codeman061988

Hello everyone,

New guy to the forum here...

I just had an OBDII emissions test done yesterday and ended up failing. The reason was for a the EVAP system giving a "Not Ready" status and the Heated Cat, Secondary, and Air Cond. systems returning "No Signal".

The guy who ran the test explained that the EVAP system returning "Not Ready" may have something to do with the other systems returning no signal.
The scan returned to fault codes... P0420 and P0141.

I'm not sure what the EVAP system not being ready has to do with the O2 systems not even returning a signal.

I can navigate my way around an engine enough to replace sensors and solenoids if necessary but I wonder how I could figure out what to replace or repair in this case?

If the root of the problem is due to the EVAP system, should I replace the purge valve on the canister or a sensor? Should I also consider replacing both up and down stream O2 sensors?

Thanks,
-Cody

tech2

the evap monitor will not run to completion due to the other dtc that have set. It will be withheld until the other dtc have run and passed. repair the faults for the dtc that have set first.


pretty sure p0420 is a low cat efficiency dtc and the p0171 is a either a system lean or rich dtc.


all data or michell on demand will have service information to diagnose these fault codes.

codeman061988

Okay so its cause an effect in that sense then.

I guess I just wanted to be pointed in the right direction so I'm not spending needlessly on parts that don't need to be replaced.

I suppose the cat. needs to be replaced for starters. My pickup has around 220,000 miles on it so it may be the end of it's life. As far as fuel mixture, I may have to research that a bit a figure out how to adjust something like that.

I've got a subscription to Alldata diy so I'll see if I can find out how. It's a handy resource.

tech2

I would clear all the dtc and diagnose the ones that return. The p0420 monitor should not run and set a dtc if fuel trim codes have failed

codeman061988

I'll probably take that approach and see where I am. I'll update when I get a chance to do this.
I appreciate the input.