Toyota Sienna Bank 1 Oxygen Sensor: Replacement Thereof

So there we were, on our way to the Dutchess County Fair when I noticed the Check Engine light glowing beyond my right hand on the dashboard. We decided to not stop at the fair, drove through Rhinebeck, and returned home without turning the engine off.

The last time that light came on, my Shop Assistant and I were on our way to Cabin Fever in York PA one Friday afternoon in mid-January. The Mass Air Flow Sensor had just failed, rendering the car un-driveable: the engine ran so poorly we barely got off I-81 to drift into a parking lot. Although the local Toyota dealer was just across the road, I replaced that sensor on Monday morning in the Autozone parking lot, half a mile down the road, at 19 °F in a stiff wind with inadequate tools; said Toyota dealer being useless like tits on a bull during the entire weekend.

After the obligatory research, I put the van up on jack stands, crawled underneath, and discovered that the Bank 1 Oxygen Sensor lies behind & below the transverse-and-rotated engine, directly above and front of the chassis cross-support strut, where it cannot be seen or touched from any position. That’s why there are no pictures: there was no room for a camera and nothing to see.

I had to buy a 3/8 inch breaker bar, as the sensor position lacked clearance for a socket wrench, a U-joint, a T-handle, or a step-down adapter from my 1/2 breaker bar behind the special 22 mm Oxygen Sensor Socket. I eventually got the sensor loose and unscrewed it one painful eighth of a turn at a time, with the exhaust pipe preventing a full 1/4 turn, removing and reseating the breaker bar with my fingertips for every single one of those increments.

I deleted all over Toyota’s censored for quite some time thereafter…

It’s been a couple of weeks, the Check Engine light remains off, and I hereby declare victory.

11 thoughts on “Toyota Sienna Bank 1 Oxygen Sensor: Replacement Thereof

  1. How did you decide to replace the oxygen sensor instead of the reverse turbo encabulator or some other part?

    1. Drove the hulk to the local Autozone and asked them to read out the diagnostic data behind the Check Engine light. They looked up the failing part, then I laid a pair of C notes (well, really, a credit card) on the counter in exchange for the sensor… easy!

      That said, it was much easier than with the MAF sensor failure. That spat out a torrent of failing parts, but the nice man behind the counter suggested the MAF was the real failure. The diag codes also tagged the Bank 2 Oxygen Sensor (the easy one, in plain view in front of the engine) and IIRC I replaced that one when we got home.

      One thumb up for the diagnostic codes…

  2. And people wonder why I’d rather help them with an old slant-six engine in a huge car. That sounds like the opposite of fun.

    1. Yeah, you could actually see all the parts and maybe even climb in beside the engine to work on ’em. The front end of the van seems pretty well shrink-wrapped around the engine!

  3. I’m just about to do N’s, got the 22mm wrench yesterday. Any hints on getting it loose? In my case it’s inside a shroud around the second catalytic converter, so that has to come off, and my attempts to get the bolts loose have met with complete failure so it looks like I’m going to have to drill them all out. Sigh.

    1. The threads on both exhaust sensors were in perfect shape, which is said to be atypical. Hosing the threads with penetrating oil seems to be the proper first step, although I didn’t do that. Perforce, you’d be unable to drive the car between dousing the threads and replacing the sensor, plus it’d stink to high heaven for a while thereafter.

      The half-inch breaker bar and plenty of muttering sufficed for the front sensor. The rear one was much, much worse: no room for the big bar, bad access, cramped quarters.

      Use the biggest breaker bar that fits, make sure you apply lefty-loosy torque, and have at it!

  4. This reminds me of my bright idea to replace the intake manifold gasket myself to save some money on my Saturn SL2. All of the bolts were difficult to reach (even after removing the hood) and one required fabricating my own socket extension. But I got ‘er done, the diag codes all cleared, and I saved myself a few hundred bucks. My hat is off to you sir.

    1. and I saved myself a few hundred bucks.

      You can tell why the shop charges so much: they don’t want to do it, either. I suppose the book rate takes some of the sting out of it.

      I always joke about putting a few hundred bucks in the General Fund cookie jar after such a repair. It’s stale, but very, very true…

      1. I actually had a mechanic complain to me that I did all the easy(ish) stuff myself, and left him with the horrible jobs (like replacing a heater core).

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