Intermittent complete electrical failure - Bad BCM?
 

Hello,

I got a complex electrical problem with my Z (09 370Z 6MT 62k miles) and worse it only happens about once a week, and never when I bring it to a shop. Hoping someone here might have heard something like what I am going through or can help run through diag.

What happens is that very occasionally when I turn off the Z, it completely dies. No dome light, gauges go completely dead (no red needles), doors wont unlock, no annoying beep that my lights are on/key in the dash. The start button also has no light on LOCK and the car will not start up again. I have tested the battery in this condition, full 12.6v at the battery. Over time, various parts of the car start regaining power, but I have about 3-5 minutes of what I can best describe as a "brown-out." The dome light will flicker, the door will try to unlock but just click over and over. The ignition button will eventually display Lock, but pressing it will only cycle to ACC, then power off with a flash of the gauge warning lights. Sometimes it will cycle to ON but not start the car, just attempt to do so then power off completely again. Once I go through this electrical hell, the car will eventually start and be perfectly fine for days as a daily driver.

Additionally once in a blue moon I might experience some issues in the first few minutes of driving. The lights will flicker, gauges die, car stutter for a brief second. When this happens its pretty much a guarantee that I will experience the power off issue when I'm done with my drive. Also during this drive I do notice my voltmeter swinging between 13.5v to 15v as if its tied to my tach.

This has been going on about a month and a half, not getting better or worse. I didn't do any service/repairs before this started. I can identify any pattern of when it happens (not rain/water related or other drive conditions).

Already have taken it to 3 shops (two dealerships), verified battery condition, ground cables, harness connection points, ran diags on the modules - nothing came up.

My best guess its a failing BCM, but that's a repair I'd rather not make without confirmation. Anyone have any ideas on what could be causing this issue/how to confirm a bad BCM?

Sounds to me like a power problem. Check your battery terminals and the block attached to the + terminal for corrosion, looseness, etc. If everything checks out there, get the battery and alternator checked.

Edit: Get things rechecked. You may have to do some looking around to find a competent shop.
Also check BCM grounding.

Edit Two: Check the IPDM, too.

I've seen batteries before that passed every test available, yet were bad. If there are a few internal plates that are warped and short out every once in a while, you may never figure it out.

I don't know how old your battery is, but for the relatively inexpensive price (compared to a BCM or other electrical component), I'd replace it. Even if the battery is relatively new, I've had a few batteries in my life go bad after a few months, so...

Keep us posted as to what you find.

Sounds like a bad battery. They can cause electrical havoc.

if thats the battery that came with the Z. It's time for a new one. It's 11 years old. Batteries that start going bad, but tested good. Will do some strange stuff. Most electrical system needs 10.5 volts minimum to operate. Below that. Some systems will shut down to protect it's self from voltage surges. If you are seeing swings on your volt meter. I suspect that's what is happening.

go to Walmart ,get new battery, put it in yourself, dont trust the "mechanics" there,,cheap fix if it works

Thanks all, the battery was replaced a little over 2 years ago (NAPA, i work for them). I'll swing by the store today and see about getting it warrantied.

This morning was fun, on the drive to work I noticed weird voltage swings and my headlights flickering at idle so I figured it would have a power failure when I turned it off, went to the dealer on the way to work, but the Z was behaving its best there. Once I got to work 10 minutes away, thats when she decided to fail. Got some video of it, thought I would share for the curious.

After turning off, I have zero power to anything, then the below happens.


A few minutes later this was the status of the car


Less than a minute from that video, car turns over just fine.

Just as a check in/resolution. Replaced the battery and no more problems (for now, I love this car but damn she hates me), old battery still tested fine, though the amps were a little below expected.

I noticed in your second video that the voltage gauge was reading about 9.5 volts. That leads me to believe it was the battery. Did you notice that?

So i know this thread is about 2 years old. I've been searching countless threads on all the big forums and using different keyword combinations through google search. This is nearly the same problem I have on my 2009 Touring. Did you ever find a solution? I'm getting pretty nervous considering I just purchased the car in October last year.

Thanks in advance,

- Chris

lol did you even read the thread? He stated that he replaced the battery literally two posts above yours.

I'm having an intermittent starting problem that may be related. Most times, the car (2011 370Z) starts fine, but sometimes I have to push the start button several times before it starts. The switch on the clutch pedal checked out OK, and the local Nissan shop found nothing else amiss. HQ technical support recommended replacement of the BCM (about $700), but the problem recurred. Now, the HQ tech wizards have diagnosed that a relay has gone bad, which will require replacement of the IPDM ($1,600).
After reading the previous posts, I checked my records and found that the problem started AFTER I had the battery replaced recently. I'll check the battery and post again if I find something amiss.