02 sensor

[1997]

read the fine print in the 95 manual, IIRC, a condition for a heated 02 is, 5.7 with a 4L60e trans, there maybe more ...

my 95 has a heated (3 wire) 02 sensor.

 

[Schurkey]

Assuming the O2 sensor is wired correctly and not defective, a 3-wire in place of a 1-wire sensor wouldn't cause problems. Possible it might solve some problems at idle.

 

[L31MaxExpress]

In my nearly 30 years of wrenching I've never seen a factory OBD1 GMT400 with a 3 wire O2 sensor. I'll take your word that they're out there, perhaps in Commiefornia, but I've never seen one.
And I have a Cali emissions equipped '95...

I have worked on plenty of them that had factory 3 wire 02 sensors. From memory all of them with computerized automatics aka 4L60E or 4L80E have them. I have seen them on the GMT400s as well as the TBI G-vans with the 4.3, 305, 350 and 454s. General rule of thumb is if it has an electronically controlled transmission with the Red/Blue connector TBI PCM with the part number ending in 6395 or 7427, it came with a heated 02 sensor. It is often referenced as a H.E.G.O or HEGO Sensor which stands for Heated Exhaust Gas Oxygen Sensor.

 

[tayto]

I have definitely seen them on the 4.3L e-trans trucks