SOLVED: BMW E70 X5 4.8 N62 turns on but doesn't start/crank

[labatt]

I didn't post the beginning of this but did get a lot of help reading through prior threads on the same issue - so I thought I'd post something here. This is for an 2009 E70 X5 4.8.

If you search for E70 X5 won't start you get a ton of messages. They range from: Replace your battery; Replace your starter; Check your keys; Your DME or ECS might have failed; Your brake pedal might not be recognized; The battery monitor might not be working. And several other responses.

My issue.. I drove the car. An hour later I went to start it. It hard cranked and then stopped. When I went to start it again, the dashboard came on (indicators, the infotainment screen, etc.) but only the sounds of the engine doing the "pre-start"sequence under the hood.

After reading the forums, the first thing we did was go straight for the starter replacement. Also, the second thing I'll mention here is that we have an X5 4.8 (N62 engine) - NOT a 3.0. The starter is definitely NOT in the same spot. It's actually underneath the car. Here's a link to info on removing it: https://xoutpost.com/bmw-sav-forums/...r-codes-3.html. Why did we go straight for the starter?

A few tests we did that didn't require a lot of work:

• The battery was at 12.2v. A little low, but should have been high enough to crank the engine.
• We verified the car recognized the brake pedal being depressed by, well, pressing the brake and looking for the brake lights. We did a secondary test on this by setting the emergency brake and then releasing it. You have to hold the brake pedal to release it and it released. Therefore the car saw the brake pedal.
• A guy I was working with had a BMW specific code reader/tester. He was able to verify that the car saw the key when it was inside, and saw it go away when it was outside. This ruled out the comfort access system (CAS). Alternatively, I'm pretty sure that if the key locks and unlocks the doors it's recognized.
• Having the code reader was handy. The DME wasn't throwing a code.
• We visually inspected the battery monitor on the top of the battery and it looked fine.

So.. we replaced the starter and hit the on/off button. Nothing. Ugh. However because of all the false starts the battery was drained down to about 11.4. It was already dying so we figured we should get a new one just to be sure. We ran down to Autozone and grabbed one of theirs (their house brand is made by Johnson Controls who has them manufactured by Interstate - so a decent battery). Opened the battery compartment. Unhooked the battery. Put the new battery in. Put everything back together. Swore a few times at how much more complex it has gotten to change an X5 battery. Tried to start the car. Again, nothing. We were pretty frustrated.

We started thinking there was something more serious wrong. Maybe the CAS wasn't working. Maybe there was in issue with the DME.

The one thing we had read in a couple of places was that the ground straps could break. Maybe this is what happened. We grabbed the multimeter and did a bit of testing. Positive terminal in the engine compartment to the grounding bolt. 12.5v. That was fine. We tested a couple of other spots but then tested from the positive terminal to the engine. Nothing. 0v. Hmmm.. looks like a grounding issue!

We grabbed a set of jumper cables and connected them from the ground bolt to a spot on the engine away from anything rotating. Went into the car. Hit the on/off button. Vroom! The engine started right up. Yesssssss!

Anyway, looks like we'll have to replace the ground strap. There's info on that for the 4.8 here: https://workshop-manuals.com/bmw/x_s...ding_cables)_/

BTW - when we pulled out the starter it was indeed jammed up. We knocked on it a few times and it freed up but we decided to put the new starter in anyway. When we removed the jumper cables after testing the ground they were pretty warm. We're guessing 100% of the ground was going through them so the ground cable is completely gone. Our assumption is that the starter burnt out and took the ground cable with it.

Anyway.. hope someone finds this helpful!