1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Should I change my O2 sensor at 252k?

Discussion in 'Gen 2 Prius Main Forum' started by SRQ, Mar 11, 2023.

  1. SRQ

    SRQ Member

    Joined:
    Jan 25, 2013
    148
    53
    0
    Vehicle:
    2008 Prius
    Model:
    N/A
    Never changed it, and wanted to see if it's worth changing the sensor after 252k without a replacement. No codes.
     
  2. Elektroingenieur

    Elektroingenieur Senior Member

    Joined:
    Jan 8, 2017
    2,515
    3,253
    9
    Location:
    California
    Vehicle:
    2016 Prius
    Model:
    Three Touring
    I see no reason to incur the costs or risk of maintenance-induced trouble from preventive replacement of the heated oxygen sensor.

    The sensor and its heater circuit are both monitored by the engine control module (ECM), which would set a diagnostic trouble code and turn on the malfunction indicator lamp (check engine light) in case of a failure. The car would still be drivable, but with the ECM running in open loop control mode without feedback from the sensor, its emissions might be higher and fuel economy lower until repairs were made.

    Let’s apply Nowlan and Heap’s Reliability-Centered Maintenance precepts (United Airlines, 1978, p. xvii):

    ▸ Scheduled maintenance is required for any item whose loss of function or mode of failure could have safety consequences. If preventive tasks cannot reduce the risk of such failures to an acceptable level, the item must be redesigned to alter its failure consequences.

    ▸ Scheduled maintenance is required for any item whose functional failure will not be evident to the operating crew, and therefore reported for corrective action.

    ▸ In all other cases the consequences of failure are economic, and maintenance tasks directed at preventing such failures must be justified on economic grounds.
    Clearly we’re in the third situation: if the sensor were to fail, the car would still be safe, and the failure would be indicated to the driver. Since the cost to replace the sensor would be the same, before or after a failure, which might not occur at all during the car’s remaining service life, there’s no economic justification.
     
  3. highmilesgarage

    Joined:
    Jul 28, 2022
    232
    87
    0
    Location:
    Kansas City
    Vehicle:
    2007 Prius
    Model:
    Touring
    it will not leave you stranded if they fail, worst a check engine light or rough running. Change it when you got a code.
     
  4. mr_guy_mann

    mr_guy_mann Senior Member

    Joined:
    Sep 3, 2020
    3,206
    1,339
    0
    Location:
    NJ-USA
    Vehicle:
    2006 Prius
    Model:
    Four
    I might look at fuel trim numbers in scandata. My 2006 at 200k is still running near 0%.

    Maybe mode 06 data from the OBD2 monitor results. See how close the O2 tests are to their "fail" points.

    For the most part as stated, the ECM will "let you know"when you need to replace the A/F or O2 sensors (at least 95% of the time).

    Posted via the PriusChat mobile app.
     
  5. SRQ

    SRQ Member

    Joined:
    Jan 25, 2013
    148
    53
    0
    Vehicle:
    2008 Prius
    Model:
    N/A
    Perhaps using a 45 year old paper intended for aircraft maintenance to apply to... a Prius is not the best practice.

    Especially since there have been FAA AC's and other regulations that may have been released since then.
     
  6. Elektroingenieur

    Elektroingenieur Senior Member

    Joined:
    Jan 8, 2017
    2,515
    3,253
    9
    Location:
    California
    Vehicle:
    2016 Prius
    Model:
    Three Touring
    Reliability-centered maintenance is a concept that’s now applied successfully in many industries. I cited the original report because it’s well-written and freely-available, and to properly credit its authors. Did you read it, or even just the abstract? Did you notice that an objective of the report was to be “a guide for application to a wide range of different types” of complex equipment, not just commercial airplanes?
    I’m well aware of MSG-3 and later developments; the basic principles are the same.
     
  7. highmilesgarage

    Joined:
    Jul 28, 2022
    232
    87
    0
    Location:
    Kansas City
    Vehicle:
    2007 Prius
    Model:
    Touring
    it's very common for the heater circuit to fail on the OEM O2 sensors, the oxygen sensor itself is still working even at higher miles. My 07 Camry Hybrid still has the original front O2 sensors at 202k miles (16 yrs old) and I just replaced the rear O2 because of a failed heater circuit. Did it affect my driving or leave me stranded if I just left the heater circuit not addressed? nope.
     
  8. ColoradoBoo

    ColoradoBoo Senior Member

    Joined:
    Jul 19, 2019
    903
    593
    4
    Location:
    Monument, Colorado USA
    Vehicle:
    2017 Prius
    Model:
    Two
    I agree with the folks who say, no, it's one of the items that are on the "if it ain't broke don't fix it" list.

    I do replace some things at 10-years because I know they are on the verge of going bad....spark plugs; PCV valve and the little hoses around it; gasoline refill cap; any coolant hoses that aren't looking good; serpentine belt if it hasn't been replaced; and radiator cap. (They get rusty inside after about 10 years.)

    Good job taking care of you car....so many these days don't even give it a second thought. (I see way too many driving around with a near-flat tire or lights/blinkers out.)
     
  9. SRQ

    SRQ Member

    Joined:
    Jan 25, 2013
    148
    53
    0
    Vehicle:
    2008 Prius
    Model:
    N/A
    Fair enough; thank you for taking the time to respond in that manner, it was very on-brand for this forum, despite being a lot more than required.

    I'm the guy that flies the things I figure you create, I have to know enough to know when to start thinking about preventative maintenance.

    Big thanks! As a fellow bag-wearer, I think you understand why my vehicle is still on the road, and barely halfway thorough its useful life!
     
  10. douglasjre

    douglasjre Senior Member

    Joined:
    Sep 13, 2008
    1,743
    613
    0
    Location:
    Orlando, FL
    Vehicle:
    2010 Prius
    Model:
    ----USA----
    Aaaaaand commence blocking srq lol