Question about 2001 Toyota Camry
The catalytic converter was replaced. I still can't pass the emissions test.
It is failing at READINESS. Basically is saying that the car need to be driven for 100 miles, after I can take the test again. I drove more the 100 miles, in fact I put about 1500 miles in two weeks, and still saying "READINESS = FAIL".
The system has to complete a certain number of drive cycles to complete the system readiness function, this is a mixture of stop and go, highway and idling, I admit it should have cleared by now, but try to do a mixture of driving, just highway won't do it, it should complete soon, if it doesn't then there is a problem that will have to be diagnosed.
Posted on Nov 10, 2008
The P0420 code, usually associated with a weak cat converter, is in fact often caused by an ageing (weak) downstream O2 sensor. On both my cars at around 150K miles replacing the downstream O2 sensor was all that was needed to clear the code. No cat replacement was necessary. If one actually spends some time reading the diagnostics procedure for this code, they will find that the O2 sensor diagnostic is the first thing to do before replacing the cat converter. The downstream sensor, the one after the cat converter, gets "lazy" with age. This means that it no longer produces voltage signals as it used to. The result is that the voltage swings that come out of it begins to follow very closely the voltage that is generated by the upstream O2 sensor. When this happens, the car computer thinks the cat converter does not do its job (which might as well be the case too, but the O2 sensor is the first thing to try). With a code scanner with live data stream you can see the voltages coming from the O2 sensors. Check-out my write-up on the 2002 Toyota Prius cat converter replacement on http://www.pbase.com/kocho/exhaust_prius
- I got some details there. And see my comment for Dennis above here too
Posted on Nov 11, 2012
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