Figure out why the CEL doesnt work, go from there. Do you recall it ever working? Should have always come on with key to run, flashed once, then stayed on until the engine was started.
It could be as simple as a loose wire to or from the CEL, but it could be indicative of something else. IIRC the ECM grounds the CEL to light it, so it could be a ground or other wire/connector issue.