Intermittent non-starter, electronic issue?

Agricola

Have an e90 320d which has a weird issue of late. Car doesn't start (cranking but not firing, or sometimes a couple of cranks then stops) Getting these warning lights on the dash....

........

It's an intermittent problem. Didnt start on Saturday morning, but when I came back to it a few hours later, it went first time. Discovered today that disconnecting the battery for a few seconds is able to clear it, and it starts fine. Any ideas?

biko

Do you know what those symbols mean?

How old is the battery in the car?

Agricola

Brake, cruise control and traction control warnings I think. But Ive read the 3rd one is a multipurpose warning which can be flagged for a variety of issues.

Battery is 2 months old.

bazz26

The third one is the stop/start system I think. The first suspect I'd be checking is the condition of the battery, a knackered battery can throw all sorts of warnings up on a BMW dashboard. Lots of batteries going dead lately due to cars being parked up during the lock down.

Agricola

Ok, cars been sitting since lunchtime, tried the ignition again and dash light up like a xmas tree again.
Got the CC-ID codes for each of these warning lights, this is what they are apparently.......

CC-ID 24 – DBC Dynamic Brake Control Brake Assist Failed
CC-ID 26 – Cruise Control Defective
CC-ID 35 – DSC Failed
CC-ID 50 – Tyre Monitoring Failure
CC-ID 50 – Runflat Indicator Failed
CC-ID 309 – Fuel Pump Malfunction

Assuming all of these systems couldn't have failed all of a sudden, has to be something electronic or battery.

Cerco

Since the battery is only 2 months old I would start there. Do the new battery specs meet or exceed the specs of the original battery?
You need to check the battery voltage. Check that the battery contacts are tight. Do not over tighten them.
New batteries should be registered in the cars electronics, but this should only affect the charging current so should not cause your issues.

Waterson

All of these fault codes can be linked to low voltage supply to the modules, which coupled with your non start issue would point towards the battery/charging system. The checks you can do would be to check the integrity of the battery cables at the battery in the boot, make sure they are connected securely.
Does car start from a jump via the under bonnet jump posts?

Potentially there could be a parasitic current draw; some component that is draining the battery with ignition off. Unfortunately this is a common issue on many BMW. I've seen ignition modules, infotainment units, BCM'S all cause current drains.

Agricola

Thanks for the suggestions lads.

Turned out to be the blue ECU relay in the box under the bonnet. Got it tested today and it's a dud. With nothing open will make do with a good second hand one from an e46. There no water damage in either the battery tray or ecu-box, so think ive solved it.