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1994 Cutlass Supreme DIS MPG not working


IrvineADL
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Hello, Long long long long time reader of the forums here. Using the information I got from here, I managed to wire in a Driver Information System into my 1994 Olds Cutlass Supreme. The DIS powers on and most of the functions work, HOWEVER I cannot get the average or instant MPG to work. The DIS always says 80 average MPG which as much as I would like to believe I know it's simply not true. Fuel Range is stuck at reading about 79 miles and the fuel used function does not work. This DIS is from a late 80s Ninety-Eight. The coolant temp, tach, battery voltage, date and clock all work fine. Also the trip computer is hilariously inaccurate. Anyways does anyone have any thoughts? Can I get the MPG to work? Isn't there some sort of fancy chip that can be used to make it work? If it matters at all, I also have a DIS from a cutlass calais  

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The 94-95 are obd 1.5 and don't send the same signals. I had a chip made by Shawn about ten years ago to make those functions work. I still have it and I'd be willing to part with it. Shoot me a pm.

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the 98 DIS will be slightly off for a few items(mostly the overall fuel range), but it will work with the revised calibration. if you have a 3100 powered car, I do have an experimental patch, but I haven't tested it in a real-world vehicle yet. I need to get on that sooner rather than later.

 

I'm curious what you'll find when you put the DIS into diagnostic mode(press DEST, then RESET, then a distance of 8192 miles), a lot of DIS have been swapped around, you could have a unit originally from a Cutlass Ciera or Calais or even a correct CS unit.

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This concept eludes me, if it has that math for the correct engine, and it's seeing uart serial data and a proper 4kppm vss it should work.

Of course I understand that's not always the case but it doesn't make sense.

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This concept eludes me, if it has that math for the correct engine, and it's seeing uart serial data and a proper 4kppm vss it should work.

Of course I understand that's not always the case but it doesn't make sense.

I think it has something to do with sending a different type of signal or something, or in a different format. At least that's kinda how I understood it

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This concept eludes me, if it has that math for the correct engine, and it's seeing uart serial data and a proper 4kppm vss it should work.

Of course I understand that's not always the case but it doesn't make sense.

GM changed some of the serial data sent to the DIS for 94-95 compared to 88-93, just like how the 96 GP DIC is different from 94-95. it isn't too different and is the same number of bytes sent and on the same schedule even, but mostly a slight rearrangement.

 

 

The one I have is for an LQ1, he has a 3100. Anyone know if it'd be decently accurate? I know Shawn had done some math with the flow or something. Maybe he can chime in

 

wouldn't work... you're talking a flash PCM vs a MEMCAL based unit. would have to upload a new calibration over the ALDL port(or do it the hard way and desolder the PROMs, rewrite them in a standalone burner and solder them back in, but that's overkill).

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Robert, that would be great, and It sounds like you are fairly confident that it will work. How would I install it? And I did a diagnostic test and here are the results: E MC L 00 21 4 H. VERSION 2.2 CH 

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definitely came from an 88/98, one with an analog cluster(or at least a base digital unit) and it thinks you have a 21% full tank of fuel(with an assumed full capacity of 18 gallons due to it being meant for a C/H car).

 

i'll need to perform a final bench test before I'm certain of it functioning as intended, but I can probably arrange for that in a few days. it would have to be done via a calibration flash, so you would either need to send your PCM to me for an update(car wouldn't be drivable until the PCM is reinstalled), acquire another PCM(any 16196397 PCM would work(every 94-95 3100 car except for the a-bodies), though some 94-95 3.4 f-bodies used it as well, different knock filter though, would have to be swapped from yours) and send it to me, have me acquire another PCM and send it to you after changing the calibration or go the DIY route and build/buy an ALDL cable and acquire one of the two currently available flashing programs with this PCM.

 

there are versions of that PCM on ebay now for far lower prices than what any salvage yard I've ever been to will sell them for. the last one I bought from ebay cost me $13/shipped from California, but I'm not willing to part with it, i have a lot of prototyping to do with it once i open it up.

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Alright that sounds good I'll let you know when I get another PCM. I should note though that my car has some electrical gremlins, and by that I mean that every PCM I've installed in it has thrown a check engine light with a BAD ECM code at me. The weird thing is that the car runs perfectly fine. Anyways that's a whole other can of worms. And yeah why does the DIS think that I have 21% fuel? I know this must be intertwined with the MPG issue but I have no idea how or where the DIS is getting that false info from 

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the DIS samples the fuel level signal that is created by the cluster/fuel level sender.

 

is the actual fuel level not close to 21%? there are some settings you can change in the DIS by having a circuit grounded or not grounded.

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