Check engine light questions

[CL8]

One of the emergency maneuvers I have our drive students perform is having the car "stall" in the middle of a turn.
I take them to a quite road or large parking lot, have them start into a turn at normal speed (about 10mph right turn, 15mph left turn) as they start the turn, I turn the key to shut off the engine. they are to continue to turn until almost straight (to see how it feels to steer with no power steering) then push the gear in neutral, restart, pull it back in drive and lightly step on the gas.
Recently one of my students stepped on the gas, very hard, in neutral before he put it back in drive. We did the maneuver a second time and he did the same thing. The Check engine light came on immediately as he pushed the accelerator in neutral the second time.
I know doing that triggered the light, I told him not to worry about it, we ended the lesson about a half hour later, I figured the light would go off before the lesson ended, it didn't go off until 2 days later.

The vehicle is a Toyota Echo

My question is,
1.What exactly was happening in the engine when he did that, to set off the light?

In training I was told when the Check engine light comes on it means the computer senses too much pollutants coming from the exhaust system.
2. Is that correct, and is there a difference between the check engine light and the emissions warning light?
3. Why would the light have stayed on for two days after that?

Thanks for any input,
Cl8

[UncleBob]

Originally Posted by CL8

In training I was told when the Check engine light comes on it means the computer senses too much pollutants coming from the exhaust system.
2. Is that correct, and is there a difference between the check engine light and the emissions warning light?

anything emissions-related will set the light, although the umbrella of what is considered "emissions-related" is very broad.

3. Why would the light have stayed on for two days after that?

depends what code was set. Some codes are "hard codes" and will not turn off until reset. Other codes are retested and will shut off on their own. But your code seems to be a hard code.

Different manufacturers do it differently. I've seen similar situations set a MAF out of parameter code on GM's, but whatever it is, it isn't really important. Just get the code reset and you'll likely be fine.

[CL8]

Thanks UncleBob.
Since I haven't seen the light come on again I don't think I need to reset the code.
If anyone else can explain how pushing on the gas in neutral triggers the engine light that would be great!

cl8

[shorod]

You really need to get the code checked to determine what the likely reason was. Maybe the Echo has a code for "engine overrev occurred" or similar. Many of the chain auto parts stores will read the codes at no cost. Even though the light is currently not illuminated, there will still be a stored code. It might be a manufacturer-specific code that the parts store won't have a definition for, but in that case you could post the exact code number on the appropriate forum and expect an explanation.

-Rod

[serge_saati]

Originally Posted by CL8

If anyone else can explain how pushing on the gas in neutral triggers the engine light that would be great!

cl8

Maybe the engine has knocked.

[CL8]

Originally Posted by shorod

You really need to get the code checked to determine what the likely reason was. Maybe the Echo has a code for "engine overrev occurred" or similar. Many of the chain auto parts stores will read the codes at no cost. Even though the light is currently not illuminated, there will still be a stored code. It might be a manufacturer-specific code that the parts store won't have a definition for, but in that case you could post the exact code number on the appropriate forum and expect an explanation.

-Rod

Thanks, maybe I'll go to the Napa Auto Parts store near me and have them read it.