CEL code: 0420 - Cat. Converter BAD ???

[philndz]

The vibe has 50,000 miles on it now and it has started throwing up a CEL. 0420 means its reading a "CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD (bank 1).Trouble areas are listed as:1) Gas leakage in exhaust system2) Heated Oxygen sensor3) Three-way catalytic converterThe system at AUTOZONE said it could be a defective cat. converter, an engine misfire, or engine oil leaking into the exhaust valve, guide seals, and/or piston rings.Anything you can throw my way is helpful....its gonna have to go to the dealer for sure.-Phil

[Raven]

I hope it is still under warranty, you must be close.

[joatmon]

Quote, originally posted by philndz »The vibe has 50,000 miles on it now and it has started throwing up a CEL. unfortunately, the US warranty is only for 36,000 miles

[philndz]

I have the 100,000 mile extended warranty w/ a $100 deductable

[joatmon]

Probably best to take it in, if it is a bad catalytic converter or heated oxygen sensor, would cost you more than the deductible to buy the part and put it in yourself, f you knew which to buy, and also assuming that it's not something else.Was that the only code set, or were there others? --------interpreted from the service manual, not knowledge that I had)There are two heated oxygen sensors, one on each side of the cat. The computer compares the two readings, and expects them to be different. If they are the same, or if one of them gives a constant output, then it can throw P0420. Apparently, if you run too lean, you can cause the sensor after the cat to put out a steady value, which the ECU can intrerpret as a failure. a lean condition could be caused by a dirty MAF, or bad MAF circuit. Running too rich can waste the cat.---------I suppose a bad or dirty MAF could be blamed on your short ram. would it be best to replace the short ram with the stock intake before taking it in.for warranty repair?

[Jahntassa]

Probably the sensor... When my cat went bad on my probe, you knew it. Not being able to rev above 2000 rpm really sucked..

[pmh013]

When my cat plugged, it didn't throw a CEL, so I can't tell you much about the code.However, I could tell the car just wasn't running right because my mileage would start to drop just a bit. Then, it would start to downshift to keep anything above 100 kph (62 mph). Keep in mind that this is an automatic. On a standard, you'll probably see the revs being limited.Keep us posted!

[champcaracing]

replace the cat, the sensor should be ok.