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Old 03-13-2014, 03:34 AM   #1
Jcp123
 
Drives: '00 Echo
Join Date: Mar 2014
Location: E. Tx
Posts: 140
Hmmm...P0420, eh?

Hey guys...new here. Technically I do not have a Yaris, but rather a 2000 Echo. Hey, we all are in the 1NZFE family, right? I thought I might post here since there was some good technical discussion on this code in my yahoo search.

Anyhow, this Echo was inherited from my wife, who in turn inherited it from her parents. Currently it has 240k miles. Naturally she was vague about maintenance history but said it definitely received regular oil changes. Owing to the fact I had to replace the absolutely decrepit original spark plugs at about 195k, I tend to believe it had nothing but those regular oil changes. I had some overheating and driveability problems cured by a MAF sensor cleaning. I also got my first P0420 coded around this time. The cat was duly replaced and for about 2 years and 30k miles, all was good. It still drives strong with good power and fantastic gas mileage in the 39mpg range for my commute. I run nothing but Texaco or Chevron since they carry Techron.

About 6 months ago, P0420 started to reappear periodically. It has gradually started to appear more often, about once per week. I just got done with an attempted cleaning of the IAC...IAC is dead. Cleaned out a lot of gunk while I was at it. But on my first full day of driving, about 35mi total, it popped up no less than four times.

At this point, I am at a bit of a crossroads. It was a super cheap cat which was put on - $130 installed, so I guess I wouldn't be surprised if it had failed. I am also pretty sure (actually almost positive) that the O2 sensors are original as well. O2 sensors are hardly immortal either.

I run an UltraGauge and can monitor my O2s. Voltage seems to stay under 1v on up- and downstream sensors. But fuel trims trouble me a bit more. Long trim seems fixed at 7.81, short term seems to vacillate between -1 and +4. I was taught that -10 to +10 is a normal range, but also that they should generally add to a sum close to zero? I.e. with a long term of 7.8, should I not see short terms generally stay around -7 to -8 but for throttle and/or load changes? Constant throttle seems to yield short terms of about +1 to +2.

Technical maybe...but I would like to know what I am facing. This sounds like it could go either way, O2s or cat. I'd kinda rather put the money back into my other car...it's a classic and is appreciating as opposed to this abused little workhorse. But I hate to think this car is giving up the ghost. I have actually gotten to like the car and triple the gas mileage is...tempting...and honestly the car is pretty damn reliable.

Last edited by Jcp123; 03-13-2014 at 04:10 AM.
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Old 03-13-2014, 08:28 AM   #2
CTScott
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How much of a fluctuation do you see for the voltage on the O2 sensors? Typically they will move around quite a bit and when the sensors fail they will just sit at a single value.
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Old 03-13-2014, 08:08 PM   #3
Jcp123
 
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I will have to observe the o2 voltages a bit more closely...Will report back!

Thanks for the reply
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Old 03-13-2014, 08:36 PM   #4
malibuguy
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Check the donut gasket at the manifold. As it is acts as the flex joint they wear out. It may be leaking just enough to throw the light but without it being obvious.

Typical standard replacement converters are low quality...unfortunatly...especially if it was $130.
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Old 03-14-2014, 05:39 PM   #5
Jcp123
 
Drives: '00 Echo
Join Date: Mar 2014
Location: E. Tx
Posts: 140
Thanks, I will have to take a look at the flange gasket!

Alright, took a look at the voltages. Upstream vacillated regularly, between .1 and .8 volts. 80% of its time was spent between .15 and .7 volts. The downstream unit was happier between .45 and .65v.
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