Hey guys, i was just driving to school and stopped for construction when the check engine light came on. got to school and checked the code and it is P0420. i checked the code index on the forum but it didn't help much it just said something to do with the catalytic converters. can i get a better discription of what this code means and what i'm going to have to do to fix it? I live in a county where there is no emissions testing so would cutting the cat out and replacing it with a piece of pipe be an option? thank you all for your response.

 

basically it means your emmissions system is not performing up to the standards that are programmed into the system. you can cut it out but that wont fix the check engine light. whats happening is the pre cat o2 sensor is telling the computer readings and then the post cat is telling it readings that dont meet the set standards.... if it was me i would replace the cat and the o2 sensors

 

its an o2 sensor code, i would start by clearing the code and see if it comes back, someitmes water gets into the wiring and can trip the code. if it stays off no problem

then i would pull the post cat o2 sensor and replace that and clear the code again

if it STILL comes back then look into replacing the cat. the only reaosn i dont jump to the cat is bc they are EXPENSIVE!!!!!!!!!! and there are many equally like (sometimes more likely) culprits that are MUCH cheaper, start with the stupid/cheap stuff first and go from there.

 

thanks guys, i'll reset the pcm tomorrow and see what happens. it has been raining for 3 days straight so it wouldn't surprise me if it got wet. i also noticed my gas mileage has been really ****ty this week but it's probably just my right foot.

 

you can fix that mpg problem with a brick



(put the brick UNDER the go pedal )

 

P0420 1/1 Catalytic Conv Eff

Ya, could have been the water.

 

Symptom:
P0420-1/1 CATALYTIC CONVERTER EFFICIENCY
When Monitored and Set Condition:
P0420-1/1 CATALYTIC CONVERTER EFFICIENCY
When Monitored: After engine warm up to 147 deg. F, 180 seconds of open throttle
operation, at a speed greater than 20 mph, with the engine at 1200-1700 rpm and MAP
vacuum between 15.0 and 21.0 inches of mercury (Hg).
Set Condition: As catalyst efficiency deteriorates, the switch rate of the downstream O2
sensor approaches that of the upstream O2 sensor. If at any point during the test the
switch ratio reaches a predetermined value a counter is incremented by one.
POSSIBLE CAUSES
CATALYST EFFICIENCY DTC DOES NOT REOCCUR
ENGINE MECHANICAL PROBLEM
EXHAUST LEAK
CATALYTIC CONVERTER 1/1
UPSTREAM O2 SENSOR OLDER THAN DOWNSTREAM O2 SENSOR
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRB, read the DTCs.
Is the DTC SPECIFIC GOOD TRIP counter displayed and equal to zero?
All
Yes ® Go To 3
No ® Go To 2
2 At this time the Catalyst Efficiency Failure does not exist or is an intermittent
problem.
With the DRB, read the FREEZE FRAME data.
With this screen, attempt to duplicate the condition that has set this fault.
While using FREEZE FRAME pay particular attention to the fault setting conditions,
such as speed, temp, load, and map vacuum.
Does the Catalyst Efficiency DTC Reoccur?
All
Yes ® Go To 3
No ® The Catalytic Conveter Efficiency Failure no longer exists.
3 Check the exhaust for excessive smoke from internal oil or coolant leaks.
Is there an oil or coolant consumption condition present?
All
Yes ® Repair engine mechanical condition as necessary and replace
Catalytic Converter.
Perform Powertrain Verification Test VER-2.
No ® Go To 4

 

hahaha but then again i didn't buy the 5.9 for good gas mileage so i better stop bitching. but anyways i reset the pcm this morning so we'll see if the light stays off or not. suppose to be sunny for atleast a week straight so if it comes back on i'll know for sure that it wasn't because of the water.