The connector for the O2 sensor in on the right side of the truck, next to the transmission dip stick tube (auto), it's not easy to get at. Kind of a one handed deal from underneath.

My bet is the fuel pressure is low. When the fuel supply is insufficient the O2 will read low voltage (lean).

The best deal is to connect a scanner to read O2 voltage, but it can be done with a voltmeter. I doubt that O2 sensor is the problem. If you get a voltage reading then you can "bleed" some hydrocarbons into the intake to see if the voltage goes up. You can use some carb cleaner or propane at the throttle body. If the voltage goes up the O2 sensor is good.

 

What's your ECT reading at the ECM and at the sensor in the intake. The O2S is just telling the ECM that according to the ECT reading and the fuel trim cell your in is off. This is what drive me nuts about AutoZone, they read the code and sell you a part, which turns out not to fix the problem. There are many other things that effect sensors. So get out your DVOM and start probing.

 

ECT?

where is the test point and what values am I looking for under what conditions?

 

Coolant sensor, and you can find the Ohm/temp tables on the net.
Test at the sensor and at the ECM, I can look at a diagram in a bit to tell you which pin.

 

Good replies guys , Best info I have seen on here in a while.

 

I had the same code plus code 22 I changed the TPS throttle postioning sensor out and it quit so I would recommend that (if you can buy an acdelco one) and rebuild your tbi gasket kit runs less than $25 and its worth it do it and buy 3-4 cans of Carb cleaner if it has over 100,000 miles on it (lots of carbon built up)