Parasitic Battery Drain - Using ISTA-D to Diagnose

[douglee25]

Car - 2008 e90 M3

Long story short, I've honed in that I have a battery drain issue going on with my car. Using a meter I've found that my car draws 0.5 amps after full shut down.

I've used ISTA-D to run an analysis and I am gathering data to hone in on the issue.

I can't say with 100% certainty at this point, but the data is leading me to believe it's the CAS module not fully shutting down.

I've updated the software in that module and no change.

So with that said, are there some typical items on this car that would typically cause the CAS module to not shut down? Door switches? Hood switch? Etc?

This have been probably been one of the most frustrating issues to troubleshoot for me ever!

Thanks!

[douglee25]

Ok so I've been there and done that... here's where I'm at -

My response will be somewhat limited on technical details because I don't have the info right in front of me.

1. With the meter inline and the car off, the car is drawing 0.5-0.6 amps while in sleep.

2. Fuse #28 - 5amp (cut off fan relay under the passenger seat and carpet) that circuit is live even though the car is in sleep mode. That circuit or relay when energized is pulling 0.3 amps.

3. According to the wiring diagram, the CAS module sends power to several circuits via the fuse box. The circuits are powered through a relay on the fuse box. This relay is also hot when the car is supposed to be in sleep. If I pull that relay the meter drops to 10mA. To summarize here... this relay powers several relays on the fuse block and one fuse is #28 which also contains a fan relay under the seat. So essentially two relays in series. Together that amperage draw adds up to what I'm seeing.

4. I can send a command from the Ista-d to send the car into sleep and the meter drops to 10mA (right where it's supposed to be). Both relays become deenergized.


Conclusion -

1. This leads me to believe either the CAS module is bad and not shutting down completely.

2. The CAS module is not shutting down because some other circuit is keeping it from shutting down.

3. I also confirmed via ista-d that no modules are becoming powered throughout the night. At least that's what ista-d says.



Can you test something for me?

1. Open the passenger door, manually move the latch on the passenger door to lock it. It clicks twice. Make sure you push it ALL the way in.

2. Open the glove box, tape the light button so the glove box light is off.

3. Remove the fuse box cover, Using your meter take a reading on fuse #28. While the fuse is plugged in. Record that.

4. Now lock the car. Immediately record the voltage again.

5. Wait 5 minutes and record voltage again on #28.

6. Wait an additional 20 minutes and record the voltage again.

7. When you recorded your last reading, remove fuse #28 and plug it in and out just enough to make contact. See if you can notice the cut off relay just under the front passenger seat clicking or not. If the line is in fact dead, you more than likely will hear nothing.


Can you post those results?

Thanks.

Doug

[douglee25]

I am happy to report that I finally fixed this issue!

I thought by posting less detail I was doing everyone a favor (HA).

I've been trying to diagnose this problem for 1.5 weeks or so. I completing testing for excessive current draw by pulling fuses initially last week. That was the first thing I did to determine I had a problem... besides having a dead battery. I was wayyy past that step in diagnosing this problem. I found the current draw to be on the CAS circuit - fuse #36. I had reviewed a ton of electrical diagrams and I was trying to determine if someone else's car mirrored what mine was doing.

For what it's worth, the CAS module sends switched power to the Terminal 30g relay on the fuse block. This relay is one of the replaceable ones on the block. The terminal 30g relay powers about 15-20 circuits or so on the board. Between the actual Terminal 30g relay and the relay on fuse #28 (fan cut off relay), those both were responsible for my 0.5amp draw. Per all the documentation I read, the CAS sends the command to power down the terminal 30g relay in 30 mins or 60 mins if you have phone communications in your car.

I waited well past 30 mins previously and the meter was still showing 0.5amp draw. I also ran ISTA-D and it did not show any modules that were staying awake by becoming active after sleep was initiated with a lock sequence.... yet my power draw was 0.5amps.

I updated the software in the CAS. No difference. I was just about ready to take a bunch of readings last night with my meter but before I decided to do that, I reprogrammed the module (not software but the code) via NCSEXPERT. I ran the parasitic draw test with my meter in line, set my alarm for 32 mins just to give the system a few extra in case, came back to the car and what do you know.... 10mA draw! #BOOM! Turns out the code must have been corrupt in some way and recoding the CAS module fixed it.

