E70 Voltage issue
 

I was attempting to jump an 07’ 4.8 I had my code reader hooked up at the time as I wanted to see if there were any pre-existing codes in the modules. I noticed with the jumpers hooked up and electrical donar vehicle running all I was seeing on my code reader as far as voltage was sub 12 volts 11.65 to be exact. I was surprised I didn’t see 13.5 plus. I jumped using the terminals under the hood. As I did not have a volt meter with me I was unable to confirm how much current was getting to the battery. Although after looking at the electrical diagram I don’t see any reason there shouldn’t be the 13 plus volts getting to the battery. Any reason there wouldn’t be 13 or so volts seen at or by the DME? I did check connections at the battery and connections tight and clean. I did attempt a start but engine turned over very slowly no start. Thinking IBS or poor ground perhaps? Thank you for any guidance.

Yes I agree this is strange. Well that said I bought it and will be reporting back with my findings.

Sub 12 volts I don't think is uncommon before startup. However, at least 13v is important to achieve once the vehicle is started. Im guessing maybe the donar vehicle has a smaller battery, no?

It was another X5 E53 to be exact so another group 49 battery. I don't think the alternator is coming on line as I was able to start but only runs for 3-5 seconds before shutting down and lots of error codes.. This is a new vehicle to us and has sat for over a year. I finally have it in my car port so will get a better chance to check fuses, connections etc. Will report as I go through the systems. Thank you

Today I was able to confirm for the 5 seconds the car would run the alternator was not charging. Now onto finding out whats at fault, alternator or DME.. Lots of codes thrown after the 5 second run. One of the more notable was - Alternator not seen. Voltage regulator??

pull the alternator and replace the voltage regulator piece. mine works great now. prior to this we threw codes and transmission went i to limp mode.

I agree. I just ordered one.

Also going to pickup a pair of the Blue relays for the DME. I don't mid spares..

What is so special about the blue relays? And speaking about dme relays, which are responsible for the communication with the valvetronic computer?

DME relays were/are a known failure point, especially for my old Porsche. Just though I would cover off another potential culprit. The relays are blue in colour and located by the DME. DME talks to quit a few components so keeping a close eye on the thing. Spent quite a bit of time today checking all the fuses (Got to love the front fuse box..) All fuses were good. My BIG concern is this thing sat for well over a year and owner reports it running when parked due to rear bags collapsed and pump not operational (Confirmed pump not working and main 40A fuse blows - Looking for a replacement ;) so somewhere over that time something went off the rails. I guess its possible the regulator could have gone faulty over that time frame. Or that was another reason it was parked.

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Well I'm here to wrap this up. In doing my diagnostic checking fuses, looking for any rodent damage to wiring harness etc. I happen to glance at the fuel pump relay for the third time. In looking at so many bloody electrical connections and relays I noticed it didn't look like a BMW relay. I pulled the thing and sure enough it was a generic relay. I went over to my box of BMW relays and installed the proper green relay and BINGO!!!! all was good and ran great especially for sitting for so long. Interesting how this relay could cause so many unrelated and serious codes appear.
End of the day I have become very proficient in checking fuse boxes and electrical connections. Now onto the air suspension compressor. Thanks for all the support!

- This was a copy and paste from my first post (Wish Me Luck) Wanted to wrap this up. I happen to have a brand new Valeo 220A regulator sitting around LOL

Couldnt let this go unacknowledged!

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