Mystery Issue No Start

[BeachedBmw]

Hey everyone,

I’m having an issue with my 2010 BMW 128i (manual) and I’m hoping someone here can point me in the right direction. Here’s the situation:

A few days ago, I noticed something odd while driving. When I’d shift gears and press the clutch, it felt like the car would briefly "brake" for a split second, almost as if the brakes were lightly engaged when they shouldn’t be. Then, I shut the car down when I got to work.

When I went to start it again, I pushed the start button, but nothing happened. The dash lights came on, but no crank. I saw the red BMW lift icon and a yellow exclamation mark. Oddly enough, I was able to bump-start the car and get it running. However, now the brake lights are constantly on, and sometimes they flicker. I drove it to the shop, and the same odd behavior happened – the car still felt like it was braking when I pushed the clutch in.

The shop eventually got back to me, saying the CAS module was faulty, but they couldn’t fix it because it needs to be coded to the car. So, I bump-started the car again, drove it home, and the brake lights stayed on (flickering occasionally).

I decided to take matters into my own hands, pulled the CAS module out, and sent it off for repair. The repair shop called me back saying there was nothing wrong with it. I reinstalled it, but still no luck.

Here’s what I’ve already ruled out:

1. Fuses– Checked all fuses with a test light and pulled most of them for a closer look.
2. Battery – Battery voltage is fine, no issues there.
3. IBS cable – Disconnected it; no change.
4. Jump-starting – Tried it, no change.
5. Starter test – Jumped the starter via the white box; starter works fine.
6. Relay – Checked the starter relay in the fuse panel with a voltmeter, seems good.
7. Ground issue – Tried jumping the cables from the oil filter housing to ground, but still no start. I’ll be checking the ground cable tomorrow by pulling the panels off to inspect further.

I’ve watched every YouTube video, read through tons of forum posts, and I’m still stumped. I haven’t seen anyone else with this exact combination of issues: no crank and brake lights on all the time.

So, I’m wondering if anyone has any thoughts on this? Could it be something to do with the clutch switch or brake pedal switch? Any other ideas you all have would be greatly appreciated!

Thanks in advance for any help! I’m really hoping to get this sorted soon.

Cheers,
Dan

[cerealwars]

This is a weird one for sure. Very nice post btw!

Next thing I would look at is the brake switch/clutch switch for sure. Sounds like there must be a short somewhere.

The only other thing I can immediately think of is scanning live data with something like ProTool and looking for anything unusual to help pinpoint which circuit is acting up.

And of course, trouble codes! Do you have any?

[BeachedBmw]

Thanks for your reply Cerealwars.

I may need to pick up a scan tool. When I had the car at the shop, they gave me a diagnostic sheet with the following information:

Scan codes: 00A0C6 Terminal R: CAS module not detecting clutch or brake.

That’s all the details they provided, aside from saying that my CAS is faulty

[BeachedBmw]

Quick update, I found the ground strap. One pull with my hand and the strap disengraded into powder. Its green and nasty looking. Obviously this is an isssue. However I tried to manually make a connection with jumper cables on the ground strap bolts and still has no change. Tried to ground on engine again still no chage. brake lights still on.....

[cerealwars]

Hey man, that's still progress. Can't hurt to have a good ground on there.

Found this thread chock full of info. Post 18 has the solution for this guy's situation. Granted - different platform, different engine, but same generation of electronics. Principles should be largely the same. If you're handy with a voltmeter, and have the persistence, you'll make headway.