What does this mean when engine light with down arrow and loses power

Go to autozone or similar and have it scanned for free the dealer would charge you about $60 bucks . Probably just a sensor or a simple fix.

Replace you throttle pisition sensor
You don't want get to far afeild this sensor moves a lot ever time you touch the gas pedel its made of plastic and it a huge ware part .And can be tested with an ohm's meter .
Works like the volume knob on a radio the more its open the louder it gets .The problem is flat spots as you turn it you get nothing in some spots and works in others it has to be even all the way through the cycle .You also need an anilog meter digatial meters won't work on this test.

REDUCED ENGINE POWER: Refer to Engine Control Module Description.
Reduced Engine Power Mode
When the PCM detects a problem with the throttle actuator control (TAC) system the PCM enters one of the following Reduced Engine Power Modes:
• Acceleration Limiting--The control module will continue to use the accelerator pedal for throttle control, however the vehicle acceleration is limited.
• Limited Throttle Mode--The control module will continue to use the accelerator pedal for throttle control, however the maximum throttle opening is limited.
• Throttle Default Mode--The control module will turn off the throttle actuator.
• Forced Idle Mode--The control module will perform the following actions:
- Limit engine speed to idle by positioning throttle position, or by controlling fuel and spark if throttle is turned off.
- Ignore accelerator pedal input.
• Engine Shutdown Mode--The control module will disable fuel and de-energize the throttle actuator.
There are DTC'S -diagnostic trouble codes stored in the PCM , could have throttle position sensor , or gas pedal position sensors .Time for a visit to the dealer !

I am only able to shoot you a guess on this and hopefully it steers you the right direction. I believe your vehicle went into limp mode. This can be from over heating to emission problems to a bad piston. The vehicle does this to protect itself. The cheapest way to diagnose this one is to take it in. Remember, having it diagnosed does not mean you cannot fix it yourself. Just pay the fee and take it home if it is something you want to tackle.