99 Sienna O2 sensor change (all 1mzfe engines)

polifrog

Temporary Note for the month of October:  If you find the post below useful please consider purchasing a round of popcorn from the link above for yourself , for the scouts and my son who's idea it was to put this on polifrog. 

Thanks 

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This summer we left our home in Eden for Charlotte. There we stayed with my father for a couple of days before our trip "out west" was to begin. We did this for a couple of reasons. First we felt it was wise to have a trial run before the trip and second I had a the couple of things to complete on the camper.

The trip began at around 7PM after 5:oo traffic had died down. We were 15 minutes into the trip when the check-engine light flashed on. I considered ignoring it as the light generally only indicates an emissions issue. My father had an OB2 scanner back home, though, so we turned around to take advantage of the tool. Ultimately knowing what was wrong would ease my mind.

With the OB2 scanner in hand I was able to divine just what the check-engine light was complaining about. It read O2 sensor 1, bank 1.

I found this service bulletin from Toyota concerning which bank is 1 and which is 2.

After a little research I found that bank 2 was next to the bumper and that bank 1 was next to the firewall. Sigh. That would make the O2 sensor difficult to get to and much more likely that I would ignore it. Later the repair confirmed that bank 1 was near the firewall, as that is the O2 sensor that I replaced and after which the 'check engine' light stayed off.

Again, we left my dad's house on the start of a two month road trip, only this time we had the OB2 scanner with us and a permanently illuminated check-engine light. The light remained on until today.

The fix...



I put the Sienna on ramps to get under it. Once under it I was able to get my first visual on the O2 sensor. It was located near the rear part of the engine cradle and with the various power steering lines, power steering rack, exhaust, and driver's half shaft it was difficult to reach. I found it even more difficult to uncouple the lead to the sensor as it was just outside my reach with my arm wedged between the engine cradle and transmission.





After failing to disconnect the lead from underneath I attempted it from above. At first glance this seemed impossible, but I found a hole to the right of the intake plenum that allowed access to the connector. After familiarizing myself with another similar more accessible connector on the A/C dryer I was able to disconnect the O2 sensor with one hand from above the engine. This was done entirely by touch as I had no way to see the connector from above.



Now, all that remained was to remove the sensor. I got back under the Sienna and found that my O2 sensor socket was useless due to the O2 sensor's tight living quarters. I relaxed on the driveway looking up at the sensor wondering what to do when it dawned on me that an open ended wrench (spanner) would work just fine. Simple. Sometimes I'm slow.



Assembly was the reverse with the only difficulty being, once again, the connector. I found that I could hold both ends of the O2 connector in my left hand after reaching it from above as before. With a little fiddling I was able correctly position the two ends of the connector and get an audible click once they were fully engaged.

Job done.


Update 1:
I purchased the replacement O2 sensor off of Ebay for around $30. Original but used. New ones can be quite expensive....I rolled the dice on this purchase, but it worked out for me. Others may not be so lucky.



Update 2:
From the comments below

I just finished replacing the front (2) O2 sensors on my '99 Toyota Sienna. Here is some useful info for anyone who comes across this while googling.

Bank 1, Sensor 1(back of the engine, by the firewall):
Toyota / Lexus part number: 89467-41021
Denso equivalent part number for this sensor is: 234-9007


Bank 2, Sensor 1(front, by the radiator):
Old Toyota / Lexus part number: 89467-48010
New (improved) Toyota / Lexus part number: 89467-48011
Denso equivalent part number for this sensor is: 234-9009

(These sensors) are OEM, exact match sensors. While cheaper universal O2 sensors may work, they are not guaranteed to clear your check engine codes.

Update 3: (California Models)
From the comments below:

Here's one tip from my end. Find out whether your car is california model or 49-state model. Their sensors are NOT the same. If you don't know, easiest thing is to open up the hood, take a look of that front sensor, copy down its toyota part number and do denso cross reference. Here's one you can use:

http://www.benitomo.com/CATALOGOS/Denso/2008_DENSO_O2_Catalog_-_Cross_Reference.pdf


If you have a 49-state 2000 Sienna, here's denso sensors that fits perfectly:

front ones(before cat, need 2) - denso 234-4622

rear(after cat) - denso 234-4623

I ordered it from Amazon, best pricing and fast shipping.

Hope this helps.

out