Q: 2004 Nissan Altima- Won't move when the code reads p0420 on the scanner. Did my transmission go? Is it my catalytic converter like code said?

asked by on December 01, 2016

2004 Nissan Altima 4 cylinder. Last night my check engine light came on. I drove to work this am and went to autozone and service code came back as P0420.. When leaving work my brake light and battery light came on in addition to check engine light while driving. Stopped at daughters daycare to pick her up and car would not start. I was able to get a jump and car started but when I press on gas it does not move. Did my transmission go? Is it my catalytic converter like code said? What steps should I take? Please help!!

My car has 143000 miles.
My car has an automatic transmission.

Hi there. The code P0420 means that the catalytic converter is below threshold and cannot burn off any emissions in the exhaust stream. The O2 sensors have pickup this fault and put the engine into limp mode. As for the vehicle not moving, the exhaust may be plugged up causing the engine to not breathe properly. Put the vehicle in drive and set the parking brake. Fully step on the gas pedal to the floor and have someone feel the exhaust pipe. If there is very little pressure coming out of the pipe, then the catalytic converter has plugged up and needs replaced. If the pressure is normal, then the computer may have locked the transmission out of the drive cycle. If you need further assistance with your vehicle not moving due to the code p0420, then seek out a professional, such as one from Your Mechanic, to help you.

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