92 olds 88 clear codes????????

I have a 3.8 L that has decreased fuel economy. I checked the codes and replaced the o2 sensor and reconnected my mat sensor. I got the car used so it's been interesting. Anyway I can't clear the codes. Tried disconnecting the batt. no good, went to a mechanic with snap-on code reader and he couldn't clear them. Any help is greatly appreciated.

Welcome to AF. What were the codes and how do you know they are fixed so the codes can be cleared, not much info here.

Sorry about the no info, I'm new to this. The codes were O2 and MAT sensors. Replaced them and tried to reset but no good. I also have a security light on. It does go off at times, but mostly stays on.

Seems like I am asking you more questions than you are asking us. There is no mat sensor number one, there are more than one o2 codes, some point to engine operation, some point to replacing the sensor or wiring repairs.. When you get all the right info, post back for some help.

Okay i'll try again. I have a 13, and 23 code. The mat sensor was unplugged, and I replaced the O2 sensor. I have lost about 115 miles to the tank. I also drive about 450 miles a week to work so it cost alot. Have you came up with any ideas on the security light that comes on at different times? Thanks.

23 is the intake air sensor in the ducting to the throttle body, is this what you call the mat that was disconnected. This should be scanned with a full function scanner and look at fuel trims o2 sensor activity and such. The security lite is not an immmediate issue, another complex problem. Look inside the fuel pressure regulator hose for raw fuel, also.