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

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.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1,000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. 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?

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Trip Counter, Clock & Radio Presets Are Resetting.

Your concern sounds to me as if there is an electrical problem in the vehicle. Many electrical problems can be traced back to poor connections or corrosion. We will start at the battery as this is the heart of the...

Q: Q: Car stalled and now won't crank

No start conditions are complicated to diagnose sometimes because of all the variables. This is especially the case in this situation where we have very limited information about what the vehicle is doing besides not starting. Questions such as: is...

Q: I have a 2007 Nissan Altima that won't crank. Some guy attempted to put a radio in and everything went South from there my radio w

Hi there. I'm sorry to hear this happened to you. Unfortunately, it's too common for inexperienced people to make mistakes like you've listed. The best way to resolve this issue is to have one of our professional mobile mechanics come...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...