No Start, low voltage issues only when it’s cold?! 2008 e92 M3

Hello, long time reader first time poster haha.

So my brother and I have had this m3 for the past 3-4 years now. And every winter we get the same stupid problem that we try to diagnose all winter long.

Basically, as soon as temperatures go under 25°C or so, voltage would drop and the car would not start no matter what, hooking it up to a portable battery works only if it’s fully charged and using the “voltage boost” button.

If the car starts once it’s usually good for the rest of the day, next day comes it’s dead again.

Now every year we get this issue and we try to fix it. Starting with the obvious, the car has had multiple new batteries (the current one is 6 months old only) and a reman alternator two years ago. None of these fixed the problem. Ever since we got the car it has a upgraded screen with CarPlay that hooks up to the main system so that it can display the android software that runs a bunch of app and the normal BMW infotainment system. The car also has airlift air suspension which was installed by the previous owner. Both were installed by reputable shops.

On top of those two, the car has an Id motion cluster and a valved exhaust. Now we are unsure if adding all these aftermarket electronics could have an impact and be the reason for this issue or not. The last time we took it to a shop they said the factory radio was the cause and that it was leaking current causing the battery to die. But after unplugging the radio and jumping the car. Next day it was dead again.

The same shop inspected the CAS which we had “fixed” the previous year and said that it was okay. So we are really unsure of what it could be. I’m tempted to just unplug everything and see what happens, as this problem has been present for too long.

I’ve reached the point where I’m trying to fix it myself as every shop we’ve gone to has said it’s a different problem and made us pay for fixes that did not resolve the issue.

I’ve searched this form countless times, and the main thing I haven’t seen anyone experience is that the issue only arises in cold weather. Because as soon as it gets warm again the car works and starts no problem which I find peculiar.

Any help is appreciated!

Frustrating and weird its only happen when it gets below 25C. It doesn't crank at all at that point?
You have confirmed current is draining when stand still (voltage below 12v?) and the battery get charged when motor running? If you have EDC, had a chance to confirm the EDC module to be good? (believe this is hinted by the shift nob light stays on). Surely the air susp and other extras are powered by ignition on, so no current drain there?

I’ve noticed that whenever the car doesn’t start, the voltage is indeed under 12v. Once the car starts it’s up to the normal 14.3v or so.

What happens when the voltage is low is that I hear the fuel pump (and maybe other electrical stuff) running but the starter doesn’t crank the engine.

The reason I’m not certain it’s an electrical drain is that sometimes the car doesn’t start, then I leave it for a few hours, then come back and it starts.

Without hooking it up or charging it.

This happend today in fact.

At 8am or so (15°C) car has 10v or so, no crank no start.

At 3pm (20°C or so) got it and it starts right away. Kept it on for a minute, turn it off and it wouldn’t start again.

7pm (15°C again) started no problem and went for a drive, no issues.

Doubt it’ll start tomorrow morning but I’ll see, unsure if it’s a mix of a few problems. After talking to my brother he says it might have started after the alternator was replaced, but he got it looked at and it was “okay” so I’m unsure.

The car seems to start more often now without the radio, but still not 100% works every time.

All the accessories do work with ignition, but I’ve noticed that the Id motion cluster has a fan that continues to run after the car is off temporarily. But that’s hooked up to the all the factory wiring with no modifications.

As for this shift knob, it has an aftermarket shifter so can’t know from that, but will look into the EDC thanks for the advice.

And no fault codes? What type of battery is it?

I would check the main power cable, the one that goes out from the fuse box in your glove compartment. It may be damaged with use (known issue, there's a TSB/recall on it) causing high resistance. I would also remove, clean and tighten all connections to the starter. And while you're in there, check the starter cable for corrosion/heat discoloration and replace as necessary.

Redd wrote

I would check the main power cable, the one that goes out from the fuse box in your glove compartment. It may be damaged with use (known issue, there's a TSB/recall on it) causing high resistance. I would also remove, clean and tighten all connections to the starter. And while you're in there, check the starter cable for corrosion/heat discoloration and replace as necessary.

Good points!

Pandatuner wrote

I’ve noticed that whenever the car doesn’t start, the voltage is indeed under 12v. Once the car starts it’s up to the normal 14.3v or so.

