Originally Posted by jhudgins
Sorry, I went and edited my post so you didn't see them.
If you have an overdrive switch, you didn't actuate it during the test. If no active o2 code, it means the ECU has locked out that sensor's input.
Although there are other possibilities that could cause 172 C/M, you have no active codes that would support most of them. 172 is also usually how 02's bow out.
You could clear the KAM (Kept adaptive memory) by disconnecting you battery for 5 mins. minimum. That should bump the 172 out of C/M & register an active KOER code in it's place, if the 02's still has issues. But it should be replaced regardless, as it is far beyond it's effective service life anyway.