o2 voltage after cat change

Hey guy's it's my turn to throw a question in the pot!!!
Let me know what you think about this. I have a 1997 k1500.
I just changed the cats this weekend and just to see, I hooked up my Car Code laptop scan tool(which doesn't work worth a crap on 1996-1997 trucks)to see what my post cat o2 voltage was... I have about 40 miles on the change and the light hasn't come on yet but the voltage was .7/.6 +/- on bank 1 and .13 constant on bank 2. This was at idle. Before I changed them I had a p0420 which is bank 1. So why the change in bank 2 I remember looking at it some time before I got my cats and the voltage on bank 2 was all over the place but not that low...

Anyway feel free to ask me more questions and let me know what you think.

Thanks,
Richard

O2 sensor before the cats will be all over the place, as the ecm changes rich to lean. The O2 sensor after the cat should be unchanged, a constant low voltage, that is how the computer knows that the cat is doing its job.

Bank 2 is real lean or the 02 sensor is not working or the scanner is not reading it.
Try speeding up the rpm and getting the engine good and warm and rechecking.
Also here is a little info that may help.
http://www.troublecodes.net/articles/catfailure/
Also
DTC P0420, P0421, P0430 & P0431: Check Possible Cause Of Misfire DTC P0420 and P0421 indicates bank one catalyst system efficiency is minimum requirement. DTC P0430 and P0430 indicates bank 2 catalyst system efficiency is minimum requirement. Possible causes are as follows: Use of leaded fuel. Oil contamination. Cylinder misfire. Fuel pressure too high. HO2S sensor improperly connected. Damaged exhaust system component. Faulty ECT sensor. Faulty HO2S. Ensure ignition timing is correct. Retrieve all Continuous Memory DTCs. If misfire code(s) is not present, go to next step. If misfire code(s) is present, isolate cylinder and repair as necessary. Check HO2S Monitor DTCs If DTCs P0136, P0138, P0140, P0141, P0156, P0158, P0160, or P0161 were present in step 1), service as necessary before continuing. If none of these codes are present in step 1), go to next step. Check ECT Sensor DTCs If DTCs P0117, P0118, P0125 or P1117 were present in step 1), service as necessary before continuing. If none of these codes are present in step 1), go to next step. If any codes except P0420, P0421, P0430 and/or P0430 were present in step 1), service as necessary before continuing. If no codes except P0420 and/or P0430 were present in step 1), go to next step. Check Rear HO2S Wiring Harness Turn ignition off. Ensure HO2S wiring harness is correctly routed and connectors are tight. Repair or replace as necessary. If wiring harness and connectors are okay, go to next step. Check Fuel Pressure Turn ignition off. Release fuel pressure. Install fuel pressure gauge. Start engine and allow to idle. Note fuel pressure gauge reading. Increase engine speed to 2500 RPM and maintain for one minute. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. If fuel pressure is as specified, go to next step. If fuel pressure is not as specified, go to CIRCUIT TEST HC . Check For Exhaust System Leaks If exhaust system leaks, it may cause catalyst monitor efficiency test to fail. Inspect exhaust system for cracks, loose connections or punctures. Repair or replace as necessary. If exhaust system is okay, go to next step. Check For Exhaust System Restrictions Inspect exhaust system for collapsed areas, dents or excessive bending. Repair or replace as necessary. If exhaust system is okay, go to next step. Ć Check Manifold Vacuum Install tachometer. Connect vacuum gauge to intake manifold vacuum source. Start engine and raise engine speed to 2000 RPM. Manifold vacuum should rise to more than 16 in. Hg. If manifold vacuum is okay, go to next step. If manifold vacuum is low, go to step 11). Leave tachometer and vacuum gauge connected. Start engine and raise engine speed to 2000 RPM. On a non- restricted system, manifold vacuum should quickly rise to normal range as increased RPM is maintained. On a restricted system, manifold vacuum will slowly rise to normal range as increased RPM is maintained. If manifold vacuum is okay, no indication of exhaust leak or restriction has been detected and testing is complete. If manifold vacuum is low or slow to respond, go to next step. Leave tachometer and vacuum gauge connected. Remove exhaust pipe from exhaust manifold. Start engineand raise engine speed to 2000 RPM. If manifold vacuum is now okay, fault is downstream from exhaust manifold. Reconnect exhaust pipe to exhaust manifold and go to next step. If manifold vacuum is still low or slow to respond, fault is in exhaust manifold or intake manifold gasket. Repair or replace as necessary and repeat QUICK TEST. Leave tachometer and vacuum gauge connected. Disconnect muffler/tailpipe assembly from rear of catalytic converter. Start engine and raise engine speed to 2000 RPM. If manifold vacuum is now okay, fault is in muffler/tailpipe assembly. Repair or replace as necessary and test drive vehicle to verify elimination of symptom. If manifold vacuum is still not okay, fault is in catalytic converter. Repair or replace as necessary. Check tailpipe/muffler assembly for debris from catalytic converter. Test drive vehicle to verify elimination of symptom.

And
Make sure the fuel pressure is up to par.
This is for a hard to start code but will help a[on checking fuel pressure.
Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
Post back fuel pressure readings.

Good luck MT

Hey guys,

Thanks for the replies. I hooked up the laptop on the way home and watched the rear o2 values (for as long as it would stay connected). And it seemed like they were switching back and forth between bank 1 @ 2 rich and lean. But I got home and replayed it and the software has a column when the sensor is selected that shows you the average and the both stayed around .450 which is good right?? That is just and average though.
Changing the cats has made my truck accelerate smoother but I still have a little hesitation. It use to feel like it was bogging when it shifted to second. Now you have to really pay attention to feel any hesitation. I guess I was worried about having a stuck poppet or something and messing up my cat. If I have a problem hopefully my light will come on with a different code... I have 70 miles on it right now since the swap. I really need a scantool that will work with my truck... This carcode one seems like it would work really well but the problem I have with it seems to be isolated to 96-97 trucks only!!! and I wish I had the tools to clean the injectors and test them for leak down!!!!!

Thanks,
Richard