Brief history: Intermittent light would come on go off for past 30k miles. Finally stayed on. Checked codes (knock sensor and HP sensor) Reset light and immediately could not keep warm idle (went to zero!) Mechanic had same diagnoses, replaced both sensors AND solenoid. Idle is fine now and car runs great.

Here's the deal: If I turn the key and start it quickly (normally), the light comes back on! If I turn the ignition to "on" and wait ONE second and then start the car, the light does NOT come on.

Any ideas? The car is running strong (121,000 on the ODO), idles smoothly and still gets great gas mileage. Is there something wrong with the ECU or is it my ignition switch?

Thanks!!!