Thanks for the replies as they're greatly appreciated! I must say, now that I have battery 101 down thanks to the great clarification/breakdown by Qsilver7. I didn't know there were so limited manufactures producing the same thing with different labels on them.

As for the alternator, I too am skeptical that the Bosch reman, even though is supposed to be superior to other might be spiking / dropping voltage for a split second. Upon unlocking the cluster though, it seems to hold steady around 13.5V +/- 0.1V. I took the car to my Indy for a quick diagnose and for him to read the codes the other day. Upon connecting it to the computer, there were 27 codes.. most were nonsense held in the memory form the past but he said there were three that were serious... If I remember correctly, CAN Communication error, Transmission Control module communication error, and another DME communication error.

He wiped the codes, restarted the car and sure enough within a few seconds the Christmas tree of lights in the dash came on again, gauges stopped working and temp gauge went to red. He basically said it looks like something more serious and that he'd need to spend a lot more time into looking at the cause of the errors. Dropped off the car this morning so I'll update this post on what his findings / corrective actions were. BTW - He showed me the transmission forward drum from another E53 owner who had driven ignoring the Trans Failsafe error. He said that basically due to lack of hydraulic pressure, the metal drum started to crack and the whole transmission had to be rebuilt. I've been super gentle w/ it during this time and only driven it if I had to, but needless to say it got my attention.

On a side note most likely not related to this issue but who knows really... , one of the error codes was for the thermostat. Now, I know that I had a brand new one replaced when I did the water pump about 20K miles ago, but I don't understand what could be causing it. The mechanic said your fuel consumption with go down the drain since the car thinks it's colder than it really is and will dump more fuel. My OBC says I average about 11.7MPG in normal mixed city / freeway driving. Does that sound about right? Probably meant for another thread but if anyone has a quick answer, I'd appreciate it.

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Say what you will, nothing drives like a BMW.


2003 X5 E53 4.4
2001 740iL Sport
1990 325i E30 - Restored/Restoring