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Cant' read codes from ECM

1998 Buick Regal LS 3.8L

The ‘Service Engine Soon’ light is constantly illuminated. I borrowed an OBD-II code scanner but it would not read the codes. I got an error from the scanner, suggesting that I check the connections. I tried it several more times, jiggling the connector and even reinserting it. Then I went to another store and borrowed their scanner with the same results. The car seems to run fine. Thee is no stumbling or hesitation at idle or under load. I removed the ECM fuse for 30 seconds and reinserted it. The SES light was still on when I started the car. I disconnected the positive battery terminal for 30 seconds and the SES light is still on after reconnecting the battery. Any suggestions?

Whatever the issue is, it’s constant and immediate, or it would go off for a bit after you disconnected the battery. This is a case where you should probably take it to a shop, at least to find out the cause. Normally, we’d send you to Autozone to have them read the codes for free, but it sounds like you essentially tried that (twice). I know some dodges have a trick you can do with the key to get the light to “blink” the code out, but I don’t know about GM.

If my memory servers me correctly (it seldom does) that is an indication of a bad computer.

Good luck

30 seconds is not enough to reset the computer. Try 30 minutes and see what happens. If the light is still on there is a major problem. If there are no codes maybe it’s the computer. I hope, for your sake, that’s not the case.

No codes means to me that the computer is out. I could be wrong but sometimes common sense applies to computers. Not often. Now watch what happens, you replace the computer and it will tell you that you need so much work that the car isn’t worth keeping. Service engine soon isn’t the most ominous light that can come on. I wish there was a defective computer light.

Check to see that the wiring to the OBD2 port is ok and that there is 12 volts getting to pin 16. It is the pin on the lower right hand side of the connector as you face it.

How long has the SES light been on? If it has been on for a while and the car continues to run the same, and you have no problems, on a car this old it may not be worth sinking money into anyway. Run it. Im just speaking from experience. Im the type of person that I always buy second hand beaters. You know, the 500 dollar wonders. Most of them have had the check engine lights on for years and still run beautifully. However, if you want to dig deeper into this, try keeping the battery disconnected for more than 30 seconds. Try 20 or 30 minutes. 30 seconds isnt long enough. Hope all goes well. Let us know how u make out

Look for a fuse marked DLC (or, similar). This would be 12 volt power which goes to the scanner connector (pin 16) under the dash.

I don’t know if there are any codes. All I get is an error when I hook up the scanner.

It’s been on constantly for about a week. I also replaced the gas cap today; it seemed a bit too easy to get on. I pulled the fuse and left it out for about 5 minutes. I guess that I could try removing the battery line for about a half hour.

Yep, dont know about the Buick, but on my 97 Explorer checking this fuse is as simple as seeing if the cigar lighter works.

Is this in addition to the 10 amp ECM fuse under the hood? I’ll see if there is a DLC fues in either the under-hood or under-dash fuse box.

I can empathize with dodge racer 16’s stance; but, our EPA (Environmental Protection Agency) has set pollution level standards to protect us, even from ourselves.
Is there a State which doesn’t have emissions testing yearly, or bi-yearly? It seems the dodge racer 16’s State (province?) is such a one.
There are a lot of things, besides gas caps, which can cause the trouble code for evaporative emissions trouble light (CEL) to come ON. Check the dlc socket for the scan tool and check for 12 volts on DLC terminal #16. We needs dah code to helps you.

Check this answer about a 1998 Camaro with a “dead dlc”:

is this the same of maintenance due light??? service engine soon seems to signify that you are due for a routine maintenance and no codes would show…

Where have I been? Enjoying the Holidays instead of fixing the Buick. If I had been in town, I could have done both.

Cougar, I checked the voltage across pin 16 and pin 4 (and 5) and got an open circuit. There seems to be a wiring problem. Could that cause the SES light to illuminate? There is one fuse according to the wiring diagrams in the Haynes manual. I’m not sure I trust the Haynes manual, but it’s all I have at this point. Any other suggestions?