BMW, the battery needs to be registered. No coding required as the AH value is the same. If you do put one in with a different AH, it needs to be coded. After registering it succesfully with INPA, turned the key and it came to life straightaway no issues with a steady and healthy voltage when running.
New battery:
