Check engine light, "Engine power reduced" and "Engine disabled"
 

Last night, I left my key in the ignition (accidentally) for a few hours. When I returned to the car, the doors (thankfully) were unlocked, the battery was dead and the key was stuck in the ignition.

I used my android phone to poke around on this forum and on Google, and figured out how to get the key to release (http://www.answerbag.com/q_view/416947, if you're interested). Then I called my insurance company's roadside assistance for a jump. The car started right up, but the check engine light was on.

Today, I drove the car two separate times. The first time, the check engine light was on, but otherwise, the car seemed fine. After stopping at a store on the second trip, the car refused to restart. The display read "engine power reduced" and "engine disabled". I poked around, again, on this forum and read about someone who had the same problem but was able to restart the car after it sat overnight. I tried to restart the car again, and it restarted.

The check engine light is still on, however, and I'm afraid to use the car for fear of getting stuck somewhere. My car is a 2006 and is not under warranty. Any ideas?

If it shut the engine down, there's a better than average chance the ECM thinks that there's an issue with the TAC system, ie the throttle body.

Thanks for your reply.

What is the throttle body? What does it do and how much does it cost to fix?

It looks like for some people, this problem has spontaneously resolved or has appeared to be resolved by replacing the battery:

https://www.chevyhhr.net/forums/problems-service-repairs-42/engine-disabled-eng-pwr-reduced-5298/

I would unhook the battery for about ten min. then hook it back up. the pcm maybe little confused from the low voltage when the battery went dead.

If you look at my post, I said there's a chance "ECM thinks that there's an issue with the TAC system, ie the throttle body". I didn't say change the throttle body. :)

As far as what it is, it's an electric motor attached to a valve that lets air into the engine. At idle, or when you "step on the gas", the throttle moves to let more or less air in, allowing the engine to accelerate or decelerate. As you can imagine it's a critical part of the engine control system, and can cause some serious issues if things go wrong, (think Toyota) in order to avoid that, there are redundant sensors on the valve and Accelerator pedal, should the ECM detect anything wrong with those circuits, it can take various actions. They range from turning on the MIL, reducing engine power, to forcing engine shut down, depending on the severity of the failure.

Charging the battery isn't a bad idea, as driving it a couple of times is not enough to bring it up to a full state of charge. Before I disconnected it though
I'd check to see which codes were stored, and the conditions under which they where stored, and note them. That way should something be actually wrong, you'll have some information to give to the technican who will be working on it.

Erasing codes, erases more than that. It also erases Freeze Frame and Failure Record data that was stored with the code. To a technician who knows what they are doing, that information can be very valuable and aid in diagnosing a problem.

Disconnecting a battery can erase most codes and information, but it also erases stored values that the ECM, as well as other modules have learned over the period of time since the last disconnect. It can cause issues ranging from running rough, shifting hard/slipping, to actual part breakage as the various modules try to relearn what "normal" is for the vehicle now, not when it was new. A battery disconnect is not high on my list of things to do to a newer vehicle.

Honestly, if you don't know what a throttle body is, short of pulling battery power, I would suggest you take your car to the dealer/tech. No offense.

Since the problem started with a dead battery, that is where I would start. Jumping it will get it started but the battery has to charge up again. An hour at highway speed with few accessories in use would charge it. In town driving or idling won't bring it to full charge. A small battery charger will charge it in several hours. It is best to have an automatic one that won't overcharge the battery and boil the acid out.

If you have the original battery in your 2006, it is probably time to replace it. Original equipment batteries might last 4 years or more. The replacement batteries seldom last 4 years. Automotive batteries aren't designed to be drawn completely dead and don't live long when they do. The starter might crank the engine but if the battery voltage drops below 10 volts while cranking, the computer won't supply the fuel and ignition signal necessary to start the engine.

They make a device that plugs into your lighter socket and uses a 9 volt battery to supply power to the computer to allow it to save anything stored in it's memory while you change the battery.

In your case, I wouldn't worry about the memory because it lost everything when the battery went dead. The codes you are getting are more likely due to low voltage when trying to start it than other problems.