check engine light, bad news...

**beason** · 07-04-2009, 05:28 PM

I got a check engine light on my truck. ran it up to autozone to run the code, and it came back p0420.

catalyst system efficiency below threshold - bank 1

probably cause
air leak in exhaust before rear h02s
Af sensor error
fuel system fault
faulty catalytic converter

Now, im pretty sure its the MAF, since when i had problems when the truck died, someone told me to clean it. I cleaned it using MAF cleaner, but i think that damaged it.

I feel this would be the most logical outcome.

Has anyone else had this error code?

Autozone quoted me over $200 for the MAF.

The previous owner removed the air box and installed a cone filter on the end of the tube, i would like to put an air box back in, would it be better to just get an aftermarket setup? do they come with MAF's?

titanss · 07-04-2009, 07:40 PM

If you used the CRC Mas Air Cleaner it did not hurt the MAF, i have used it on my Titan. This is a common code, look for leaks before the 02 sensors. There have been post on the cats coming apart on these trucks.

**beason** · 07-04-2009, 11:36 PM

where would i begin looking for leaks? in the exhaust?

**walleeme** · 07-05-2009, 12:52 AM

Exhaust is part of the emissions warranty. I think o2 sensor should be too.
Should be covered for 8/80.

Just so you know.

titanss · 07-05-2009, 07:22 AM

Look for black soot around any flange, clamp or 02 bung. The exhaust leaves this soot when it is escaping the pipes.
If your still under warranty, let the dealer worry about it.

**beason** · 07-05-2009, 08:54 AM

its an 06 with 60k, but i got no info about warranty when i bought it. i can just take it to the dealer and they will check it out?