Crown Victoria Digital Dash

Just purchased a used 1992 Crown Vic LX in good condition, which I'm pretty impressed with, except for the Digital Dash. For one, when you fill it up,
it gives you a CO in the right cluster and the fuel guage has two dashes at the top and two at the bottom. The owners manual says this is an "error" code and to take it to the dealer. The previous owner says he had the fuel pump/gas guage assembly replaced and it did the same thing. Obviously, I don't want to redo that again if it won't help. Does anyone know if this is a digital dash problem, a onboard computer problem or ??? Thanks for any help. Rod
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Are you leaving the engine running while you fill it? I wonder if this is anything like GM's "Your gas cap is not on tightly enough" trouble code. All one gets in the check engine light, great for those of us that live in rural Alaska and the local mechanic goes moose hunting for 3 weeks the day before this happens... I drove 200 miles round-trip to get told the wife limp-wristed the stupid cap.....
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CO means Circuit Open. Very likely, the sending unit in the tank has a dead spot near the top and when it's full, it doesn't send a signal. If you had a mechanical dash, the guage would peg at one extreme or the other.
Do you "top off" the tank after the pump shuts off? I just wonder if it happens when the tank is full to the shut-off...? When it returns to normal, how full does it show?
PoD

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rodg wrote:

CO = Circuit Open. This usually means a bad connection at the sending unit, or a bad ground in the wiring for that circuit.
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rodg wrote:

"Circuit Open"
It's a sending unit problem, nothing wrong with the display. Ignore it if you have a good idea of how much fuel you have on board, or if it works OK when it comes off full.
Rob
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I agree - ignore it if it is OK after it's off full.
PoD

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Thanks for the feedback. It isn't gas cap. Doesn't make a difference if I top it off or not. It doesn't seem like the guage is accurate either once tank starts to empty either, so for right now, I just set the trip odometer at zero when I fill and refill at 250-300 miles. thanks Rod
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rodg wrote:

CO = Circuit Open This is usually caused by a bad connection, ground or even a break somewhere in the sender wire.
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There is either a poor connection between the sending unit in the tank or the sending unit itself is bad. I do not think there is a problem with the digital dash itself. Personally, I think the digital dash may be a bit more reliable than a mechanical one but I may have just had good luch with the three I've had. Since the in-tank assembly was relpaced with no change, look for bad wiring. There is a whole troubleshooting proceedure in the Ford shop manual to determine the cause of a "CO" indication. A Ford dealer can probably fix it - or you could buy a Ford Shop Manual (don't get a generic one, it won't have the info you need). Manuals in paper or on CD are sometimes on Ebay...
PoD

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