P0430 troubleshooting

[openspaces]

Just had the P0430 code pulled on my 2006 with 82k miles.

Planning on doing the following
1) check gas cap and try a bottle of injector cleaner (can't hurt)
2) look at cats for obvious "issues"
3) assuming cats look good replace O2 sensor(s)

Only question is can I check O2 sensors to determine they're bad?

Already pulled the fuse to reset the code so i may do step one and if it stays off I'll consider myself done till next time.

Thoughts?

[disallow]

My Superchips Cortex will pull up the voltages and trim levels for the front and read O2 sensors. I'm not entirely sure how helpful this is, but I guess you can watch it to see if they are acting erratically or at high voltage. There have been a couple good posts here on how O2 sensors are supposed to operate.

[smj999smj]

99% of the time when you get P0420/P0430 code(s), it's the catalytic converter. You can check the sensors, but you need a scantool that can graph O2 sensor voltages. O2's should constantly cycle within the range of 0 volts to just over 1 volt. The ECM looks at the number of cycles from the front O2 sensor and compares them with the number of cycles of the rear O2 sensor. The catalyst sits between the two sensors. If the catalyst is doing its job, the ECM should see approx. half the amount of cycles at the rear O2 sensor compared to the front. If the number of rich/lean cycles are relatively close between the front and rear sensors, then the catalyst has become inefficient and will trigger a trouble code.

[Tech]

R51's have A/F sensors pre-cat that don't work like regular 02 sensors (varrying current, not voltage). with most generic scan tools, you won't see much usefull info.

The post cats are still zirconia 02's.
you can check those, but will only be able to work under the assumption that fuel control is good upstream

Besides a difference in frequency pre and post (with conventional 02's), you should see a decrease in amplitude. you should see basically a flat line with a slight rich bias.

you can also go oldschool and look for a pre/post can temp difference. 100* minimum is the old standard (once you warm up to reach light-off).

[openspaces]

Just a quick followup

Reset the light and made sure to click the gas cap 2-3 times and the light has stayed off for >300 miles. I'm not saying the "issue" is fixed but gives a little hope instead if replacing the parts first.

[rxman]

I need some advice. I have a 2005 Pathfinder with about 185,000 miles. I have the P0430 code, but I do not think it is my cat. My reasoning is based on my O2 sensor readings. If I am correct, sensor 1 is before the first cat and sensor 2 is after. With the car engine off or at idle, sensors 1 and 2 on bank 1 both read 0.3 V. On bank 2, sensor 2 also reads 0.3 V, but sensor 1 reads 0.6 V. Similarly, as I drive the vehicle, sensor 1 on bank 2 always reads much higher than all the other sensors (and it is the only sensor that exceeds a reading of 1V). The post cat sensors on both banks always have similar numbers. Am I correct to assume my pre-cat sensor is faulty?

[HoneyMonster256]

I'm so glad I found this post, I have 130,000 on my pathy and got this code over the weekend, It was telling me either an O2 sensor gone bad or Cat problem.

My question is who can read the O2 Sensors to get the voltages and I'm going for an exhaust flow reading to see if it's a CAT problem. I already have a Cat back system so I might just spend the money and get new CAT's while I'm at it.

Also remember we have upper & lower Cats on each side.