Won't run without battery connected...

[onebad7up]

My wife called me this morning at 5:00AM to tell me that she was broke down on the side of the road....perfect start to a Monday morning.

After driving for 10 minutes, the warning indicators for all of the various systems started to flash (ABS, AWD, Transmission, etc.). She pulled over and the truck finally shut off on its own.

I was able to hook up a helper battery and it would start and drive. I pulled it over to a parking lot and pulled the codes. P110F, P115D, P1890 and P1551. It looks like these are random codes so they likely came on because of the low voltage condition. No way all these different items failed at once.

When the truck was running I tried to disconnect the battery terminal in order to check the alternator. The vehicle died immediately.

This leads me to think it is a bad alternator, but I just had it checked at recently after installing a new battery.

Does anyone know how I can verify that it is an alternator and maybe not something like the voltage regulator?

[Doug Huffman]

BMW cautions not to disconnect a battery for troubleshooting. The charging and power distribution systems are like nothing with which you are familiar.

E70 Training and General BMW Training.

https://drive.google.com/folderview?...&usp=drive_web

https://drive.google.com/folderview?...&usp=drive_web

[jfoj]

You DO NOT disconnect the battery while the engine is running on modern vehicles. You can cause a LOT of problems.

Get a Voltmeter or use the Hidden OBC Menu to verify the running Voltage.

Also keep in mind the E70 and probably other similar platforms have a VERY POOR method to notify the driver there is a charging problem. I really do not think the E70 can notify the driver!!

http://www.scoopz.com/m5board/E60_Hi...structions.pdf

I run a wire UltraGauge on my X5 with threshold alarms for Temperature and Voltage.

UltraGauge OBDII Scan tool & Information Center

Low Voltage an any modern vehicle will cause ALL sorts of crazy problems.

[onebad7up]

Originally Posted by jfoj

You DO NOT disconnect the battery while the engine is running on modern vehicles. You can cause a LOT of problems.

Get a Voltmeter or use the Hidden OBC Menu to verify the running Voltage.

Also keep in mind the E70 and probably other similar platforms have a VERY POOR method to notify the driver there is a charging problem. I really do not think the E70 can notify the driver!!

http://www.scoopz.com/m5board/E60_Hi...structions.pdf

I run a wire UltraGauge on my X5 with threshold alarms for Temperature and Voltage.

UltraGauge OBDII Scan tool & Information Center

Low Voltage an any modern vehicle will cause ALL sorts of crazy problems.

The hidden OBC menu looks complex so I would prefer to stick with the voltmeter for now.

I just dropped the battery off at batteries plus for a recharge. I charged it on 2amp for 1 hour before taking it over. Their readings were 12.03V w/ 756 CCA of a 850 CCA rating.

[onebad7up]

Originally Posted by Doug Huffman

BMW cautions not to disconnect a battery for troubleshooting. The charging and power distribution systems are like nothing with which you are familiar.

E70 Training and General BMW Training.

https://drive.google.com/folderview?...&usp=drive_web

https://drive.google.com/folderview?...&usp=drive_web

Thanks for the info. I will read through them and find the files associated with the electrical system.

[jfoj]

12.03 Volts is LOW. I put my X5 on a maintenance charge about once a month.

[onebad7up]

I am leaning towards the alternator. 125k miles, I had it off recently whenever I replaced the oil thermostat housing seals. It is possible that one of the connections loosened, but I won't know more until I get it home.

Disconnecting the battery and dying is not a good sign.

[A B Able Truck]

Originally Posted by jfoj

12.03 Volts is LOW. I put my X5 on a maintenance charge about once a month.

A good idea, especially for the short commute driver.

What Causes Car Batteries to Fail? – Battery University

***

[Doug Huffman]

Originally Posted by A B Able Truck

A good idea, especially for the short commute driver.

What Causes Car Batteries to Fail? – Battery University

***

Thanks for the citation link URL. I thought that I had read every page at Battery University, but not that one I discovered.

[Davidf]

...not to mentioned disconnecting the battery can damage the diodes in the alternator. If it wasn't bad before, it probably is now. I vaguely recall my E38 behaving as you described when the battery developed an internal short. With all that said, you would expect an engine to stay running even with a faulty battery (i.e. alternator is outputting). But, the electronics in these cars (i.e power management) can cause unexpected results/situations.