All I can say is that problem would have cost me a ton at the dealership. I guess lesson learned here is to recode a module first before spending a ton of additional time on other things.

[EW///]

I have had the same problem for about a week. I used the meter to trace them down to fuse #28 and 36 as you mentioned in your post above. I also used carly bmwhat app to pull the code and it showed fault code A732 PT-CAN awake...Clear the code and it comes right back on the next engine cycle start... This thing drives me up the wall. Thinking to replace the CAS module but glad I came across your post. What do you use to recode the cas module? I kind of clueless to this... Thanks!

[douglee25]

Just for kicks, run this test....

1. Close all windows, doors, hood, etc. Remove all accessories from the cigarette lighter just in case.
2. Open trunk but close the latch manually with a screwdriver. Disconnect the negative battery cable and hook your meter inline to measure amperage draw.
3. Lock the car. Observe the amperage draw. Should be about 0.6 - 0.8 Amps
4. Set an alarm for 35 min and come back observe amperage. Should be about 0.01 Amps.
5. If not, wait another 35 minutes and observe.

Make sure you don't touch your remote.

If amperage is still not 0.01 Amps, then you'll have to dig into the reason.

I used NCSEXPERT to reprogram the CAS module.

[douglee25]

Originally Posted by tto///M

I have had the same problem for about a week. I used the meter to trace them down to fuse #28 and 36 as you mentioned in your post above. I also used carly bmwhat app to pull the code and it showed fault code A732 PT-CAN awake...Clear the code and it comes right back on the next engine cycle start... This thing drives me up the wall. Thinking to replace the CAS module but glad I came across your post. What do you use to recode the cas module? I kind of clueless to this... Thanks!

Any update?

[EW///]

Have yet deal with it... Too busy working lately, just kept charging the battery every night so it wouldn't drain battery off completely.

[EW///]

Replaced a new battery and all the electrical gems are gone. Thus, in my case is a bad battery.

[EW///]

In my case is a bad battery... Replaced a new battery and all the electrical gems are gone.

[douglee25]

Good to hear.

[winbasic]

Just been through an exhaustive 4 week process with the dealer - turned out it was a faulty EDC module which was causing about an 8amp battery draw even when the car was supposedly locked. Replaced EDC module and all is good now...

[douglee25]

Nice!

[Lunker325]

Faulty EDC modules seem pretty common now as having parasitic power draw. Happened to me a few months ago.

[Chiquilin1996]

Hello douglee25

Thanks a lot! I have the same problem of battery drain, I updated the CAS software but without any good news...

What do you mean with "reprogram CAS module" maybe back to factory settings the module?

Could you help me?

Thanks a lot for your help!

[drwankel]

Have you actually confirmed the parasitic draw with a current clamp?

I was chasing what I thought was a parasitic draw last year, and bought a current clamp only to find there was actually no parasitic draw. The problem was an old battery. If the battery is more than 4 years old, I would absolutely replace that first if you are having odd issues, and make sure you confirm the parasitic draw with a current clamp.

[Chiquilin1996]

Hello drwankel

Yes! I Chache the battery On my way! Month ago and continue with the same problem, also insta d detect it and said to me that there are a drain between 50 and 200ma

That is the reason for i would know how can reprograme the cas as douglee25 mention

Thanks!

[douglee25]

Originally Posted by Chiquilin1996

Hello drwankel

Yes! I Chache the battery On my way! Month ago and continue with the same problem, also insta d detect it and said to me that there are a drain between 50 and 200ma

That is the reason for i would know how can reprograme the cas as douglee25 mention

Thanks!

You're not supposed to do it this way FYI but I used the base file and reprogrammed it from the laptop. I believe I used Inpa and NCSexpert.

[su_root]

I had a similar battery drain issue some years back - the culprit was those obd devices that auto insurance companies give you to plug in that monitor your driving in exchange for a policy discount.

Turned out the device wouldn't let the car fully go to sleep and it was killing the batt.