P0340 is a cam position sensor code, which is not an uncommon failure on VQ-series engines and can cause P0420/430 codes to occur. I would replace the cam position sensor; there may be a couple, so make sure you get the correct one for this code.
If you get through the treated gas and replace the cam sensor, and the codes for the catalytic converters still trigger, then it is likely that you have can efficiency problem with the front converters on the given bank(s) that the code(s) imply. Efficiency problems won't cause any problems, it's only when the converters are clogged, restricted or deteriorating that they are an issue. You could try the O2 sensor spacers; make sure you only put them on the downstream sensors and not the upstreams! They work by pulling the rear sensor element partially, but not completely, out of the exhaust stream, thereby giving them an inaccurate reading and tricking the ECM to not trigger the codes. It often works, but not always, and is technically not legal, as it is considered "tampering" with the emissions system. In a place that checks for emissions and tampering during state inspection, it will cause them to fail the vehicle for "emissions tampering." In states that don't inspect, they will likely ignore it. You can get pre-made O2 sensor spacers in addition to making them yourself out of anti-foulers.
2002 4x4 SE
Moderator: volvite
smj,
From what I can tell those cam sensors run anywhere from 30-70 a piece. And, since the rig has not thrown any codes for a bad cam sensor, I'm hesitant about shooting from the hip and throwing parts at. However, thank you for the insight about those sensors and how they might lead to a false code towards a catalytic converter. I drove the truck again today and the SEL tripped another 3 times. Each time it tripped it popped the same code: P0430. And, the light tripped exactly around the 30 mile marked each time. So, my previous theory that it was getting better is now scrapped. I think I am gonna go ahead and install this spark plug non fowler tomorrow and see if the light goes out. Again, thank you very much for technical advice.
From what I can tell those cam sensors run anywhere from 30-70 a piece. And, since the rig has not thrown any codes for a bad cam sensor, I'm hesitant about shooting from the hip and throwing parts at. However, thank you for the insight about those sensors and how they might lead to a false code towards a catalytic converter. I drove the truck again today and the SEL tripped another 3 times. Each time it tripped it popped the same code: P0430. And, the light tripped exactly around the 30 mile marked each time. So, my previous theory that it was getting better is now scrapped. I think I am gonna go ahead and install this spark plug non fowler tomorrow and see if the light goes out. Again, thank you very much for technical advice.
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