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My 2 DICs Don't Work the Same - I Wonder Why?

sparkydog

sparkydog

New member
Heh - I made a funny thread title.

So I just sold my 2000 GT and now I'm driving a 2001 GTP. Both cars have fuel level sender problems where they read lower than real world. So I just got in the habit of running my DIC in "gallons used" mode. That way, when the fuel sender and gage went into false "low fuel" mode - I knew how many gallons I really had left.

On my 2000 GT, the fuel used mode was amazingly accurate. When I would fill up the pump amount and the DIC display amount were always no more than 1/10th of a gallon off from each other.

But on the 2001 GTP, the DIC is always about 1 gallon lower than what I pump back in. Which is a large enough amount that I could possibly get myself in trouble and run out of gas.

I assume that the DIC computer is using some kind of calculation to come up with how much fuel is used - not based off of the faulty sending unit but probably the ECU and injector pulses and miles or something.

Does anyone know how the fuel used is calculated and why it would be off by 1 gallon after about 10 gallons are used?
 


Mine is the opposite.. a gallon heavy so I never really worried about it. It would be good to know how the car computes to the dic.

Good question

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I came up with a possible answer to my own question. If I remember correctly, when I bought the GTP a few years ago, the DIC was broken. So I went to the junkyard and replaced it. But maybe the DIC from the junkyard was not from a GTP. So perhaps there's a chip in the non GTP DIC that thinks it's in a car with smaller fuel injectors (for an L36) than the fuel injectors on the L67? If so, then it's calculating fuel consumption based on L36 squirts instead of L67?
 
IIRC the pcm feeds the DIC most of it's fuel related info.

The true fix here is to say.. close enough is good enough. That's just how these senders/gauges are setup. The fuel tank isn't a perfect squared out tank, the sender doesn't compensate for tank shape, and at best it's a good reference not an exact measurement.
 
I think I know how/why the DIC fuel consumed was 1 gal off of real world. This GTP was driven by my daughter for about 3 years and she probably never reset the MPG portion of the DIC. She was probably getting better gas mileage then I did once I started hot-footing around after I reclaimed the vehicle from her. Once I read the owners manual I discovered the DIC uses the MPG calc to also calc the fuel consumed. So I realized I should try resetting BOTH the fuel consumed AND the MPG values during a gas station fill-up.

At the next fill-up after that, my real world gas consumed and DIC gas consumed values were within 1/10th of a gallon.
 


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