Jump to content

P0420 Code Issues

RaHCon

By RaHCon
in Ask A GM Technician

Recommended Posts

RaHCon Enthusiast

RaHCon

Posted
Posted

June 6-

1999 K1500 5.7l Suburban with 193K on it. Drove DFW to Denver. SES light came on once we got to Denver. Had local dealer read the code and it was "P0420 bank 1".

 

June 16 -

Cleaned K&N and MAS. Added 1/3 can SeaFoam to 1/4 tank gas. SES was still on.

 

June 18 -

Started truck this morning, day after order new cats, and SES light is now off.

Cancelled cat order.

 

June 27 -

Had AutoZone read the codes and it was still showing P0420.

 

Any ideas? SES is off, but system still showing P0420. Do I need to have this code deleted and see if it comes back? The truck is running fine, but I don't believe it will pass inspection unless this code is gone.

 

Thanks for any help/suggestions you can give.

GM-Tech Senior Enthusiast

GM-Tech

Posted
Posted

Never seen anything but a bad catalytic converter cause that DTC. The light will go off after the PCM has run the test on the converter and it passes three times, but the converter is probably just on the edge of being able to do its job.

 

Cats are not cheap, so if you want to clear the DTC and see if it comes back, you have nothing to lose, though I suspect you will see it again.

RaHCon Enthusiast

RaHCon

Posted
  • Author
Posted

Thanks for the quick response. I guess I was just hoping that the elevation changed had caused the system to get out of wack and now that it's home it would get re sync'ed.

 

I will get the DTC cleared and see if it comes back. I'll post what the results are.

 

Thanks again.

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.

  • Forum Statistics

    250.6k
    Total Topics
    2.7m
    Total Posts

  • Member Statistics

    342,993
    Total Members
    8,960
    Most Online
    President Roberto
    Newest Member
    President Roberto
    Joined

  • Who's Online   4 Members, 0 Anonymous, 1,042 Guests (See full list)

  • Latest Articles

  • Posts

    • bwiese
      upgrading speakers on 2026 std cab WT...

      By bwiese · Posted

      I don't wanna do major surgery/upgrades, behind-the-dash work, add amps, change radio etc. on my '26 std cab WT. On the WT, it has the base 7" IOR infotainment setup, and only two speakers (doors). Since I listen to classical, looked around for speakers that do well and dug thru reviews. Two-way speakers were found to be better than 3-way. So I've ordered a pair of  Infinity Reference REF-9632IX 2 way speakers.  [These may  or may not have been discontinued / succeeded by the 3-way ...9633 ones.]    These speakers are lauded for 3 ohm and 94db sensitivity spec so they'll work well for ordinary base car radios without amps and offer better performance (quality,  strength) than  default base paper-cone speakers. They'll be installed in a few days and I'll let y'all know what I think. Bill W San Jose      
    • RyanbabZ71
      RyanbabZ71's 2019 High Country

      By RyanbabZ71 · Posted

      Thanks!   Changed out the rear shocks today to Bilstein 5100s.  So far feel much better. The stock Rancho were wore out.  Lots of heavy hauling (2 moves, home renovations, etc).  Next up is new BFG tires Monday.  Cant wait the current tires have little to no wet traction and are super loud (hum)    
    • Snowcamo
      No high speed fans...

      By Snowcamo · Posted

      Ok, I got the all the codes. What do you all think would be a place to start?
    • Chuck FB
      Correct way to service 2024 l8t allison trans?

      By Chuck FB · Posted

      How about I just point to the factory pans stand pipe little drain plug and claim its a pan with a real drain plug !. I just couldn't swallow the fact that a Dorman pan which at this point is probably the only pan out there that fits the gas version truck cost that much up here in Canada so I decided initially anyway to skip it and see what I thought of pulling the pan method and down the road if I felt inclined enough then I would either install a drain plug kit in the factory pan if there is enough room for it, or have a bung welded onto it, or put an aftermarket pan on. The thing is if the pan is not pulled then the magnets in the pan can't be inspected and cleaned or if wanting to change out the filter. However of course it certainly would make the job easier to be able to drop the oil first before having to handle the pan if dropping the pan that go around was the goal.    I knew a guy locally that was doing custom field spraying years ago with a pickup pulling a ground driven sprayer, I believe it was a GM pickup with an automatic trans. He had a drain plug in his pan and would drop the oil out of it once a week and top it back up through the dipstick tube to keep refreshing a portion of the oil often and that made the transmission last far longer than had he done nothing. Soft fields pulling 500 gallons of water at the start of each mixed up sprayer tank batch and in low range sucking along. I imagine he got some tips from other custom sprayer outfits doing the same thing at the time and learning from their blown up tranny mistakes. Transmissions then had no lock up converter so would cook the crap out of the fluid slipping that much and it would not have been synthetic fluid either. 
    • KARNUT
      Gas Prices

      By KARNUT · Posted

      3.39 Kroger’s in Montgomery Texas. 

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...