[bimmerinalong]

Ok, first of all, hello, this is my first post on this forum. I hope to contribute info I learned about these cars to this forum as well as learn more from members.

As this is going to be a unusual issue, I want to document it here just in case someone else needs info from this thread.

tl;dr below.

2007 335i 01/2007 build E90 100% stock no lights/CEL on cluster

As title says, I was driving along as usual on the road when I approached an intersection with a red light and right as a came to a stop bam the car shut off.
No warning, no electronics, nothing. Like the key was taken out and battery was disconnected. IN THE MIDDLE LANE.

Fast forward to being pushed by some guys to a nearby parking lot (I owe them one) I then started noticing the hazard button illumination flickering very quickly and erratically while sitting in drivers seat. Hmm.
I messed with the car, checked battery connections, put key in ignition, pressed start button, no response.

Hooked up my friends jump pack, poof everything turned back on. HUH?

Something felt off because the battery is fairly new. So I took a risk. I disconnected the jump box, and shut it off. Then attempted to start it again without jump box. Started up just fine.

Instead of towing it, I drove it home, and parked it. I did some diagnosing.

Now I know what you're thinking. The battery is bad, or the b+ cable that goes to the junction box is toast.

This is where it starts getting strange.

First I checked codes. 2 fault codes in memory are 2DEC and 2E77.

Alternator charges fine, car starts up fine. Checked voltages with a multimeter. Battery was replaced a couple months ago. 13.8v+ while running/under load and 12.6v engine off. Battery terminals are tight. Starts up quickly with high starter RPM.

I took the glove box out and did a shake test of the junction box, battery cables in trunk, distribution block on top of battery and power cables that run across the engine bay with engine running. Nothing happened.

Recall of the b+ cable does not apply to this car. (01/2007) The b+ cable has a terminal lug that you put through a threaded stud and tighten down with a nut instead of the slot style terminal.
I still decided to remove the junction box anyway and inspect the box, all wires and terminals thoroughly. Cable, wires and box looked clean with no signs of corrosion anywhere.

I put it back together, and well now I'm stuck at a conundrum. If the battery was bad, I wouldn't have been able to start it again without the jump pack, and after and after. If alternator was bad, it would have caused this, but I would have not been able to continue driving after restarting. This means the alternator and battery are fine, and it drove fine back home. HUH.

What do you think? Are there other ground points or cables I don't know about I should check next? Other things to check? I'd like some input.

Thanks. Happy new year.

tl;dr: Approached a red light at intersection, car shut off completely. No electrical power as if key was taken out and battery disconnected. Pushed to a parking lot. Noticed erratic flickering hazard warning triangle light on dash. Car would not react or respond to anything. Hooked up jump pack 10 mins later, turned back on. Removed jump box, turned off car, started up fine without jump box. HUH? Drove home, parked, checked voltages with multimeter, good voltages. Checked/shake tested battery distribution block, battery cables, cables under hood, junction box behind glove box all while engine running and no change. Makes no sense.

[StradaRedlands]

I'd guess a loose connection at the battery, one of the terminals or the connectors. Did you really pull and prod on all of them?

[bimmerinalong]

Originally Posted by StradaRedlands

I'd guess a loose connection at the battery, one of the terminals or the connectors. Did you really pull and prod on all of them?

Yes all cables in trunk and distribution block I messed with

[lordnikon]

Has the voltage regulator ever been replaced? Also check the ground straps

[bimmerinalong]

Yes the voltage regulator was replaced a couple months ago with an oem unit

[gbalthrop]

Originally Posted by bimmerinalong

... 2007 335i 01/2007 build E90 100% stock no lights/CEL on cluster. As title says, I was driving along as usual on the road when I approached an intersection with a red light and right as a came to a stop bam the car shut off... I then started noticing the hazard button illumination flickering very quickly and erratically while sitting in drivers seat... Hooked up my friends jump pack, poof everything turned back on... I disconnected the jump box, and shut it off. Then attempted to start it again without jump box. Started up just fine... I drove it home, and parked it. I did some diagnosing. [Suggest you BEGIN with learning HOW the 3 B+ Cables supply battery voltage -- see below. AND recognize that GROUND completes circuit -- is as necessary as 12V+ Supply]...2 fault codes in memory are 2DEC and 2E77... 13.8v+ while running/under load and 12.6v engine off. Battery terminals are tight. Starts up quickly with high starter RPM...

Fault Codes are CLUES to diagnosing the issue (Along WITH understanding Electrical CIRCUITS). Here are BMW Fault Code Lookup Definitions of your two codes, along with Links to Fault Info Sheet for each:
2DEC | DME: Power management, battery msd80 | Engine electronics
https://bmwfault.codes/XMLDiagView?d...AAMwA1ADAANAA=

2E77 | DME: Firing, voltage supply | msd80 | Engine electronics
https://bmwfault.codes/XMLDiagView?d...EAMAA5ADAANAA=

2DEC indicates DME detected System Voltage < 9.52V;
2E77 indicates DME detected NO Ignition voltage on ANY cylinder. If you have NOT already cleared those faults, I would suggest reading "Freeze Frame Data" of EACH fault for any system voltage data retained in DME fault memory. I'll attach ISTA ScreenPrints and photos of Battery B+ Cables, as well as Transfer Points, to NEXT Post.

You have an intermittent LOOSE CONNECTION, which could be a ground strap, one of the B+ Voltage Supply Cables, corroded Transfer Point, etc. Since you have "jiggled" some of the B+ Voltage Supply cables, loose connection is probably in something you did NOT "jiggle".

As with ANY intermittent fault, you have to either use FF Data to see what actual voltage was at moment fault was saved, OR you have to measure voltage with DMM while fault is Active/Present. If there is ALWAYS some "Voltage Drop" due to a loose or corroded connection, you might get some clues by measuring voltage with DMM (1) at Jumpstart Terminals under Hood, and (2) at battery POSTS (inside terminals) in trunk:
a) with ignition OFF;
b) with Ignition ON;
c) with engine running.

We're looking for difference between 1) & 2) when measured at EACH of conditions a), b), c).

Otherwise, you need to measure voltage at each of those points, PLUS at X13020 on Right Side of JB Fuse Panel (under glovebox), WHEN "NO Power"/ No Crank condition is PRESENT.
George

[gbalthrop]

Attached are ISTA ScreenPrints related to 1/2007 build 335i E90 per prior post, and also photos of 3/2007 328xi components.
George

[bimmerinalong]

Valuable info. Thank you George, I will do voltage drop testing based on your explanation. I’ve seen your name a lot around this group when I would look up threads for info, I always favored your in-depth explanations lol

[bimmerinalong]

UPDATE: The issue was simply a loose and partially corroded negative battery terminal. It seems that the corrosion was caused due to a missing vent for the battery. For anyone reading this, make sure all connections and terminals are tight and you have the battery vent connected in the trunk.