OBD-II "PO420" Code???

[ortred]

The other day on a two hour drive, my check engine light came on; took it to Autozone to have it checked; his scanner popped the code “PO420 – Catalyst System Efficiency Below Threshold (Bank 1)". I had him check for other codes, but that was the only one, so I had him clear the code, (and the check engine light) to see if it happens again. Is there a bunch of possibilities that would produce this code or does it mean one problem in particular? If it happens again I would just like to know where to start troubleshooting or if I have to take it somewhere for the repairs.

Thanks all,
Jason
1996 Ford Explorer / XLT / V6 / 66,000 miles

 

[Bashman]

Usually indicates a bad catalytic converter or bad post cat O2 sensor. If the code comes back, I would change the sensor and clear the code again.

 

[dan leon]

My 96 xlt did the same code at 110k miles. I replaced the post o2 sensor and the code has not since reappeared.

 

[Runnin'OnEmpty]

Jason, the wire harness to the after cat sensor travels directly over the cat, and is not restrained. The wires tend to sag down and get burned by the cat, so check the wiring harness and plug first......

 

[ortred]

Thanks for all the help! So...

My plan of attack is as follows:

Check the wiring harness for a burnt connection. If that is ok, wait until the code returns and replace the post cat O2 sensor and clear code again. If the code returns after all that, replace the cat.

Thanks again guys!

PS - Update me if you think of anything else; I will let you know what I find out.

 

[dan leon]

I would replace the pre-cat o2 sensors before replacing the cat's. I have been told that the pre-cat sensors last about 60k miles and then should be replaced.

Dan