Code P0420

[tommy33]

Code P0420: Catalyst Efficiency Below Threshold Bank 1 comes on after drving at highway speeds.

I am assuming an O2 sensor. If so, which one? (Both?)

Thanks,

 

[tommy33]

97 Disco 73k miles. Major tune up done 4 months ago. New everything. Thanks,

 

[Hudy]

Well it could be a bad converter or a rear O2 sensor. You would need to look at what the O2 is reading to see if it has a wierd signal. They are usually around 430mV. A data display on a scan tool would be great if you have access to one.

 

[tommy33]

Thanks. I can get access to the scan tool.

 

[joey]

Could very well be the MAF sending a bad reading.... I would concider a good cleaning with a non-residue electrical contact cleaner.... remove from the Disco first and let dry for about 20 - 30 minutes before reinstall.

 

[tommy33]

Hey Joey: Did that a few months ago following your directions with electrical parts cleaner to stop the MAF code from popping up and it worked. Do you think it needs it again?
Thanks,

 

[joey]

anything is possible.... either that, or possibly drivers side is running a little rich. wouldn't hurt to run some seafoam or similar through the gas...

 

[tommy33]

I'll do both. Thanks,