[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

[StradaRedlands]

Originally Posted by gbalthrop

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.

I resemble this comment!!!

[gbalthrop]

Originally Posted by StradaRedlands

I resemble this comment!!!

I "resembled that comment" (willfully ignorant of electrical circuits) until I was nearly 50 years old. It's easier to understand
stuff you can SEE. Electrons are theoretical, & understanding Circuit Diagrams requires learning new symbols & conventions.

It's just a new/different skill that takes time to learn & practice. Start simple with a $10 Multimeter from HFT or Amazon,
measuring Voltage of AAA to D Cells, 9V batteries, your 12V car battery, etc. Lots of helpful stuff you can Google.

Having spent ~ 20 years on Jag Forums, I found that most Brits are even more "in the dark" about electrical circuits
than US. Human Nature to "avoid" learning something new, requiring learning NEW Concepts.

Attached are Symbols & Conventions as used in Bentley & ISTA wiring diagrams/ SSP Documents. If someone
understands those, they can make sense of the diagrams, & appreciate the details involved.
George

[StradaRedlands]

Originally Posted by gbalthrop

Having spent ~ 20 years on Jag Forums, I found that most Brits are even more "in the dark" about electrical circuits than US.

That explains Lucas!

[Efthreeoh]

Originally Posted by ctuna

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

On every car I've owned, blank fuse spots do not have both female spade connectors of the circuit, so adding the fuse does not complete the circuit. I can't say that is true for every car, but the E9X seems to be the same.

[Efthreeoh]

gbalthrop , I still gotta ask, how is it possible to install the battery backwards in a 328i E90? I just don't think it is possible with the factory cables without some serious manipulation and dissection of the cables, especially the BST. I think the OP bought the wrong battery with reversed post polarities.

[rt7085]

What people do not realize: Fuses are there to protect the harness. They are not there to protect the ECU in the first place, however they do in most cases as fortunate by-product, but not in all cases.

Notice that most ECUs in a car have NO a local fuse on the ECU itself. That is because the ECUs must be designed to deal with the full voltage range of -14V (reverse voltage) to 37V (load dump) with the normal operating range typically from approx. 6V to 17.5V for modern cars. Different protection behavior is expected across the full voltage range.

Under reverse polarity conditions, harness protection on older cars may be implemented with a big series diode right behind the ECU's battery connector. It won't conduct when you apply reverse voltage. For high current ECUs, is it a reserved diode shunt to ground: When you apply a reverse voltage, it conducts and thus blows the fuse being a 'deliberate short'. And thus it protects the harness. (It is really a 27V zener so it also protects for over voltage) In modern ECUs, they use a bidirectional high side switch controller, so a self-resettable active fuse. That is the best but most expensive solution.

Under reverse polarity conditions, blowing a fuse is not a guaranteed thing. When a lot of ECUs conduct current together under reverse polarity conditions, the battery sees a very high current load. The terminal should have seriously acred when installing it. The wires might have gotten hot right away. The voltage sags and this sagged voltage will actually slow down or even prevent the fuse(s) melting.

The point of all of this explanation is that when you 'somehow' reverse the battery, all ECUs see possible enormous power stress trying to blow their fuse with their input protection. As a result, many ECUs may have seen damage. Now the car is a zombie. ECUs may still work, but some might fail in the future. Get ready for a witch-hunt. It is a bad situation.

I am still at a loss how the battery was installed in reverse with all the mechanical protection that is implemented to prevent this in this car.

[Mike K]

OP is nowhere in sight? False alarm?

[Efthreeoh]

Originally Posted by Mike K

OP is nowhere in sight? False alarm?

False something...

[gbalthrop]

Originally Posted by Efthreeoh

gbalthrop , I still gotta ask, how is it possible to install the battery backwards in a 328i E90?
I just don't think it is possible with the factory cables without some serious manipulation and dissection of the cables,
especially the BST. I think the OP bought the wrong battery with reversed post polarities.

Well, for those who are "Obliv-R-Us", anything is possible.

If you have the Correct Battery, if you rotate it 180 degrees, the Positive Terminal is now at the rear. However, both
Terminals are now on Inboard Side of Battery, instead of Outboard, next to fender. If you have Rear Power Distribution
Panel, on top of battery, like mine (Photo attached), can't fit inboard forward post.

Additionally, Positive Battery Post is LARGER than Negative. One would not only have been totally oblivious to details
removing old battery, &/or comparing old & new batteries (if OP is NOT a troll, sounds like he gave salesclerk the old
battery & installed replacement on site). Lots of questions. Some false theories. No response from OP. This will be
17th Post in thread. Folks are getting "Weirder" every day.
George

[Suvorovo]

It takes a village to own a BMW.

[charleskeyz]

Originally Posted by gbalthrop

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 [...]

I work as a lot Tech at a local used car dealership. I have BimmerCode BimmerLink a box full of obd2 basic code readers. A couple heavier duty scan tools. I just got a K/D-CAN cable with a switch. I have a laptop and am currently installing INPA and ISTA on. Yes I have a multimeter.

I figured out the fuse mixup and got it to start. Drove it to the post office… realized none of the windows work, the headlights don’t work and the heat doesn’t work. Pulled the footwell out and sent it to a euro shop in Hollywood, FL that reprograms FRM3 modules.

Before I pulled the footwell, I checked the codes…. It was throwing like 30 codes. I cleared them…. 15 popped back up.

I’m praying the footwell is not too damaged and they are able to reprogram it. Also praying this fixes everything. Not holding my breath tho. I have already been checking salvage yard inventory for 3 series’s.

Oh I forgot to mention this all started because a loose quart of oil leaked on my battery lol. 🤦🏽‍♂️ I replaced the fusable link and dumped a bucket of diatomaceous earth in the trunk and soaked up the majority of the oil. All before I got it started.

My concern was that the car was losing power on my drive back from the post office. So I might have more than a few problems still.

Thank you guys for all the help. This is an amazing forum with some of the best people. To everyone who took their time to respond to my post thank you.

I will post updates when I get the footwell back.

[charleskeyz]

Originally Posted by gbalthrop

Additionally, Positive Battery Post is LARGER than Negative. One would not only have been totally oblivious to details

Yup I know. I literally shaved the terminal down and pounded the connector on with a hammer, not realizing the entire battery was dropped in 180 degrees backwards. 🤦🏽‍♂️🤯😞🤷🏽‍♂️ it was dark and cold.

[charleskeyz]

Originally Posted by gbalthrop

17th Post in thread.

My apologies on the delayed response. I was busy reading all 20 pages of the FRM3 FOOTWELL module pinned post. And processing everything.
I debated ordering an EEprom reader and attempting to repair the footwell myself. I eventually decided it would make more sence to send it to a pro.

And yes I had to literally force the battery to take the reverse polarity. Read my full response above.

Thank you again for taking the time to respond. I appreciate any and all advice.

[e91Owner]

I would love to see a picture of what this looked like installed backwards. I can’t even fathom how that is physically possible as others have said.