Nico

It is a 91. Runs fine. But, when doing the highway for approx 30 -60 minutes, the SES light comes on. No overheating, everything seems ok. When I stop the engine and start again, the SES is off. When continuing the highway, after 20 - 40 minutes the SES comes on again.
There are no codes stored.
How can I find the reason? heeeeelp

chileverde

Take your obd scanner with you and see if you can catch a code at that moment when the light comes on?

thats all i can think of....

vader86

Intermittent Code 32, EGR.

Look down the page http://forums.corvetteforum.com/c4-t...t-65-75-a.html

gbrtng

Or, light but no code = flakey ECM? The scanner will help pin this down.

floridamale

You can also use a paper clip to read the codes

1985-1991: ECM Codes
Code #12: Normal No Codes.
Code #13: Open Oxygen Sensor Circuit.
Code #14: Coolant Sensor Circuit Low.
Code #15: Coolant Sensor Circuit High.
Code #21: Throttle Position Sensor High.
Code #22: Throttle Position Sensor Low.
Code #23: Manifold Air Temperature Circuit High.
Code #24: Vehicle Speed Sensor.
Code #25: Manifold Air Temperature Circuit Low.
Code #32: EGR System Failure.
Code #33: Mass Air Flow Sensor High.
Code #34: Mass Air Flow Sensor Low.
Code #36: Mass Air Flow Sensor Burn-Off Function Fault.
Code #41: Cylinder Select Error.
Code #42: Electronic Spark Timing.
Code #43: Electronic Spark Control.
Code #44: Lean Exhaust indication.
Code #45: Rich Exhaust Indication.
Code #46: Vehicle Anti Theft Fault.
Code #51: Faulty Mem-Cal.
Code #52: Fuel Calpak Missing.
Code #52: (1990-91 Corvette Only): Engine Oil Temperature Sensor Low.
Code #53: System Over Voltage.
Code #54: Fuel Pump Circuit Low Voltage.
Code #55: Defective ECM.
Code #62: Engine Oil Temperature Sensor Circuit High.

Nico

Should like to do that, but don't have a scanner.
Will it be possible to connect a laptop?

Nico

Thanks a lot, reading the tread it really looks like the same problem. I will check the EGR sensor!!! Let you know the results.

Nico

Thanks for the info. When I can read codes with a laptop or so, this list will be helpfull. But the reply of VADER86 looks very similar to the problem I have. So that will be the first I will check. I do not have a scanner or laptop and there are no codes stored. So if it is not the EGR temp sensor, than I will try to organize a laptop to read codes at the moment it appears.
Regards.

Nico

Vader, I could not locate that sensor. In the thread there is a photo, but in my 91 there is no such sensor!! I can not find a wire that should connect to that sensor either. Is it possible that my engine does'nt have one?

vader86

1991 has EGR. If it doesnt have it, then someone removed it.

Nico

Vader
I have EGR, but there is no temp sensor. I did look, but I couldn't find a plugged hole either at the place where the sensor is mounted in the photo in the thread. There is als very little space to put it. And no loose wire that has been connected.
Can it be that there are versions with EGR but without sensor?
I made photo's but can't find a way to include them into this answer.

vader86

There is no EGR function without the sensor/solenoid. Either its there or someone removed it.

http://members.shaw.ca/corvette86/EGR%20System.pdf diagram C7-5

You can create a photobucket account and upload the pics there or some webservice.

vette079

It all depends were/how you look...
On a 1991, there is no sensor, the function is incorporated in the ECM.
There is a EGR solenoid otoh, it 's located right under the TB/plenum in the front.
The 86 doesn't have that one.
Where the 86 has a temp sensor on top of the isolated tube at the rear of the engine, the tube on the 91 continues right down to the cat/exhaust.

My 2 bux