What happens when the voltage is low is that I hear the fuel pump (and maybe other electrical stuff) running but the starter doesn’t crank the engine.

The reason I’m not certain it’s an electrical drain is that sometimes the car doesn’t start, then I leave it for a few hours, then come back and it starts.

Without hooking it up or charging it.

This happend today in fact.

At 8am or so (15°C) car has 10v or so, no crank no start.

At 3pm (20°C or so) got it and it starts right away. Kept it on for a minute, turn it off and it wouldn’t start again.

7pm (15°C again) started no problem and went for a drive, no issues.

Doubt it’ll start tomorrow morning but I’ll see, unsure if it’s a mix of a few problems. After talking to my brother he says it might have started after the alternator was replaced, but he got it looked at and it was “okay” so I’m unsure.

The car seems to start more often now without the radio, but still not 100% works every time.

All the accessories do work with ignition, but I’ve noticed that the Id motion cluster has a fan that continues to run after the car is off temporarily. But that’s hooked up to the all the factory wiring with no modifications.

As for this shift knob, it has an aftermarket shifter so can’t know from that, but will look into the EDC thanks for the advice.

This is a very clear indication of a connection issue. With temperature change comes connection integrity by means of expansion rate.

Where exactly are you measuring the voltage from?

I’m getting the voltage from the cluster, unsure where the ECU gets it from.

Pandatuner wrote

I’m getting the voltage from the cluster, unsure where the ECU gets it from.

Okay.
Most likely that is information of the cluster itself--which isn't as reliable or absolutely representative of the car entirely. This at best could point towards a connection issue at the cluster and/or the JBE.

It would make more sense to get a multi-meter on the leads of the battery itself, the jumpstart points, then a PDM like the JBE. Then compare all of those results to figure out where the significant voltage drop is happening.

Alright I checked with a multi-meter at the engine bay and battery terminals. It was reading 11.6V and not starting.

When I hook up the battery and charger it to 13.6 it started.

I’m gonna check through out the day to see if voltage keeps dropping, and try to start it tomorrow.

My guess is that it’s leaking power somewhere, I’ve unplugged a few of the accessories to see if that has an effect.

Also to note, as soon as the car starts it jumps back to the normal 14.3v-14.5v once the alternator is running. So I believe it’s working as it should be.

Pandatuner wrote

Also to note, as soon as the car starts it jumps back to the normal 14.3v-14.5v once the alternator is running. So I believe it’s working as it should be.

Yes then the alternator seems do be doing its job.
Like the guys says, probably a good idea to check that the engine is properly grounded. One easy way is to simply measure voltage between grounding pin on the right fender and the engine itself. Should be close to zero assuming the ground strap is solid. If doing it while someone is helping you cranking, to get some current going through a possible bad connection/high resistance, you'll get more significant results.

Edit: Bumped into this, worse case maybe you have to check the starter motor next... https://www.m3post.com/forums/showthread.php?t=1319988

Pandatuner wrote

Alright I checked with a multi-meter at the engine bay and battery terminals. It was reading 11.6V and not starting.

When I hook up the battery and charger it to 13.6 it started.

I’m gonna check through out the day to see if voltage keeps dropping, and try to start it tomorrow.

My guess is that it’s leaking power somewhere, I’ve unplugged a few of the accessories to see if that has an effect.

That's a good place to measure voltage. The next place I would measure would be right at the battery itself to determine perhaps there is indeed a connection problem. Let's hope you don't have a bad battery and that something is just simply loose.

The power cables for the battery to car has many connection points. All which can contribute to an issue if there is one. If you are getting an inconsistent reading, it may be worth checking these connections.

Thanks guys for the advice, will look into it on my next free day!

I’ve checked a few times yesterday and today.

And the voltage reading form the battery, and from the jump start points has been consistent.

After the car started and then turned off again, the battery read 12.4v while the car is off. Through out the day it would slowly go down to 12.2v and then 12v.

Today I go to check and it’s at 11.8v and the car no longer starts.

I checked the grounds in the engine bay and when using the multimeter they all read the same 11.8v. And when grounding to the pin and touching the positive side to the engine block (with car off and accessory on) it would read zero. That means that the car should be grounded correctly right?

