Has anyone ever replaced their check engine light with an LED?

I've replaced all of my "idiot lights" with these (well, aside from the battery light, since I thought it may benefit from being able light dimly in case the voltage is flickering)
http://www.superbrightleds.com/cgi-b...2F74-xHP3.html


And what I've found is that the CEL turns on very brightly when the ignition is first turned on (idiot light "test mode"), then dims a bit as I hear a relay click. Then when I start the engine it stays dimly lit all the time. I don't have any issues with a regular bulb, the light works normally.

This is in my CRX with a P28 OBD1 ECU (that's why I'm posting it here, since the Civic EG ECU is running the CEL in my cluster). The ROM on it was built using CROME, and I have the CEL shift light code setup in the BIN.

Anyone have a similar experience or any information that might be helpful?

I have to assume that the ECU is expecting some sort of load on that light.

 

The CEL receives constant voltage. The CEL turns on when the ECU supplies ground for the voltage.

My guess:
The ECU supplies a small amount of ground to the CEL even when the CEL is normally off. This small amount of ground is insufficient to illuminate an incandescent bulb but is able to illuminate the more sensitive LED.

 

have to checked to make sure you don't have any codes?

Ron's guess makes the most sense....