While on the hwy my SES light will come on after about 15 minutes of driving....once I get to my destination shut down when I leave and re-start SES light is gone......Where should I be looking???
no codes show when I use the paper clip jumper......

 

when you say "no codes" do you get a C12 at least?

Try this: C4 Guru - Reading CCM Codes.

 

yes C12 does display.... no Bad codes

 

Wow Bogus, nice write up thanks, that one will be saved!

 

I have a 1989 c4 - but the link on thread #2 mentions 1990+.

I am very familiar with my obd2 honda's paperclip trick to pull codes.

Is there a similar trick for a 1989 c4? I have the SES light on...

 

Code Recovery: 1984 through 1993:

To recover ECM codes from the 1984 through 1993 Corvette, place a short as shown below between pins "A" and "B" on the ALDL (Assembly Line Diagnostic Link) connector. This connector is located under the dash just to the right of the steering column and has space for 12 pins although not all of the cavities will be populated.

Turn the ignition switch to "On" but do not start the engine.

Depending on the model year, either the "Check Engine Light" or the "Service Engine Soon" will begin to flash.

As the code display sequence begins, you will see a flash followed by a pause and then two flashes. This is the indication for the number "12". The number 12 is a delimiter intended to show where the ECM code display starts and stops.

Code 12 will flash three times and then any stored codes will flash. When all codes have been displayed or if there are no stored codes, the number 12 will again flash three times.

For example, a problem with the EGR system (code 32) will be shown as 12, 12, 12, 32, 32, 32, 12, 12, 12.

This would be displayed on the Check Engine/Service Engine Soon light like this:

12: flash (pause), flash, flash, (long pause)
12: flash (pause), flash, flash, (long pause)
12: flash (pause), flash, flash, (long pause)
32: flash, flash, flash (pause) flash, flash (long pause)
32: flash, flash, flash (pause), flash, flash (long pause)
32: flash, flash, flash (pause), flash, flash (long pause)
12: flash (pause), flash, flash, (long pause)
12: flash (pause), flash, flash, (long pause)
12: flash (pause), flash, flash (long pause)

The ECM code display will repeat until you turn off the ignition switch and remove the short.

 

thank you. this is why i love the internet.