ECU throwing code but CEL doesn't come on
 

My friend's '98 GXE is throwing up 0205 (Idle Speed Control), however the CEL doesn't come on while driving:

Prior to buying the car two weeks ago, we went to check it out and noticed the CEL was on, so I extracted the code (0205) and told the guy who was selling about the problem (he's a mechanic as well, so said he would fix it before making things final). When we came back to take the car the CEL was no longer on, so we assumed it was all good. My friend expressed some concern over performance so we checked the ECU (despite the CEL being off) and still got 0205. I would think it would give back 0505 if the CEL wasn't on, so what does all this mean?

Re: ECU throwing code but CEL doesn't come on
 

Not all codes trigger the CEL. I am not sure about 0205, but I know 0304 is one of those. It seems kind of bone headed that some do and some don't. 0205 is a problem, there seems to be some problem with idle speed control

Re: Re: ECU throwing code but CEL doesn't come on
 

But the thing is that prior to buying the car, the CEL was on and was only throwing that code (0205). The mechanic/seller supposedly fixed it because the CEL was off when my friend purchased the car:

CEL is on, ECU throwing 0205
Mechanic/seller supposedly fixes problem
CEL is off, ECU still throwing 0205

Basically, did he fix it or just mess with the CEL/ECU to somehow keep the ECU and CEL bulb intact but disable it from lighting up (while driving)?

Re: Re: Re: ECU throwing code but CEL doesn't come on
 

take it to a different mechanic (or dealership). Pay, then return the bill to the original one and ask for your money or a gun to their head. :)

Thanks for all your input so far, guys.

Yesterday I checked the ECU again and got the code, then drove his car to see how it felt, while driving I noticed the CEL was flashing on and off in NO PARTICULAR PATTERN what-so-ever. I showed this to my friend and he said he'd never seen it do that. I then reset the ECU and it drove much better, I'm guessing the car sets up some kind of acceleration limiter when it detects the code?

Anyway, I haven't spoken to my friend about it since then, so I don't know if it came back on or not...

yeh i got the same thing but i didnt reset the ecu correctly