[charleskeyz]

So… here in Denver, the temperature has gotten much colder the past few weeks. I had a battery icon pop up on my dash 2-3 times in the same week. I figured , I have owned my 2011 328i X drive (n51) for over two years now… it would be a good time to possibly replace the battery.

Long story short, I installed the battery backwards and caused some damage. The headlights came on when the keys weren’t even in the car, so I knew something was wrong. It sounded like a secondary air pump was going possibly. I hopped in, tried to start it. It didn’t start, I smelled somthing burning… took the keys out.

Now that I have overcome the shame and worked up the courage to ask for help, I am here.

I went back and installed the battery correctly. Tried to start it. It cranked, but no start. It was cold, went home.

The next day, same thing. So I grab a pulse trickle charger and hook it to the battery and pop open the fuse box behind the glove box.

The fuse box is in such an awkward place that it’s hard to get a decent vantage point for some of the deeper fuses.

Good news, I found a fuel pump fuse that was toast. Only one I’ve found blown so far. You can tell this box took some current, many of the fuses are a bit burnt on the metal, but still good.

I noticed quite a bit of fuses seemed to be missing, so I purchased a fuse kit. (Large, regular, mini, micro sizes.. and started changing out fuses.

So now I don’t know what I mixed up, but now it won’t even crank. I’m pretty sure I put a fuse back in the wrong spot.

I’m assuming I probably have a fried alternator or starter or somthing. I am prepared to do what I have to do. It’s my daily driver so it’s not optional.

What do I do now?

[e90yyc]

Scan for codes. There will probably be a ridiculous amount, so clear them and then see what comes back. Know that some may be red herrings; electrical issues can be challenging to diagnose.

Possible you’ve fried a few modules, but it’s hard to say. For instance, the FRM is known for being a little bitch of a module even when hooked up with correct polarity; failures have occurred just from disconnecting and reconnecting a battery for very normal work.

I know we all have to learn somehow and in the process we sometimes fuck things up. Good on you for asking for help.

With that said, how would you rank your abilities either with cars in general or this platform specifically? I ask simply because while there are surely things you can do to resolve this, you may want to get help from a trusted mechanic on this one. (Your comment about missing fuses has me concerned, to be honest…)

Check alternator diodes. They are probably toast but I like to have evidence of failure before I just replace parts. Good multimeters will have a diode test function. They are soldered to the diode bridge and aren’t (afaik) replaceable if they’re fucked. So, likely a new alternator is in order. I wouldn’t put anything less than reman OE in. Don’t go to Pep Boys.

Use your nose to track down anything that smells funny and could indicate burnt wiring or other problems. Ultimately this will be an iterative process, so start with codes.

[Efthreeoh]

I have to ask how did you even do that? If you had the correct battery, putting it in backwards where the terminals were (-) towards the front of the car and the (+) battery post at the rear of the car, both posts would be on the trunk side of the battery instead of on the fender side of the battery. I don't see how the cables would fit, there is not enough slack in the cables, especially the red positive BST on the (+) battery post.

[eastsidaz]

Originally Posted by Efthreeoh

I have to ask how did you even do that? If you had the correct battery, putting it in backwards where the terminals were (-) towards the front of the car and the (+) battery post at the rear of the car, both posts would be on the trunk side of the battery instead of on the fender side of the battery. I don't see how the cables would fit, there is not enough slack in the cables, especially the red positive BST on the (+) battery post.

That's what I was thinking. Not sure if it's even possible.

[Efthreeoh]

Originally Posted by eastsidaz

That's what I was thinking. Not sure if it's even possible.

I've done 4 battery replacements in my E90 and one for a friend with an E90, so I know the battery hook up pretty well. Using the correct battery type for the E90, I just don't see how the cables would fit, they are just not long enough. Unless the OP's E90 has been totally hacked with aftermarket cables and has no BST and no IBS (the US market 328i should have both depending on equipment level), it could be possible, but the car would be holding all kinds of codes.

[ctuna]

Replacing fuses in empty slots is a bad idea there not suppose to be there for a reason.

[gbalthrop]

Originally Posted by charleskeyz

… 2011 328i X drive (n51)... I installed the battery backwards and caused some damage... The headlights came on when the keys weren’t even in the car, so I knew something was wrong. It sounded like a secondary air pump was going possibly. I hopped in, tried to start it. It didn’t start, I smelled something burning… took the keys out. [Did you disconnect a battery terminal, or leave battery connected (backwards)? How long was battery connected backwards/ wrong polarity?]

I went back and installed the battery correctly. Tried to start it. It cranked, but no start. It was cold, went home. [How far from home is vehicle? Were you installing battery at store where you bought it/ elsewhere?]...

I noticed quite a bit of fuses seemed to be missing, so I purchased a fuse kit. (Large, regular, mini, micro sizes.. and started changing out fuses.

So now I don’t know what I mixed up, but now it won’t even crank. I’m pretty sure I put a fuse back in the wrong spot... What do I do now?

Good news is that you have admitted making mistakes. Bad news is that you did NOT seek competent help SOONER. It's a "Guy Thing". 'I alone can fix it' complex.

The biggest lesson here -- MANY People have done this before you -- NEVER pull more than ONE fuse at a time, carefully noting its position & replacing it exactly where it came from. Preferably you should refer to a fuse chart or the wiring diagram for a particular circuit, to know what the FUNCTION of that fuse is BEFORE you remove anything. There are EMPTY fuse sockets where your model does NOT have a particular option, or that socket was empty from factory.

Fact is, MOST guys who are decent with a wrench are "Willfully Ignorant" when it comes to electrical circuits & how they work. So you're NOT any different from MOST. Only problem is that your "wake up call" may take more time/money to fix than most.

If you are willing to take the time to LEARN a new subject (Electrickity ;-), we're willing to help. Just answer the following questions:

1) Where did you purchase the battery?

2) Is the car AT/NEAR a large parts store chain such as Advance Auto/ AutoZone? They have Code Reader, FREE.

3) Can you get the Fault Codes read in 3 Modules:
a) DME (Engine Control Module)?
b) CAS Module (Car Access Module which Activates Ignition & Accessory relays, & Activates Starter?
c) EKPS, Fuel Pump Module?

4) Make/Model of any Scan Tool, or diagnostic software (INPA/ISTA) available?

5) Do you have a Multimeter? $10 at HFT or Amazon is all you need.

I would suggest seeing this as an opportunity to slow down & LEARN what information is available (ISTA circuits, which I can supply) to show HOW electrical circuits work.

I would FIRST determine WHY the Starter is no longer cranking since you pulled fuses. I will attach ISTA circuit for your 2011 328xi N51 E90 to NEXT Post. The two fuses for the CAS Module (which activates the Starter) are F36 (40A) & F55 (5A electronics). Their locations & Amperage are also shown on ISTA diagrams. If either of those fuses is NOT present in correct Socket, NO Crank.
George

[gbalthrop]

Attached are ISTA ScreenPrints referenced in Prior Post. Also attached is an enlarged Fuse Identification Chart, from Bentley,
showing Fuse Numbering & Location on JB Fuse Panel, beneath Glovebox, for 2008 & Later E9x models.

Fuse Panel Layout for earlier models Differs.
George