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Old 07-08-2009, 11:08 AM
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bluebee bluebee is offline
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Location: San Jose, California
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Mein Auto: 02 BMW 525i M54 auto 130K
Where (else) does the E39 obtain mileage information?

Originally Posted by 540iman View Post
I do not believe the fuel gauge is tied to the ABS module per se', but the fuel useage system is. I believe it is the fuel remaining calc. that gets so jacked up by levels being sent from the fuel gauge, but no input that mileage is being put on the vehicle but fuel is being consumed with no speed sensor output.
That makes sense that the fuel-usage system needs to know the mileage, and, since the mileage comes from the left rear wheel sensor, that the fuel-usage system gets "jacked" up.

But the fuel-remaining gauge is just a potentiometer, right? It should just show the level of fuel, no matter the mileage (otherwise emptying or filling the tank with fuel would screw it up).

Anyway, I do understand that the fuel-usage system may need the left rear wheel sensor so maybe that's what everyone is talking about when they (erroneously?) say the fuel gauge started acting erratically when they removed their ABS module.

The reason I care is that I'm trying to write a definitive DIY for troubleshooting, taking into account everyone's input (including a LOT of yours 540iman!) ... and ... well ... the erratic fuel-gauge reports don't seem to fit my model of what is going on.

While the ABS module is off the car for rebuild, another good point you brought out in your related post was "your odometer and your internal mileage tracking will disagree the longer you have no odometer. I do not know how far the two can differ before you throw a code that you may have a real hassle resolving."

I wonder if anyone has more details on this potential problem of conflicting mileage with the ABS module removed?

- Other than the left-rear wheel speed sensor, where else does the E39 obtain mileage information (which would be out of whack)?
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