'97 GA - can't read engine codes

Car: '97 Pontiac Grand Am with 2.4L twin cam and a 5spd. 162k+ miles on the car.

I went to to start the car the other night and it was idling very rough as soon as I started it. Almost like it was mis-firing or something like that. If I tried to give it gas, it didn't get any better. A few seconds later, the check engine light comes on. Well I didn't have time to mess with it that night, so I shut it off and left it alone. I started it up today after work and it was idling fine, but the light was still on. I 'm not sure why it is running better all of sudden? Anyway, I wanted to find out what codes it had set off, from the other night when it was idling bad, so I took off to some local places to get it scanned. (The car ran fine by the way).

Well 3 different places and 3 different scanners and no one's scanner will read anything? I guess it's supposed to power on the scanner automatically when they plug it in under my dash with the key in the run postion, but no one's would do that. Two of them also tried powering it on manually and typing in the info, but that still didn't work. It kept telling them to plug it in?

I honestly think I have 2 different issues that just surfaced at the same time. I'm more woried about figuring out why I can't read my engine codes. Then I can figure out why it was idling rough and see if I have a different problem surfacing. I do supsect that the rough idling is steming off a problem I have been having where I shift into a higher gear at a low RPM and the car acts like it misses for a brief second or two, but this has never set off an engine light until the rough idling.

So tell me what I can check for this plug? Is the plug that they hook the scanner into known to go bad? Is my computer going bad? I did a quick check on fuses right there under the dash and didn't see any that were blown. My battery is brand new.

P.S. Also, just for some other info. Back in Sept when I had to get my emissions tested here in Georgia, they do an OBII scan and just hook up to this same plug to do that. Well the 1st place couldn't read it then, but they said they were having problems like that with other cars. So I went to another place, and theirs worked fine?

okay, I got an update. I was able to get someone to pull a wiring digram for my data link port on my car. It turns out that one of my 5 wires supplys 12v via the horn fuse (15A). Why through the horn fuse, I don't know, but I guess that was available.

Anyway, that reminded me that I had pulled my horn fuse a few months ago because during really cold weather, the horn contacts in the steering wheel touch and causes my horn to blow continuosly. (My neighbors didn't like that one night it happened). Anyway, I'm going to stick the fuse back in there and go and try to have the scan codes pulled again. That's kind of a sigh of reflief as to why I couldn't get my engine codes.

Hopefully that will be it and then I can move onto the code that it throws out and my other stumbling issue while I'm driving.

i had a similar problem with my car, The SES light came on and the mechanic couldnt pull any codes, and the car drove rough like it was misfiring i acutally couldn't get over 40mph. My timing was off on the car and the car had to be re-timed, Plus when he "cleared" the computer, the normal codes that say everything is Ok wouldn't come back, he told me then that the computer may need to be replaced.... Nothing ever came of it. My mechanic never saw anything like that happen before... So these are somethings to consider.

Okay, I went home last night and put that 15A fuse back in for my horn. I cranked up the car and with in about 20 seconds, the check engine light went out. I guses it was able to do a self diagnostic and figure out that there was no current issue.

I drove the car the 30+ miles to my father-in-laws shop just so I could play around with his scanner tool. I pulled the history of the codes and it showed up a misfire on cylinder #4. I decided to change the plugs and after getting them out, they definitely needed replacement.

Anyway, so the Check engine light is off and the car is running good with the new plugs, but I still have the low RPM stumble when I shift to the next gear. My father-in-law has suggested that I replace that plastic piece and rubber boots that sit on top of the plugs? He said he has seen those crack and cause problems?

Anyone got anyfeed back on those parts. After having that part of the car apart and seeing those pieces myself, that's a pretty crappy design if you ask me.

Yep that plastic/rubber boots that sits on top of the spark plugs tends to get brittle and crack over time. I've replaced all those things in our vehicle.