Chasing codes on my 97 Tahoe

[speedygonzales]

The previous codes 160 & 161 were after cat O2s. The 430 is cat efficiency.

The rear (aftercat) O2s are only used to check on the health of the cat. They do NOT have anything to do with control of the engine. That is what the front O2s are for.

You need to understand how and when the engine checks on the health of the cats. And thus reading the rear O2s. They are not used constantly.

One thing I can tell you is our vehicles do not like aftermarket sensors. I could never get Bosch to work. And it took days for the code to appear.

Keep that in mind.