1993 Plymouth Voyager Electrical

I have a gremlin in my electrical system. While driving the battery light came on, so in my mind to me that means either the battery is malfunctioning or the alternator. So I had both of them check, both of them passed the test. For personal reasons I put in a battery with more cranking amps than a direct replacement battery. Gremlin still remains, here's the kicker I drove 20 minutes with the headlights on and the battery light, check engine light, and the check gauges lights on. I get home turn the engine off, sat for 30 seconds, turn the van back on and the battery light is off and the check gauges light is off but the check engine light is still on. What in the world is that?