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P-0171 & P-0300 codes

Discussion in '1st Gen. Tacomas (1995-2004)' started by jimpppe, Oct 10, 2015.

  1. Oct 10, 2015 at 6:12 PM
    #1
    jimpppe

    jimpppe [OP] Member

    Joined:
    Sep 23, 2012
    Member:
    #87536
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    Male
    First Name:
    James
    Connecticut
    Vehicle:
    SR5 6cly
    So, my 2000 with 198k and some change miles had the CEL come on. I checked the code and it was P-0171, Bank 1 too lean. I reset the code just to see if it would come back, and it did. I was wondering if I might get a bank 2 too lean code, so I left it for a week or so.

    Then I started noticing that it was having trouble accelerating. It was most noticeable after I left work. There is a slight incline to get out and some days it would just barely climb the hill. It feel like the transmission is slipping. I checked the transmission fluid and it is nice and red and to the full mark. (I changed the transmission fluid about 10k miles ago.)

    I rechecked the codes and now I'm getting both P-0171 and P-0300 random misfire. So, I set up Torque to graph the bank 1 probe 1 O2 sensor, the engine coolant temperature, the airflow sensor, and the fuel pressure sensor.

    The fuel sensor seems to be dead. I didn't see it come off 0 the entire drive into work. The airflow sensor seems to be almost dead too. It would just come about 1 line width off of zero. At a stop light I put it in park and reved the engine to 5000 rpm and the airflow sensor just barely came up.

    The engine temperature is fine, showing about 185 F.

    The O2 sensor looked to be pegged at zero, but when I would take my foot off the gas, it would monetarily peg high but then return to low. So, I think the O2 sensor is actually working, but it is just reporting what it sees.

    Anyway. Has anyone seen this type of issue before? It looks like I have 2 bad sensors, but I find it hard to believe that both failed at the same time. Of course, I am planning on looking at the airflow sensor, and maybe cleaning it. (I cleaned it last year.) and maybe testing it with a meter.

    Not sure what I can do about the fuel pressure sensor. I'll have to look it up in the manual to see what I can do.

    Do these 2 sensors share a harness or something like that that could explain both issues?

    Any advice will be appreciated.
     
  2. Oct 10, 2015 at 8:12 PM
    #2
    CodeSeven

    CodeSeven LOC: 33.781461, -115.867251

    Joined:
    Aug 20, 2014
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    Serge.
    Coachella Valley
    Vehicle:
    '00 Taco 3.4 4x4 TRD ( <3), '06 Taco Prerunner 4.0 (totaled)
    3 inch lift. bluetooth stereo. blue transparent skulls shift knobs
    paid version of torque? if not, get it. The free version sucks balls compared to the paid! and what obd2 interface are you using?

    this kinda sounds like a bad ECU. no sensors should be dead. see what your LTFT and STFTs say. should be above 25% if it's a true P-0171 (or 12.5 depending on if it's sensing 1 or both sides).
     
  3. Oct 10, 2015 at 8:49 PM
    #3
    CD20H

    CD20H Well-Known Member

    Joined:
    Oct 25, 2014
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    Ben
    North Texas
    Vehicle:
    2004 Double Cab TRD 4x4 Limited
    Magnuson Kompressor, OME lift kit, JBA Headers, junky Sony radio.
    PO171 Code. Just go ahead and replace the offending O2 sensor. They are normally replaced every 100k anyways as preventive maintenance. Your really close to being due.
    P0300 Code. Check your plugs and wires. Plugs are cheap, get a set of double ground and change them out.
     
  4. Oct 12, 2015 at 8:26 AM
    #4
    orangeoutlaw

    orangeoutlaw Well-Known Member

    Joined:
    Jan 30, 2014
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    #121849
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    48
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    Male
    NorCal
    Vehicle:
    2000 Taco ex cab
    2.5 sway-a-way coilovers, camburg 1" uniball uca's, Bilstien 7100's rear, Deaver j59 leafs, Solo Motorsports rear shock hoop relocation kit,Pro comp LA paz 16x8 matte black wheels with Toyo MT 305/70/16, 1.25" billet spacers, diff drop, Exedy stage 1 clutch, warn 9000, bent up bumpers, halo proj headlights, led tails and turns, snug-top, kicker comp 12, infinity kappa doors, kicker amps, painted frame, snug-top shell, yakima high roller bike racks
    p0300 coils plugs or wires
    p0171 o2 sensor
     

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