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Discussion Starter #1
Suddenly my MPG readout on the screen ( non NAV) went f rom giving accurate readings to 99MPG. Has anyone else experienced this?

Also, today I backed out of my garage and when I got to the bottom of the driveway it wouldn't go into drive or reverse...engine ran RPMs increased but no moving! I had it towed. It's been at the dealer all day and they keep trying it and it is fine.


Has anyone else experienced this?
 

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The two symptoms are probably not related, but I suppose anything is possible.

The fuel economy meter measures the amount of fuel being injected/pumped along with the reading from teh vehicle speed sensor to give an estimate of total fuel mileage.

As for the can't move condition, sounds like there was an issue with your transmission computer. I say this since the dealer has not reported a problem, and its likely some odd glitch caused your tranny to be unresponsive at that moment. I almost wished the dealer found something wrong with your car and replaced a part, but for now, you'll just have to keep a good memory of the exact conditions if it ever happens again. Make sure the dealer documents this case, so if your transmission fails outside of warranty you will have proof it was acting up when it was still in the warranty period.
 

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"The fuel economy meter measures the amount of fuel being injected/pumped along with the reading from teh vehicle speed sensor to give an estimate of total fuel mileage."

Do you really think this is how it is done? Fuel flow?

Homer
 

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I would assume the ECU has a means of metering precisely the amount of fuel the fuel injectors are flowing at any given moment, so why not use that for a mpg reading?

hfelknor said:
"The fuel economy meter measures the amount of fuel being injected/pumped along with the reading from teh vehicle speed sensor to give an estimate of total fuel mileage."

Do you really think this is how it is done? Fuel flow?

Homer
 

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I don't know.
Hence the question.

Older systems used Strain Gauges to weigh the gasoline in the tank I believe.
Strain Guages are extremely accurate sensors.
But they may also be "relatively" expensive and fuel flow may have replaced them.


Homer
 

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Consider:

Data from the ECU is used in the calculations shown by the MPG display.
Data from the ECU is used to control the inner workings of the transmission.


Looks like an indicated common point of failure to me...


An intermittent failure in ANY electronic component, especially the ECU, is extremely difficult to reproduce.
 
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