I believe somewhere voltage is leaking and draining the battery overnight but I have no clue where to even start looking, or how I would even identify the drainage location.

Would a bad main power cable drain the battery?

Or a bad starter?

I’ve even unplugged the air suspension and exhaust valve unit in case they had anything to do with it. But seems like they don’t.

Do you have anything non-OEM installed? Clearly it sounds like you have a parasitic draw causing this issue at this point.

Yes it has a few, I’ve listed them.

The car also had some problems after water came into the trunk two years back, my brother had to replace the amplifier because it got fried. And after seeing another post about the CD changer causing the battery to drain. I unplugged it today.

The battery voltage has gone down from 12.5v after I ran the car for a while to 12.2v half a day later. If it continues to go down then it’s probably not that.

This is a bit of a long shot but try to unplug the IBS connector on the battery and see if it helps.

Pandatuner Hi. I think I'm having a similar issue to you. A very very slow drain (or at least it appears so when the battery is loaded).

See my post here: https://www.m3post.com/forums/showthread.php?t=2161762

And my battery is measuring around 12.2-12.3V after a few days, despite being charged up fully to 12.6V with the CTEK.

However, when I removed the Injector fuse (near the DME box), the voltage jumped back up to 12.55V (and this was on a relatively cold day of 40 deg F).

Now I haven't disconnected the battery and measured at the terminals (unconnected), but I have a feeling that it measures at 12.6V always, but when connected to the car, there is a massive voltage drop occurring somewhere.

Perhaps, if you could also check and measure voltage at the DME terminals (fuse locations) and see if you get different voltage reading vs. at the engine bay terminals.

My suspects is perhaps a faulty CAS internal switch that is creating resistance, which impacts starting.

I have ordered new DME and Injector relays and plan to do a quick swap to see if that improves things.

Good leads.

I did one thing and I’m currently waiting for results.

I unplugged the cd changer two days ago, was at 12.2v the day I unplugged it, was 12.1 today and it started and I took it for a drive.

So I’ll leave it parked today and tomorrow and monitor the voltage to see if it goes below 12v or not.

kimiraikkonen wrote

Pandatuner Hi. I think I'm having a similar issue to you. A very very slow drain (or at least it appears so when the battery is loaded).

See my post here: https://www.m3post.com/forums/showthread.php?t=2161762

And my battery is measuring around 12.2-12.3V after a few days, despite being charged up fully to 12.6V with the CTEK.

However, when I removed the Injector fuse (near the DME box), the voltage jumped back up to 12.55V (and this was on a relatively cold day of 40 deg F).

Now I haven't disconnected the battery and measured at the terminals (unconnected), but I have a feeling that it measures at 12.6V always, but when connected to the car, there is a massive voltage drop occurring somewhere.

Perhaps, if you could also check and measure voltage at the DME terminals (fuse locations) and see if you get different voltage reading vs. at the engine bay terminals.

My suspects is perhaps a faulty CAS internal switch that is creating resistance, which impacts starting.

I have ordered new DME and Injector relays and plan to do a quick swap to see if that improves things.

Even with a new and charged battery (replaced mine s few times over the years) the voltage will drop to 12.3-12.4v soon as you open the door which starts the electronic systems onboard. As stated in BMW specs there is a few amps drained for a good while, which i enough to force to voltage down a bit. Fully charged and completely onloaded it may come up around 12.7v.

When disconnecting things such as the DME I'd assume mentioned systems simply also is disconnected resulting in...no current draing and voltage coming up.

Helmsman Hi. Thanks for the input. I just saw something interesting today and wonder if you had any pointers.

- I had the car charged overnight with the CTEK up to full capacity. With the charger plugged in still, I pushed the Start button 1 time to the KL-R position (Accessories).
- I then activated the secret BMW dash menu and read off the battery voltage. It showed 12.3V.
- I then opened up the trunk and measured the voltage with my multimeter and it was 12.50V.
- I then measured at the engine bay terminals and it was 12.49-12.50V
- I then measured at the fuse box, at the live fuse 12 and it also measured 12.49-12.50V.

Does this mean I'm getting some weird voltage drop at the module? Would you know which module is responsible for the battery voltage reading in the secret menu...is it the CAS or FRM module?