oldracer

Well this morning I installed a new after cat O2 sensor, an NTK model from Rockauto.com and ran the engine some after clearing the P0420 code that came back two days ago. As noted in my posts earlier, the second O2 sensor would have a slightly fluxuating voltage and dip about every 10 seconds or so. I feel this what might be triggering the 0420 code? This time the after O2 sensor voltage was rock steady at 0.75 with no changes or dips so maybe the cat is okay and the sensor should have been replaced 60K miles ago? It was the original one and the protective cage looked really bad from old age! I'll update this after some additional run time.

donbrew

You may have to wait for 20 cold starts. Several OBD tests need to run, and they can take their time. You cam monitor the I/M readiness (for emissions testing) with most readers, if gets to ready for testing with no code you may be lucky.

oldracer

My AutoEnginuity software and connection will run all the on board tests and it takes about an hour total but I figured I'd let the car's computer see how happy it is now with a new sensor. The old one looked like the ones in my race car after running super-low lead av-gas in a few races. They were Bosch but used only for the A/F meter.