- Rebuilt catalytic converters banks 1 and 2 (front left/front right),
- Replaced central rear O2 sensor
- Replaced right rear O2 sensor
I’m trying to get my car to pass inspection but I have a P0420 problem. It’s usually just a “pending” code for a long time, but it seems that when the code is pending, the “CAT” monitor test stays on until the pending P0420 turns into a CEL. I’ve run it back and forth on the freeway a few times this weekend and usually can’t make it more than 5-6 miles of freeway without the P0420 waiting. If I keep it on slower suburban roads, I can keep the P0420 from showing up, but then I can’t do the CAT monitor test, so I’m no better.
I have searched this site and have already read a lot about P0420, including many (but not all) from this thread: P0420 Diagnosis
Car seems to run fine otherwise once started. I’ve never run it through misfires except for maybe 15-30 seconds a few months ago when the coil pack went, just to get it to safety. It makes no sense to me that the catalytic converter would be bad considering when it was replaced and the history. Over the last couple of weeks, I’ve had random problems trying to get it to warm up (would have to jump 3-4 times sometimes before it would catch). I also have a P0442 (minor evaporative leak) code that pops up, usually when the tank is about 1/2 full or less (mechanic said I have a small top/bottom liner leak).
Since I started noticing the problem a few weeks and have been trying to clear the codes I have been sure to use Top Tier gas and my last fill was 93 octane from Mobil (probably a waste of money but thought I’d give it a try). I probably ran two tanks of high-end gas, although before that I usually got gas wherever it was convenient.
Back to P0420, I have an OBDII reader that has a digital readout of all the sensors, but no graphic. I got some readings from the ECT and O2 sensors. I did the best I could trying to add up the numbers just by looking at the readout screen. They updated once a second so I can’t say it’s a perfect setup because the oscillations are faster than that so I’m collecting incomplete data as far as min/max goes. Here are the readings (I put them in the order the OBDII scanner read them):
in idle
- ECT – 195 and slowly increases to 200
- O2S B1S2 – ~ 0.550 to 0.700
- O2S B1S3 – ~ 0.530 – 0.550
- O2S B2S2 – ~ 0.150 to 0.800
- O2S B1S1 – ~ 2.76 – 2.80
- O2S B2S1 – ~ 2.76 – 2.80
At a steady ~60 mph
- ECT – 185, completely stable
- O2S B1S2 – ~0.700 to 0.800 swing… sometimes drops below 0.500V but very rarely
- O2S B1S3 – ~ 0.750 – 0.800
- O2S B2S2 – ~ 0.100 to 0.850 swing
- O2S B1S1 – ~ 2.76 – 2.80 (except when the foot is off the gas, still in gear, then it is approximately 5.4 V)
- O2S B2S1 – ~ 2.76 – 2.80 (except when the foot is off the gas, still in gear, then it is approximately 5.4 V)
Coolant temp seems fine to me. I’m assuming the O2S BxS2 sensors are the ones that should oscillate and the B1S3 should be steady. So what I think I’m seeing is that OS2 B1S2 is bad because it’s not swinging between lean and rich like it should and like B2S2 is.
Does this sound right to anyone else?
