Service Engine light on but no codes are present

[jtsuttle]

I have a friend with a 97 Blazer. The check engine light came on a couple of weeks ago. We tried to read the code with two different scan tools (snap-on and carchip). Neither scan tool showed a code present. Reset the light and all was well for about another week then the light came back on. Same deal this time, no codes are showing up. The vehicle is running fine and has gave no problems at all. Only problem is you can't get an inspection sticker around here with the SES light on. Any ideas?

[scholzee]

How familar are you we usimg the scan tools ? Have you used them successfully on a different vehicle ? There must be a code to turn on the light. Can you check the I/M readiness monitors with your tool, chances are after you reset the light one of the I/M monitors fails its test and then the light comes on. The EVAP is a typical one and does not run its test unless certian conditions are met, you can search foir the GM drive cycle which should get the system to run all its tests. Is the fuel gauge working properly the EVAP test needs an acurate fule gauge reading to function properly. If there is an Autozone near you have them see if they can get a code out, they will hook up for free and tell you what codes they get.

[MT-2500]

The snapon scanner has a section that you can check for history codes.
See what is stored in there.
If a code is not present at the time of scanner check the code moves to the history code section.
MT

[drdd]

Originally Posted by jtsuttle

I have a friend with a 97 Blazer. The check engine light came on a couple of weeks ago. We tried to read the code with two different scan tools (snap-on and carchip). Neither scan tool showed a code present. Reset the light and all was well for about another week then the light came back on. Same deal this time, no codes are showing up. The vehicle is running fine and has gave no problems at all. Only problem is you can't get an inspection sticker around here with the SES light on. Any ideas?

make sure it's an OBDII scanner. yeah, check history codes too ...

[jtsuttle]

I am very familar with both scan tools and have used the tools on many different vehicles. The snap-on does have history codes but that is showing no codes either. I will check on the fuel gauge and I/M readiness when I am with the vehicle again. Thanks guys...

[Markgc]

In the meantime can't you clear the light and take the vehicle straight in for the inspection especially as the light doesn't seem to come back on again for about a week.

Mark

[scholzee]

Originally Posted by Markgc

In the meantime can't you clear the light and take the vehicle straight in for the inspection especially as the light doesn't seem to come back on again for about a week.

Mark

Once the light is cleared the I/M readiness monitors are also reset. Most states now will fail a vehicle for emissions in the I/M rediness monitors are not all set to pass. thats why his light comes on later, one of the test finally runs and probably sets the light. If you want all the I/M monitors to try there tests you need to complete the GM drive cycle.

[Markgc]

My goodness what a nightmare. I think that I will keep my 70's and 80's cars going a bit longer.