1989 Chevy K2500 5.7l oxygen sensor

[CopaceticAF]

Running into code 13 on my 89 k2500 which clearly the o2 sensor isn't connected. I'm trying to track down where it plugs into I've looked everywhere and can't seem to find it. I have connector that is already connected which looks like it should be where the o2 sensor connects but if I unplug what's already plugged in and plug in the o2 sensor the truck doesn't start so I'm sure it's not the right connector. I got this truck as a project and am unfamiliar with a lot of the wirings. I know the 89 has the single wire o2 but for some reason there's also a dangling 3 prong connector near by that is unplugged as well with no clue what it's for. I attached some pics of what all I'm referring to. Any help is appreciated.

 

[CopaceticAF]

Running into code 13 on my 89 k2500 which clearly the o2 sensor isn't connected. I'm trying to track down where it plugs into I've looked everywhere and can't seem to find it. I have connector that is already connected which looks like it should be where the o2 sensor connects but if I unplug what's already plugged in and plug in the o2 sensor the truck doesn't start so I'm sure it's not the right connector. I got this truck as a project and am unfamiliar with a lot of the wirings. I know the 89 has the single wire o2 but for some reason there's also a dangling 3 prong connector near by that is unplugged as well with no clue what it's for. I attached some pics of what all I'm referring to. Any help is appreciated.

I should add in when truck was purchased it had headers that weren't carb legal so I swapped them out for the original manifolds.

 

[Schurkey]

Download the service manual set for your vehicle from the links in the "sticky threads" section of this forum.

Find where the vehicle-side of the O2 harness plugs into the firewall. Trace your vehicle's harness from there.

 

[Nad_Yvalhosert]

Looks like someone tried upgrading to a 3-wire heated O2 sensor. Remove the 3-wire and direct connect the 1-wire as OE designed it.

You say it doesn't start when connected? Perhaps the current O2 sensor is defective? The white part looks bent in the 1st pic...
Grab a scan tool and check the readings

 

[CopaceticAF]

Looks like someone tried upgrading to a 3-wire heated O2 sensor. Remove the 3-wire and direct connect the 1-wire as OE designed it.

You say it doesn't start when connected? Perhaps the current O2 sensor is defective? The white part looks bent in the 1st pic...
Grab a scan tool and check the readings

Thanks a lot for noticing that bend. Replaced the sensor and plugged it in and it finally fired up. I was told that wouldn't cause a no start but I guess it does. Greatly appreciate you