Instruments/Fuel System - Distance To Empty Display Info
17 Distance to empty display in on-board computer: General Information
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2028440/1
January 20, 2012.
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Affected Vehicles
Condition
Customer statement:
^ After refueling, a different "distance to empty" (vehicle range) is shown than last time the fuel tank was filled.
^ The vehicle range display drops inconsistently.
^ After refueling, the vehicle range display does not change for a long period of time.
^ When driving on hilly roads for a long time the vehicle range display suddenly changes significantly.
There are no DTCs in J285 (address word 17) related to fuel senders.
This condition does not involve or affect the accuracy of the fuel level indicator, but only the estimated distance to empty display on the on-board
computer.
Technical Background
The primary purpose for the range display is to prevent the vehicle from running out of fuel, meaning well before the tank is totally empty a warning
will be given and the range may show 0 miles. The warning (acoustic warning and fuel low indicator) is provided as soon as the fuel gauge needle
enters the red zone.
The average and instant consumption figures shown in the on-board computer are not used for calculating the range. The range is calculated using an
internal, weighted value instead. Two different calculation methods (filter algorithms) are used for determining the range display:
1) Vehicles before model year 2009:
Audi A3 (8P), A4 (8E), A6 (4F) up to model year 2008, A8 (4E), Audi Q7 (4L) up to model year 2008, TT (8J) and all predecessors:
Only consumption figures of the last 50 kilometers (31 miles) are included, whereby the last kilometer has the highest weighting and the first the
lowest.
If the driver drives efficiently right before he refuels the vehicle, this can cause the vehicle range display to be noticeably higher than the previous
fill-up. Conversely, an aggressive driving style can cause the fuel range display to be lower than previous.
2) Vehicles from model year 2009:
Audi A4 (8K), A5 (8T), A6 (4F) from model year 2009, A6 (4G), A7 (4G), A8 (4H), Audi Q5 (8R), Audi Q7 (4L) from model year 2009 and all
successors.
A gradual driving profile is built from the last 50 kilometers (31 miles) and 500 kilometers (310 miles): The short-term consumption figures over the
last 50 kilometers (31 miles) and the long-term figures over 500 kilometers (310 miles) are included in the calculation, which is also based on the
tank volume.
With this method the range display can only rise when driving efficiently for extended periods, resulting in a more realistic "expected" fuel range.
Tip: With both methods the range display after filling up depends on the driving style before filling up. This means the range displayed after fill-up
will not be the same in all cases. In addition, the remaining range display does not refer to the whole tank volume. It only indicates a trend based on
the short to medium-term fuel consumption.
Production Solution
Not Applicable.
Service
Explain the operation to the customer.
Warranty
This TSB is informational only and not applicable to any Audi warranty.
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Additional Information
All parts and service references provided in this TSB are subject to change and/or removal. Always check with your Parts Department and service
manuals for the latest information.
