Originally Posted by 1_Hot_Legend_LS
One thing to add:
With the ignition switch in the on position both the Check Engine MIL and the D4 (on Auto models) should come on for 3-5 seconds then go out. If the Check Engine MIL Stays on and the D4 light does not come on at all, the main relay is faulty.
This is what has been happening to my old 93 LS ( I sold it yesterday with a BHG and apparently a faulty relay ) but by turning the key from Accessory 1 to On repeatedly the D4 light will eventually light up and presto the car fires right up.