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Discussion Starter #1
I'm trying to figure out a strategy for determining if I have a potentially faulty fuel level sending unit OR the siphon pump is going. Yes, I searched and did a good deal of reading! How would you guys go about figuring out which is the culprit?

Symptoms:
- Test 14 shows codes 1) D7 81 248 2) BF 88 000
- Occasionally slow to read full tank on fill ups (xx gallon fillups!)
- Once went from near empty to 1/3 tank after restart
- Hear clicking sound from bottom rear of car after parking (siphon pumping back to left?)
- No peake codes

I haven't been stranded or anything, and my fill-ups are usually in the 16.X gallon range which leads me to believe the siphon pump IS working. I'll be driving around the next few days with the the fuel test on the dash to make sure the pump is keeping the left tank empty.

- What other steps, tests, or checks would you guys make?
- I've read the excellent fuel pump DIY, is there a DIY for the sending unit on the left tank? Or for the siphon pump?

Thanks in advance!
 

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D7 on Test 14 is a telltale for a left level sensor failure. You should see weird fluctuation on Test 6 with a D7.

Test 6 shows tank levels. If your siphon is broken, then the left tank will not read 0, when the total is <31L.

As long as you are willing to ignore the accuracy of your fuel gauge, in favor of some alternative tracking e.g. trip odometer, a D7 won't strand you.
 

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Ran around town with test 06 up last night. Started with even figures across left and right tanks then watched the left number go crazy. At a stop it would read some thing like 20/30/50, but on the go I'd see readings varying from 15-34L in the left tank. Definitely sounds like the sending unit!

Ordered a replacement sender and the seal last night will knock this one out next week. Thanks for the advice.
 

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Ran around town with test 06 up last night. Started with even figures across left and right tanks then watched the left number go crazy. At a stop it would read some thing like 20/30/50, but on the go I'd see readings varying from 15-34L in the left tank. Definitely sounds like the sending unit!

Ordered a replacement sender and the seal last night will knock this one out next week. Thanks for the advice.
The numbers will fluctuate a bit as fuel sloshes around. If you hit the button one more time, it goes into a smoothing mode, where the number you see is relatively constant.

Regards,
Jerry
 

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Discussion Starter #5
The numbers will fluctuate a bit as fuel sloshes around. If you hit the button one more time, it goes into a smoothing mode, where the number you see is relatively constant.

Regards,
Jerry
I'll give that a try today and see what it does. I know I have a problem somewhere given the code and occasional gauge issue, hoping the sender replacement fixes it.
 

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I was really very curious about this coming from a car with only one tank. The learn is excellent. I am also trying to learn more about the test 14, The list of codes I have is a little sketchy. My list says D7 is "inaccurate on empty". So I am guessing that is not right or you guys would not be having this conversation. Could you direct me to the most accurate list. There are so many lists on the board with different info I don't know which one to believe.
 

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While there is a list here that purports to explain some of the codes on the OBC, it's not definitive. The takeaway is that the last set of numbers in a line is a counter. If that number is not "000" then a problem is current/recent.
 

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Discussion Starter #8
@Sailor - confusion around the test 14 codes is one of the reasons I started this thread. I was looking for insight on the D7 81 code being indicative of A) the fuel level sender unit or B) the siphon pump being bad. Searching shows mixed opinions on this which is a bit frustrating.

I replaced the left level sensor yesterday, very straightforward, it follows the fuel pump DIY almost exactly with the obvious exception of the fuel pump not being involved! You do have to reconnect the siphon pump. The perforated ring of leather matting around the access port was already loose, so someone has been in there before.

At this point I'll just keep an eye on the XXX counter on the end of the D7 81 code on test 14 and see if it keeps decrementing down to zero. If it resets to 250 or whatever the high mark is perhaps I'll replace the siphon pump too, though it seems to be working fine.
 

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If I understand the counter # gets smaller if the code is not reactivated. Countdown timer to good running. The first number is the code and the second number is still unconfirmed. I have read some more on the topic and there seems to be some conflicting info. I would be curious to know how long it takes for your counter to decrease. There was something less sophisticated with E34 that we never understood correctly, but were guessing was related to number of starts. I had 3 entries on my car when I first looked but as I went through each system on my car and cleared the codes they also cleared. I wish I had of written them down. I was unaware I was clearing them from test 14. I guess I should just be happy I only have 0s.
Thanks for the info you guys have given me a much clearer understanding than any of the posts I have read.
 

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Discussion Starter #10
@Sailor - your understanding sounds correct to me, I can verify the last number decreases by one every time I start the car (assuming the error isn't retripped, in which case it resets to the upper bound which I think is 250). I have one other error that has "zeroed" out, the BF 88.

I wish there was a way to flush the codes without going to the dealer. Also hard to believe no one has more definitive information on these codes, I guess BMW has ninjas on staff to take out anyone who leaks the key.
 

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I just have a genesis scanner. It is not a toy by any means but it is no GT1. I cleared mine just by clearing the codes in the specific area. I would imagine that any place that has a scanner with compatible software could clear them. You would just need to know what area the BF is from, but the D7 would clear from the central body module. It is not just the Test 14 that has codes. I can read every BMW code but the company that makes my machine does not have access to the definitions, nor can I find them. I get "description unavailable"more times than I like. The DSC and Park distance are the worst as neither have any descriptions. The code alone seems to be more useless than not knowing at all.

Thanks again
 
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