The old P0420

[fuzzy]

Hey gang,

Got my cat re-tuned for 91 instead of 94 and now I get the P0420 code come up after some highway driving.
I had the ECU map looked at and a modified version was put in place to remedy this (it was hoped), but it still appears.

The car has a little over 170k km on it, only one cat left (no up-pipe or downpipe cats), some questions:

1. could it be that the cat is going?
2. if I hookup my DeltaDash, what O2 readings should I be looking for (I'll check the service manual when I get home as well)
3. could it be that the O2 sensors are going?

Thanks,
Goni.

[AndrewR]

Goni,

This code usually means that the rear O2 is going bad.

Does not affect driveability or E-Test. I drive for a year with a bad rear O2, and passed driver clean.

As long as your cat is good, you are ok for that too.

[AndrewR]

Also, did they remove the rear O2 when tuning? Hmm...

[fuzzy]

Now that you mention it, I'm not sure if they removed the O2 sensor before tuning... Have to look into that.

I would be surprised if the cat was going so soon, I'll hook it up & log some info and see what the O2 is doing.

Thanks Andrew.

[Cavemanrjc]

scope both o2 sensors the front should switch between over .9 and under .1 v and should see a fast rise and fall rate on the sweep.
the secondary should read flat between .4-.6v
with no peaks and valleys in the pattern, just a flat line.
for a good cat.

or just have the monitor deleted :)

[STeveD]

By mentioning Delta Dash, I'm guessing you're ECUTEK tuned? Fourstar simply disabled my rear O2 with the last iteration of te car.