Is the a18 pin on obd2b that is "MIL" Malfunction Indiciator Light the Check Engine Light...can i wire an LED to that pin if i remove and make a custom gauge bezel?

What about the low Fuel Indicator, is it possible to wire up an LED to replace the light that is in the factory bezel?

 

yes for both

but you may end up with the CEL LED being partially on at all times.
the driver for the CEL light requires a little current to be pulled to turn the driver off. This normally isn't a problem with a bulb since it takes more current than that to turn it on. (that's a general explination, it's more complicated than that)
What I did was wire up a LED in the spot that the CEL is, but jumper to a bulb in a spot of the cluster that's blocked off. ECU sees a bulb, I see the response time of a LED.

 

Im not using any of the factory cluster at all. So i may have to deal with partially lit, maybe i can dim it with some clear tinted paint.

What about the Low fuel light, where would that wire in?

i dont have to use an LED if there is a nice bulb i can get.

 

u will need to put a relay in the wire for the MIL. when no CEL is present, the output on the ecu sends +12V all the time. when u have a CEL it sends 0V. im guess the stock harness has a relay before it hits the cluster.

i did the same thing with a LED on my old car and i went ot school for Electrical engineering so i just made a circuit to invert the output at the ecu. Relay would be a quicker easier way.

As for the fuel, u will need to make some type of circuitry to monitor the resistance in the fuel level sensor and have it trip a light according to the resistance in the stock sender unit

 

Radio shack sells 12V LED's, thats what i used.

 

it's called active ground. the constant side of the Bulb (or LED) is wired to 12V, the signal from the ECU provides the ground. This is more than common practice these days in automotive applications.
There is no need for a relay to delay the turn on of the CEL (especially problematic for counting short flashes of DTCs), or any special circuitry to invert the output. Only a small load to make sure that the output doesn't turn on the LED prematurly.

OP: I will try to measure the current draw across the bulb and give you a radioshack part to install in the next few days. (provided we're not under a few feet of snow by then)

96+ civics and tegs have a switch built into the fuel tank sender that runs the stock light. It should work fine with a LED.


OP: what sort of custom cluster are you creating, minimalistic for race purposes or simply all out custom for some other reason?