I'm getting ready to change out my FPR and nut kit soon, and I'm also changing out the O2 sensor since it has never been done - truck has 103,600. So today I got under there and found I have the AFS74 (3-wire version) sensor, I disconected it from the connector and left it, turned on the car and drove around the block to see if It would throw a code, but no chack engine light came on... I know the light works cus' Its come on in other instances. Does this mean my sensor is not picking up? It is connected back now and I still plan on replacing the part, but I'm just curious as to why it wouldn't throw a code when disconnected. Any Ideas?

 

Does your check engine light come on when you first turn the key to the on position?

 

Yes sir.

 

If the ECM didn't reach closed loop operation, it may not set a code. You could try driving further with it disconnected if you want to see if it pops the light on.

 

Alright sounds like a plan. I will try that and keep ya's posted on the outcome.

 

Ok folks so this weekend I replaced my fuel pressure regulator and nut kit! I can't believe how much better the truck runs. WoW. Then I got my O2 sensor in the mail, drove around a bit more with the old one unpluged and it finally did set the check engine light off after about 15 minutes. At least I know it was working in the first place. Now to get the old one out of the exhaust... anyone have any ideas on how to unbolt the old one out? It is rusted soooo bad in place.

 

I sprayed mine with pb blaster, drove the truck around the block got the exhaust hot then loosened the o2 sensor. I waited until it cooled off the take it all the way out.

 

Thanks, I bought some PB Blaster (Whew! that stuff is potent) and sprayed it down, waited about 20 mins, and tried to get it off but I ended up rounding the bolt off. So I took it to my mechanic and he had to ultimately torch it off and we got the new one in no problem! OH! and torque specs for 1st gens AC Delco AFS74 Sensor is 35 ft-lbs.