M35 Instantly Dead (electrically)

[07M3.5]

I am hoping someone on the board has some ideas as my dealer hasn't seen this issue before. The electrically dead (zero power - like battery cable cut) condition occurred when the start button as pressed yesterday morning after the car had been parked overnigh night. Prior to attempting to start the car, I had opened the trunk and the interior lights had been normal when entering the vehicle. Upon pressing the start button, the start light blinked once and then all went dark (so to speak). The car never made an attempt to crank the engine. The trunk would not open, all interior lights were off, etc.

After arranging for AAA, I decided to check the battery, opened the hood and battery compartment (battery was replaced in 2011). Voltmeter showed 12.5 volts and connections were solid. As I was prepping the car to be towed, I noticed that the interior lights were now back on. I pushed the start button and the car instantly started as normal.

The clock had lost 35 minutes; the steering wheel had lost its memory postion; the trip odometers had reset to 0; the climate contol system had turned itself off; however the radio presets were still set correctly. There was no check engine or adverse indicators on the instrument cluster. The dealer found no faults in the computer.

The dealer still has the car. I am hoping that this unsettling issue can be attributed to some specific fault and fixed. Many thanks in advance for any ideas....

[Larz]

Sorry to hear about that. Let's hope it turns out to be something simple like a conneciton that is not quite secure or some other easy fix. I suppose you have already thought about or have indeed left the car at the dealer overnight so they can try a cold start-up tomorrow morning. Maybe the situation will repeat and they can locate the issue while it's actually happening.
Please leave an update when the final word comes down.

[merlinq2]

body control module, look it up, it is connected to the imobilizer etc. I was told when those fail the car is dead

[cruzad3r]

i'm thinking battery and connections issue. if it's anything else, the car will not start at all.

[SteveTheTech]

i'm thinking battery and connections issue. if it's anything else, the car will not start at all.

You would honestly be surprised the things I see happen even with mostly tight cables. If you can move one at all it is too loose. It would make sense that as you command more power an incomplete ground would facilitate a complete lack of response but yet have over 12 volts of static charge.

I see most problems with the yellow Wallyworld batteries, and Optimas (oddly enough). They sometimes have negative terminals that are a fraction of a hair smaller than the original, so when the nut bottoms out many people think the terminal is tight but it may not be tight enough.

[splix]

I had the same thing happen. Clean your battery terminal connectors.

[07M3.5]

Thanks everyone for your observations and suggestions.

The dealer kept the vehicle overnight to do a battery stress test and had two technicians look at the issue. The second tech determined that the positive battery terminal was "loose". The dealer had replaced the battery in 2011 and "apparently" not tightened the terminals sufficiently. Anyway we are counting on that rational to explain the event.

It is clear from both the dealer and folks here on the board that there isn't any reason to be concerned that this issue will reoccur. Again, may thanks and we can all continue to enjoy our Infinity M series vehicles!