check engine light comes on when under steady load but when I stop and blip the throttle it goes away

 

First thing to check is that the battery connections are good and that it's charging ok.Plus wouldn't hurt to load test the battery to make sure it's taking the charge.Don't even trust a new one as they can be faulty straight out of the box. That could trigger the check engine light sometimes instead of the battery light.Plus make sure you hear the fan cycle on and off. Several things that can trigger the check engine light.You can also cycle the key on and off 3 times,leave the key on and see if any blink codes come up that can narrow down what's happening.