XPost: sci.electronics.repair, alt.home.repair   
   From: kludge@panix.com   
      
   In article , mike   wrote:   
   >How could 50 to 100 clearings of the OBD codes (using a dumb OBD reader)   
   >cause the catalytic I/M readiness monitor to set after months of not   
   >setting?   
      
   It cannot.  But the fact that you've got 50 to 100 clearings of the OBD codes   
   makes your general maintenance process very suspect.   
      
   >[1] The check engine light has been on, on the dash, almost constantly   
   >[2] Mostly when I looked, it would be P0420 bad cat pending & set codes   
   >[3] I've been going through this regimen now, for about five or six years   
   >[4] I didn't need smog for more than a year so I didn't worry about codes   
      
   What this means is that the O2 sensor downstream of your converter is   
   reading an incorrect value.  This could mean your converter is bad, or   
   maybe that the O2 sensor is bad, or maybe that the connector is bad.   
      
   If other codes were set too, it could have been all kinds of other things.   
   If you're seeing incorrect values on both pre and post converter   
   sensors, you'll see other codes, and that could be the result of all kinds   
   of misfiring issues or mixture control issues.   
      
   >[5] When it came within months of smog time, I cleared the OBD codes   
   >[6] Mostly either the code comes back or the readiness monitor won't set   
   >[7] But once in a while, the readiness monitor does set so I rush to smog   
      
   Have you considered actually finding and fixing the problem instead of   
   constantly resetting the error?  You're not doing your engine or your   
   gasoline bill any good this way.   
      
   >[8] I did that - it passed smog - but failed for a hose in bad condition   
   >[9] I painted the hose black so that it would look like it's brand new   
      
   Wow, with maintenance like that it's a wonder your car runs at all.   
      
   >[10] But then for another month I couldn't get the readiness monitor to set   
   >[11] At one point, I accidentally added gasoline with water (long story)   
   >[12] The car ran like hell for an entire gas tank until I refilled it   
   >   
   >After that, it passed smog and for months now, no codes.   
   >What happened?   
   >I have no clue.   
      
   Maybe the converter was dirty and all the steam cleaned it out.  Maybe you   
   had a fouled plug which was causing a misfire and the steam cleaned it up.   
   Maybe you had a bad vacuum hose and the warmer weather caused it to seal up.   
      
   Since you didn't actually find the problem when you had the code coming up,   
   and you made no attempt to do actual diagnosis, it's hard to tell after the   
   fact.   
      
   >Within a mile, the engine would stumble and I'd clear the codes and the   
   >engine would run fine for another mile, and then it would stumble, and then   
   >I'd clear the code and it would run fine for another mile, and so on.   
   >   
   >This I did for at least a hundred, maybe two hundred maybe three hundred   
   >times during the watery gas stage - but - miracles to happen I guess   
   >because after that, no codes and, get this, the readiness monitors all set.   
      
   As my father always said, "machines that fix themselves always break   
   themselves again."   
      
   >Can it be that there is some kind of multiple instance "persistent memory"   
   >inside one of the engine computers that I finally wiped out by clearing the   
   >codes hundreds of times in a row?   
      
   You are too fixated on the codes popping up and making no attempt to ask   
   WHY the codes were popping up and what was actually going on.  Stop worrying   
   about the damn codes and start worrying about how the engine is running.   
   --scott   
   --   
   "C'est un Nagra. C'est suisse, et tres, tres precis."   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)