Did the dealership disconnect your battery for about 30 minutes. Cause if they didnt, the computer would reset itself eliminating the codes. On the other hand, before i installed my exhaust, i had to loosen the H-Pipe at work. I drove on it loosened for about 100 miles and the service light came on. I figured it was the O2 sensor on the hpipe. I was right, replaced it, disconnnected the battery, and the light was gone.

 

if one goes bad you SHOULD replace allof them, but with thatsaid theres noway i'd do that. replace the 2 in front of teh cat and that will likely solve your problem. the two after the cats dont often fail

 

I agree, I just replaced my 2 in front ones, and it solved it. The rears are less prone to failure. My milage was going to hell, and the power started to suffer some. It's back to normal now.

 

hey tex, what they gouge you for on those ?

 

They are around 50 or so each.

That's at O'Riellys. Someone said you might could get them at Napa for 30ish. Worth a look to find out.

 

I just replaced my on my '94 k1500 blazer. It is right in front of the cat converter. Just screw it off and plug in the wire. Mine cost $70 at NAPA because it had to be a three prong plug in. It started at $20 at Autozone but it wasn't the right one. And if you havn't already change the throttle body sensor with the high miles it will help your throttle response and it will cost around $20.

 

the 3legged wired O2s costs $50 at least. and if you got a 94up truck, you got that sensor. its one of the heated ones, hence the extra wires. its not one of hose pigtailed O2s like that older trucks.

trailromper, do mean the throttle position sensor?

 

Is it possible for the O2 sensors to go bad without the service light ever coming on? My mileage has also started going to hell on my 2000 5.3 Z71, 72K. Did a tune up, installed K&N, and Gibson single side exhaust. That almost brought it back to normal, but not like before. It seems the O2 sensors are all that is left.

 

the possibility of your service light not coming on when it should is high, yes. like 50/50.

 

I never saw the light on mine. I was told last summer when I had my tranny scanned for a routine maintnance check. I didn't change it then, after a while it started to get the bad mileage and slight power loss. I drove it for a while with it bad and never had a check light come on.