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Anyone had false readings from their OBC re. amount of miles left in the tank? Last weekend my OBC said 88 km's left. I can't swear to the needle's position but the yellow light was on. I was getting off the hwy. and my car started lunging nearly resulting in an accident and heart palpitations on my part. The car died a few miles later. I had my oil changed last week. Do you think they could've messed with the OBC by accident?
Thanks.
 

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OMGWTFBBQ
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The Range feature of the OBC is based on fuel milage over a previous period (not sure exaclty what it is) not current consumption. That leaves it very prone to error and it shouldn't be relied on.

I've said a number of times that the MPG (or metric equiv) feature on my car is quite optomistic, or the places where I buy gas are cheating me (or the odometer is just flat wrong).
 

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The range feature is an estimation based on a moving average of your fuel economy over the previous driving interval (seems to me that it is about 10 miles or so, but don't take that as gospel). Therefore, unless your present, instantanous consumption matches this average, the range indication will be of limited use.

HOWEVER, the average fuel economy (i.e. mileage) is a calculation for which the OBC can and should be very accurate -- down to the tenths of MPG. Mine is way off (says I'm getting an average of 32 MPG for a tank of gas, where I'm actually getting 23), and I keep getting the run-around at the dealer about calibrating it. Since the range calculations depend on the MPG calculation, my range feature is completely useless.

In MY99 and 00 E46 models consumption calculations could be adjusted through the instrument cluster test mode. This "test" entry (I think it is test #20) is no longer functional in MY01 and beyond. There must be some other way to adjust this, perhaps through the MODIC, to get this accurate.

If anyone has more info on this for late model E46's, please post!

Dave
 

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Double Bimmers
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It should be very accurate as you get close to 0 fuel.

Let's say you have one gallon in your tank... That OBC better say you have 15 to 30 miles to go. As you get less than one gallon, it better become even more accurate.

Anything outside a small range would indicate an error with the fuel level reading.
 

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OMGWTFBBQ
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CD-55 said:
It should be very accurate as you get close to 0 fuel.

Let's say you have one gallon in your tank... That OBC better say you have 15 to 30 miles to go. As you get less than one gallon, it better become even more accurate.

Anything outside a small range would indicate an error with the fuel level reading.
15-30 miles with one gallon is a pretty big spread. The same spread at 10 gallons would be 150-300 miles.

Running out of fuel with the OBC saying you still have 88km is something else.

I still don't get the wrong milage function, though. It knows how much gas I've used and how many miles I've gone. Why can't it divide properly?
 

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I've gotten down to 16.25 gallons needed to fill the tank. The range counter flipped to zero just before then.
 

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OMGWTFBBQ
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Nick325xiT 5spd said:
I've gotten down to 16.25 gallons needed to fill the tank. The range counter flipped to zero just before then.
In the 87 Corvette I had, the OBC range was apparently based on the 18 gallon "main" tank and did not include the two gallon "reserve" tank. I regularly did about 50 miles (DC to Baltimore or Balt to DC) when the range showed 0. At the end of those trips, it would usually take well over 19.5 gallons.
 
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