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OBD2 I/M readiness monitors

Discussion in 'General Automotive Discussion' started by mjz, Jan 8, 2020.

  1. mjz

    mjz Karting

    Aug 3, 2007
    114
    Houston, Texas
    Full Name:
    Michael
    I have an old ES300 Lexus (98,000 miles) year 2000. I use as a daily driver (when I am not driving my F430). I thought I would post an issue I haven't been able to resolve elsewhere on the Internet regarding OBD2 ready sensors not setting.

    The car runs great for 20 years old which is why I still have it. It just works - but this past month, two of the ready monitors will not set .... catalyst and evap monitor. There are no DTC codes or check engine light or pending codes. The fuel trims are all within range - even pretty good for an old car. The O2 sensors are relatively new (within last 1,000 miles) and report fine.

    Yet, I have driven this car hundreds of miles, followed all kinds of drive cycles (as specified by Toyota). What could be causing the ECU not to run the tests and complete? It bothers me that one has to guess on what is going on rather than the car's computer just tell me - throw a damn code - then I can fix it. I did notice a slight "chugging" on heavy acceleration (freeway entrance or quick start).

    (my wife has no understanding why I keep this car. If I can't resolve this soon - it's time to let go of it - even though it still works!)
     
  2. technom3

    technom3 F1 Rookie
    Silver Subscribed

    Mar 29, 2007
    4,083
    Phoenix AZ
    Full Name:
    Justin
    So I've been through this on a lotus exiege once. Which also uses Toyota engines and parts etc.

    What my issue was was the idiot who put the aftermarket exhaust on it plugged the precar o2 Into the post cat. And the post can Into the precat.

    The car never saw what it wanted (the exact opposite) and for some reason that didn't allow the evap to set. I
    h
    no idea of this is even possible on your car.

    However it took me about 4 long long solid days to figure that out.
     
  3. mjz

    mjz Karting

    Aug 3, 2007
    114
    Houston, Texas
    Full Name:
    Michael
    I checked the sensors and each one is where it is supposed to be - but I did notice when watchning the sensor readings that on one bank - the voltage variance is large - as low as 1.2 volts to as high as 4.6. The other bank is very solid around 3.3 v (+/- 0.2). I wonder if this is the culprit? and what is causing the sensor to swing wildly like this. It is a OEM Denso part - about 2-3 years old, few miles. Maybe it's just going bad. No check engine light or trouble codes whatsoever. But the car does "chug"/hesitate when I accelerate hard off the line (freeway ramp / green light). The readiness test still hasn't set, so something's wrong.
     
  4. technom3

    technom3 F1 Rookie
    Silver Subscribed

    Mar 29, 2007
    4,083
    Phoenix AZ
    Full Name:
    Justin

    Either swap them If you are tight on money. Or replace it.
     
  5. mjz

    mjz Karting

    Aug 3, 2007
    114
    Houston, Texas
    Full Name:
    Michael
    Money - no problem.
    My back - problem.
     

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