Hello my friends gmc envoy was not starting i went to diagnose trouble codes i saw the engine check light on when i attached the device i didnt read any codes from the ecu saying there is no trouble code i asked him to unplug the throttle position sensor wire as he unpluged the wire one mor engine check light appeared on the dashboard it was a bit digger in size than the normal engine check light with arrow facing downwards.why is there two engine check light wats the reason. why it cant be diagnosed throught the obd2 reader i am using elm327 ver 1.3a with scanxl.

there r two engine check lights what a re they how to diagnose it please help me out tell mr the functions of both engine check lights 1. normal engine check light (can't diagnose with my)device)
2. engine check light with arrow facing downwards.
thanks in advance