Quote:
Originally Posted by Rooskey
Well I was cruising around and my service engine soon light came on. My mechanic has a KAL-Equipment obd-II scanner and the code came up as PO420 (catalyst effeciency below threshold). Any idea's on what it may be. I have FI longtubes with stock nismo exhaust.
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This is triggered because the 2nd O2 sensor is detecting is detecting too much oxygen in the stream relative to the upstream O2 sensor. With a catalytic converter this would mean that the catalyst in your converter was used up and you need a new cat to properly scrub the exhaust.
This is a common problem with test pipes, LTH. You can get an Uprev tune and turn the code off permanently or try and come up with a solution to reduce the amount of air getting to the sensor, e.g. extenders, steel wool etc. Or worst case I guess you could try two of these.
O2 Simulator Mini Cat Cel Fix
Exhaust leak where the header meets the exhaust could also cause this as some outside air will sneak in to the mix.