C4Me

Ok. I'm a newbie to Corvette's and have only had mine for a few months but need some help. The "Check Engine Soon" light coming on after approx 30 minutes of highway driving. I did not noticed any change in performance. When I reached my destination, it took about 45 minutes, the light was still on. My wife went shopping (that time of the year) I returned about an hour later and started the vette and the light was out. On our trip home, 20 to 30 minutes into the drive, the light came on again.

How do I identify what is causing the check engine light to come on?

One other thing to add. Last week I replaced the the whole exhaust system when my pre-cats went out. I put in a Front Y-pipe that takes out the pre-cats that goes to just one cat. Then put in a rear Y pipe with crossover tube to Borla mufflers.

Thanks

Don

dlmeyers

I'm willing to bet, (not much but suspect several would join me) should you pull your codes, it would be a 32.

Your EGR valve requires back pressure for normal operation. With a free flowing exhaust, the back pressure is no longer there providing the signal for proper EGR operation.

You can get a chip to solve this problem.

If you have a service manual, head for a code 32. The service manauls offer excellent schematics and trouble shooting diagrams.

Also, check the archives for "Code 32" or "EGR".

Several list members have web sites with trouble shooting tips. Should be found in some post for 32 or egr.

Just speculation.

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ittlfly

:iagree: without pulling the codes, I'd bet a steak dinner on code 32 since you have modified your exhaust. To answer your question, the check light is telling you that the ecm has set a fault code.

C4Me

Thanks guys. I had a feeling it would have something to do with the exhaust. I will check on the code. I should be getting a service manual soon.

Appreciate the quick ....
:cheers:

Don

PeteL

You should post the year of your car, some don't have sigs inabled.

You have an 89, with a negative backpressure EGR valve, which is not as sensitive to exhaust changes as the 90, 91 positive backpressure EGR valve on L98's. If you have an EGR code, I would suggest persueing it. I have no pre-cats, fairly high flow main cat and a 3" B&B catback with no EGR code on my 89.

To check codes:

Fashion a small paperclip into a U shape.
Locate ALDL connector just above your right knee when sitting in the drivers seat.
Use paper clip to connect terminals A and B together. A is the top row far right and B is the slot just to the left of A on the top row. There may be a cover on the connector.

Turn ignition ON, but do not start.

SES light will begin to blink. It will report code "12" three times: blink, blink-blink, pause. Then will report any codes stored, three times each. When all stored codes have been reported it will begin over at code 12. Turn key off, remove paper clip.

Post codes here and somebody can help.

To reset codes, remove negative battery terminal - OR - (to save radio presets) remove ecm connection (orange wire) near positive battery connection.

Good Luck

Pete

Petros89

Did you pull your codes yet?I get the same check engine light when i get on the highway.Mine is a code 13 (sluggish O2 sensor).I think the problem is that the O2 sensor is falling out of it's operating range.Less backpreassure from the Y-pipe and a low cruising rpm would cool it down.I am using the Y-pipe with no cat and the SES light comes on within a few minutes of highway cruising.Will try heated O2 sensor soon.Anyone else experience this problem?

C4Me

thanks Pete. I will remember to put the year in going forward. Yes it is an 89. I was looking through the forum to see how to check for codes. I appreciate the help and once I check them tomorrow I will repost.

Petros89--I'll let you know what code shows up.

I wish it was not so late here, I want to go check the codes now. It will bother me all night. My wife says I'm getting obsessed. Does this happen to the rest of you Corvette owners?

Don

PeteL

13 is open circuit to O2 sensor. You may have a bad connection or bad O2 sensor. I would work that troubleshooting first, doubt you need a heated O2.

dlmeyers

With regards to your wife's observation.

Obsessive compulsive behavior. Ahhh, welcome to the group. When it comes to cars, tools, and test equipment, consider myself as clinical.

Noted you're getting the service manual, really a big help. The front of each major section will often explain some operating priciples of a system. Fun reading. The book, coupled with a good multimeter, amazing how much trouble shooting is done with just those two items. Paper clip as code puller is fine however with my disorder, bought a used Snap On scanner, updated a cartridge, and use it on all four vehicles maintained. Just can't help myself. Love reading all those values noted by the Elecronic Control Module (ECM).

You may enjoy working on this car ALMOST as much as driving it. Dash work excluded.

Enjoy the car. Fine motoring pleasure.

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BillV

Had the same problem with my 88 C4 just a few months ago. The light would come on after a short drive and after setting for a while it would turn off. Sometimes it would go for days without turning on and them it would start again. It was realy bad on hot summer days. I diagnosed the problem as the Computer. I had the code pulled and it was for the relay that injects fuel into the cylinders on startup. Can't remember the code but the relay was 15.00. After installation of the new relay the service engine light still came on. I was then told it was a short leading from the computer to the relay. After a lot of rewiring and time I finaly decided to change the computer. ZIP Products on the forum Mall has them. You can't find new ones any longer and the dealer wants about $250 for what you can get from ZIP for under $100. It took care of the problem and the car is running fine. If you are going to replace parts, I would start with the computer. Not to dificult to change out , just pull the computer out from under the dash, unplug the two connectors and install the old prom, fit it back under the dash and your finished. Good luck.