01 QX4 check engine light on P0430 Need Help

[kadoqx4]

So i had this this 01 QX4 for 6 months and had a problem with the power loss and the transmission would not shift at 3-4 RPM but never had got a Check engine light with that. so i figure out and asked a few people and this guy told me to change the MAF (Mass Air Flow Sensor) so i Put in a used but new MAF and that fixed the problem for 2 days and now. my last tread
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So After I put this MAF in IT drives perfect and runs like new and then after 2 days i get this Service Engine Soon light so i scan it and the code is P0430 witch is Catalyst Efficiency Below Threshold, So what is this what should i do? i change the O2 sensor like 4-5 months ago, but never had a problem till i fixed the MAF and the truck runs perfect and now this, i rest it and it comes back on after about 2 hour of driving? could it be cloged because it wasnt driving good before? any help would be great thanks

[asnorton44]

Based on the P0430 it may be the catalytic converters.

[ARKQX33V6]

Do a test with that new MAF and compare to the one removed. Also any change in the MAF housing since the MAF is determined by the heating/cooling effect of air surrounding that sensor and the algorithm may be upsetting the overall readings for the cat. The cat may not be the problem but the incident happened close to a change of sensors. It may be the new sensor, a disturbance in the enclosure of the sensor or a leak near or around that sensor or even the conduits going to the intake manifold at the TPS or anywher a vacuum line was left off.

Check it out carefully with a bright light

[CanuckQx4]

Id disconnect the battery and let it clear overnight, that problem so close to a sensor change would make me think it may not have anything to do with the cats

[kadoqx4]

But i cleared the code with the scanner and it co,es back after 2-3 days later? is it different if u disconnect the battery over night then erase it with the scanncer? its wierd i never had this problem till i changed the MAF and then it started coming? wierd

[CanuckQx4]

Yes clearing the codes with a scanner is different than resetting the ecu.

I cant guarantee it will fix the problem, but its a free attempt, and a good place to start

[asnorton44]

I'd check out the cats, see if any holes or anything. Also make sure your connections on the MAF are secure.

[alexf20c]

the only link between a MAF change and a Cat Below Threshold code is that the engine is now running properly with a proper air/fuel ratio, thanks to a properly working MAF sensor.

Nissan computers are notoriously sensitive in downstream O2S readings. all the code means is that the catalytic converter isn't working so well. it's not hurting your engine; only the environment.

you can keep resetting the code (either by disconnecting the battery or using a scanner to clear it; they do the same exact thing), or you can just wait it out. it is an intermittent issue and can go away over time.

when they say it's a Jeep thing, they're talking about breaking a U-joint on the trail. when they say it's a Nissan thing, they're talking about a CEL on the way to work. (specifically, a CEL for a bad cat.)

[kadoqx4]

ITs been a few months and still getting the codes P0430 and P0140, not understanding it didnt go away, i reset it like 20 times, what could it be there is like 4 O2 sensors? i Changed the one front right side about 6 months ago, anyone know witch other O2 sensor is the P0430? thanks