Need help, where does this 2 wire plug into?

[GoToGuy]

How do you know the cats are plugged, was an exhaust back pressure check done?
Do you have some kind of scanner to check O2 sensor operations ? Did the misfire on 3 come up after the tune up?
What's the P0157 code ?

 

[RanchWelder]

Good questions...
So many O2 sensor failures because the wiring got ruined off road or the cat cooked the harness.

Check your wiring please. Then post after every connection is found to be 100% functional.

The O2 sensor on the Suburban after the Y-Pip[e connection, tends to get ruined first, because it is pointed up in an area where dirt, grime and heat cause it to be difficult to remove.

The post cat O2 on the downstream sensor after the passenger side cat.

If it sucks to get out, we have a possible winner!

 

[LuckyJ427]

How do you know the cats are plugged, was an exhaust back pressure check done?
Do you have some kind of scanner to check O2 sensor operations ? Did the misfire on 3 come up after the tune up?
What's the P0157 code ?

 

[GoToGuy]

Scanner To check all four O2 sensors. Do a visual any wires broken, missing.
Check spark on #3 to start with.
Start with known problems, fix those, then the next.

 

[LuckyJ427]

Spark is good, but #3 is a dead hole for sure. Ill do wire inspection next. Thank you.

 

[GoToGuy]

Dead hole would refer to damaged and or no compression. Has spark including the spark plug is good. Then probably a fuel issue. Do you have the upgraded injection system?

 

[RanchWelder]

I have a set of good OEM injectors, (100K miles), but you cannot buy them because I'm not allowed to help you out unless I have 100 posts.
Good Luck.

 

[Russ B]

The picture does not show the power steering pump on that side of the engine, so not sure the EVO would be for that. If you can get electrical schematics for the K1500 that should show you what is in that area. Note the color of the wires to that connector and matchup with the schematic to see what it does. Probably some device you do not have. Also check the RPO codes in glove box.