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Hi, everyone! I've googled about this issue, but couldn't find much info. I hope that someone could help.

I have cold start issue below -10C(14F). If it just -10C it harder to star, but if temperature drops to -15(5F) I have to I have to start 6-10 times until I get car to start. The first 2-4 times it doesn't start at all, after that car starts and immediately chokes (turns off) and I try to start until car really starts or battery dies.

I have this problem 4 years. The thing is that past 4 year that cold that I couldn't start car was only few days or week per winter.

First year I noticed problem, but I got warmer so I didn't do anything. Next year changed glow plugs, but after change it wasn't that cold so I didn't know if it was fixed. Last year winter was warm, I couldn't start the car 1 time. So I wanted to fix car for this winter. In fall I brought car for diagnostics, they told me I have to change glow plug control unit. But they didn't have it at that time, so I bought one myself and changed. I also bought USB OBD wire with INPA,DIS etc. First I connected car, there was glow control unit fault, but it wasn't current(DIS) so I cleared it and it won't came back. And there wasn't any other errors regarding to this issue.

So yesterday -10C, today -12C(10F). And I still have the same problem! Today first time tried to start, it started up but it was lauder and twitching and a bit vibrating, sounded like all cylinders wasn't working. I connected PC with INPA try to read error memory and car choked. (that was at same time within 30sec when first time car started). I had to start 4 more time to get it work. After it warmed up a bit vibrating etc. and engine sounded normal. I know if I had pc connected a bit later when car would be warmer it wouldn't choked.

Error codes I got today(DIS):
DDE - 4600 DDE: Rail-pressure plausibility pressure-controlled-positive control deviation
DDE - 4453 DDE: Injector, cylinder 5, activation - General fault - Fault currently not present

Yesterday these faults weren't there and I think if temperature increases then these faults won't be there. After car warms up a bit I can drive, turn it off and one without problems.

What could be the problem? It's only in cold weather.

Could it be battery? I've changed it 4 years ago before plugs. If it would be battery now then the car wouldn't start at all, right? Not started and then choked?

I evaluated the battery in DIS, it shows that the battery is around 50% full. When car is running battery voltage is 14,8V so alternator should be OK, right? I don't know how to test battery after night when car is not running. I think if I run DIS but won't start car it will drain the battery.

Any suggestions where to look?

Sorry for this long post, I wanted to explain in detail. And sorry a bit for my english.

Car e60 530d 2004