Calling on 986 Forum Master Mechanics

[jb92563]

Originally Posted by seventythree

Based on the above, I have two key questions:
1) Will a failing cat prevent the respective readiness monitor from resetting?
2) Is it true that I should be able to get the car smogged with 1 of 5 monitors in fail sate?

They keep changing the rules yearly. In 2015 they don't use the tailpipe sniffer on 2000 and newer cars and only rely on the computers diagnostic report so the CAT condition diagnostic would be mandatory so if THAT subsystem was not showing ready they can not pass your car.

[seventythree]

Thanks jb for your response.
Guys, I'm getting a little desperate here. I've been monitoring the O2 sensor voltages before and after the precat for both banks 1 & 2.
First off, while ideling, both banks look fine. Before cat is sinusoidal and after cat is fairly flat at around 0.8v.
While driving, the after cat voltages are fairly jumpy with bank 2 being a little worse. However, the before voltages aren't consistently up & down and seem to skip a beat quite often.
I am getting desperate because I don't want to spend 6 hours on my back changing out the precats just to find out the problem is still there. (I am a pretty accomplished DIY mechanic but having to wear reading glasses most of the time has taken a lot of the fun out of it.)

To recap the problem, the cat efficiency monitor is stuck in Fail state and won't switch to Pass even after ~300 miles of driving. The other 4 monitors are in Pass state and I haven't got another CEL since I turned off the last one and tried to smog the car 9 days ago. It's a 2002 Boxster base with 96 Kmiles.

Please respond if you can help me diagnose the problem with more accuracy.

Thanks again.

PS, If I let the car idle for a minute or two, the period on the sine wave becomes as tight (short) as we see in most illustrations. However, the period is much longer most other times.

[JFP in PA]

Originally Posted by seventythree

Thanks jb for your response.
Guys, I'm getting a little desperate here. I've been monitoring the O2 sensor voltages before and after the precat for both banks 1 & 2.
First off, while ideling, both banks look fine. Before cat is sinusoidal and after cat is fairly flat at around 0.8v.
While driving, the after cat voltages are fairly jumpy with bank 2 being a little worse. However, the before voltages aren't consistently up & down and seem to skip a beat quite often.
I am getting desperate because I don't want to spend 6 hours on my back changing out the precats just to find out the problem is still there. (I am a pretty accomplished DIY mechanic but having to wear reading glasses most of the time has taken a lot of the fun out of it.)

To recap the problem, the cat efficiency monitor is stuck in Fail state and won't switch to Pass even after ~300 miles of driving. The other 4 monitors are in Pass state and I haven't got another CEL since I turned off the last one and tried to smog the car 9 days ago. It's a 2002 Boxster base with 96 Kmiles.

Please respond if you can help me diagnose the problem with more accuracy.

Thanks again.

PS, If I let the car idle for a minute or two, the period on the sine wave becomes as tight (short) as we see in most illustrations. However, the period is much longer most other times.

If you are throwing P0420 and/or P0430, and you know there is nothing wrong with the O2 sensors, you have bad cats, which are not going the heal on their own. You are also not going to sneak this past the emissions inspection.

[seventythree]

Thanks JFP,
Can you guide me through the process of eliminating the O2 sensors as a culprit.
I just want to tackle the pre-cat replacement project with more confidence.
TIA