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DIY upstream A/F sensor replacement write-up P2238

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by BuyJapanese, Mar 11, 2022.

  1. BuyJapanese

    BuyJapanese Member

    Jun 12, 2019
    2005 Prius
    There are several threads and videos on this, but none that I found very helpful, so here's my contribution.

    First, tools: minimum required tools are a pointy flathead screwdriver, 10mm and 14mm sockets w/ratchet, 3-6" extension, a long-handled ratchet, breaker, or cheater pipe, and a special o2 sensor removal tool.

    I highly recommend getting an 18" flex-head ratchet vs using a breaker (limited positioning) or a cheater pipe (hard to leverage in tight spaces). This should enable you to avoid removing the exhaust manifold heat shield, and will be helpful even if you do take that off.

    I also highly recommend this o2 tool, 66750B from toolsource. It fits perfectly without being unnecessarily long.

    Other tools I used:
    1. shop light
    2. penetrating oil
    3. power ratchet
    4. shop rags
    5. jack & jackstands if you're also doing the downstream o2 sensor
    6. Stretchy magnet and stretchy mirror
    7. Small impact driver
    8. magnetic parts tray for the little bolts

    Step 1: Screwdriver to pry cap off top of bolt from driver-side wiper, 14mm bolt, then remove driver's wiper.

    Step 2: hood open, two more 14mm bolts for passenger wiper


    Step 3: Remove plastic trim over wiper motor. Two plastic push pins, then lift it in the middle at the seam. (I'd already removed it in this pic)


    Step 4: 8 bolts to remove wiper motor tray (I think I missed one in this image). No need to remove wiper motor from the tray first, but I guess it makes access easier for a couple of the bolts. All 10mm. Two are long, it's easy to place these on reassembly because they're the ones in back-center and back-drivers side that go into rubber bushings. Disconnect the motor wire. ALSO ideally disconnect the electrical box mounted to the wiper motor tray (2 more 10mm) and that wire in two places where it's pinned into the wiper motor tray. Remove the wiper tray completely.


    Step 5: now you have access. Get your tool in place. Start finagling your ratchet, long ratchet if you have it, or breaker bar/cheater pipe. Good luck! If you just can't get enough room to get leverage to break it loose, you can carefully remove the exhaust manifold heat shield (4 bolts that are likely to break or round out) to give you more options. Spray these bolts with penetrating oil, and remove the two at the top first as they're likely less rusty. Maybe you will choose to bend back your heat shield instead of tackling the bottom bolts. The top two are vertically oriented, invisible behind the engine at the top of the exhaust manifold. 1F764FA0-C335-4943-A7D4-45525A451B2C_1_105_c.jpeg



    Once you break the sensor loose, follow the wire harness up to the connector. The connector is stuck between the engine and the inverter, under the inverter coolant reservoir. It's very hard to access. I recommend getting your left hand onto the wires, and using your right hand a long screwdriver to push down on the locking tab on the female end that's mounted to the bracket. Push that locking tab down and pull on the sensor wires (normally you should pull on connectors, not wires, but this is the old sensor going in the trash so pull away).


    With the sensor unplugged, finish unscrewing it. Get some anti-seize on the threads of the new one (avoid touching or getting anti-seize on the business end of the new sensor). Get it in there, handtighten it to avoid cross-threading, then tighten with the tool and your ratchet. Now plug it in. Continue reassembly. When you're done, take a test drive and make sure to test the wipers.

    SFO and JC91006 like this.