Best Answer

Three O2 Sensors. one in each exhaust manifold before the catalytic converters. then one after the cat.


How to replace your downstream O2 sensor (the one after the cat, that's threaded into the exhaust pipe).

You need a Bosch 13353 Oxygen Sensor. This sensor IS an EXACT fit/replacement for your downstream sensor on a 1998 (1st gen) Toyota Sienna --- down to the wire holding clip.

The downstream sensor's connector on a 1998 (1st gen) Sienna is located under the front passenger seat.

*Remove the 4 - 14mm bolts holding down the seat.
*Prop the seat upward.
*Pull back on the carpeting slit to reveal the connector.
*Pinch the connector to remove the female end of it.
*Use a needle nose pliers to pull up and remove the rubber grommet from the floorboard, then push it down through the hole.
*Jack up the right front (behind right front wheel), then use a jack stand for safety.
Note: Make sure the exhaust pipe is well-warmed to the touch - for easier removal of the old sensor.
*Use a 22mm box wrench (counter-clockwise) to remove the old downstream sensor from the exhaust pipe.
*Install the new sensor (already contains anti-seize compound). Do not overtighten.
*Snake the wires/connector up through the floorboard.
*Use your needle nose pliers to pull the grommet up through the floorboard, then massage it into place with your fingers.
*Click the female connector into place.
*Re-install the seat.

Hey! You just saved big $bucks$ by doing this yourself.

Here is a link to a detailed post with pics of an O2 sensor replacement. The one replaced was between the engine and the firewall. Just cut and paste the link below...


User Avatar

Wiki User

โˆ™ 2009-11-05 00:26:43
This answer is:
User Avatar

Add your answer:

Earn +5 pts
Q: How many oxygen sensors are there in a 1999 Toyota Sienna?
Write your answer...

Related Questions

How many oxygen sensors are on a 1999 Toyota Tacoma?


AC light blinking 1999 sienna?

what cause the ac light to blink on a 1999 Toyota sienna

How many miles can a Toyota Sienna get in its lifetime?

My 1999 sienna has 234,000 and no serious problems yet!

How much is tune up for a 1999 Toyota Sienna?


Fuel light Toyota Sienna?

My family has driven three hours on empty in a 1999 Toyota sienna. We were driving on the mountains, and we thank God to be alive.

What does it cost to replace a catalytic converter on a 1999 Toyota Sienna?

How much does it cost to replace the catalytic converter on a 1999 Toyota Tacoma

Where is the starter located on a 1999 Toyota Sienna?

i star my Toyota sienna van and hear some noise when i turn off it the estarter still egage, wha is wrong?

How many oxygen sensors on 1999 Toyota corolla?

I think only 1. it's located below exhaust manifold before the cat converter.

What is the TCM on a 1999 Kia Sephia and how does it affects oxygen sensors?

The TCM is the transmission control module and it has nothing to do with oxygen sensors!

1999 Toyota Sienna CE Tail Light Passenger Side?

If the tail light on the passenger side of a 1999 Toyota Sienna CE is out, it is most likely a blown bulb. The bulbs can be purchased at any auto parts store.

Where is the vehicle transmission speed sensor located on a 1999 Toyota Sienna Van?

i have a 1999 Toyota seinna v6 and i will know where can i find the vehicle speed sensor.

How many quarts of fluiD dOes a 1999 toyota sienna automatic transmition hold?


How many o2 sensors does a 1999 ford ranger xlt have?

That Vehicle has 2 oxygen sensors.

How many oxygen sensors on 1999 Mercury Sable?


Where are the oxygen sensors located on a 1999 camaro?

Exhaust system.

How many oxygen sensors are in a 1999 Porsche boxster?


How many oxygen sensors are there on a 1999 Mercury Villager?

There are two.

How many oxygen sensors in a gmc Yukon 1999?


How do you replace the rear door handle on a 1999 Toyota Sienna minivan?

check out this website it tells you how to repair the handle since it cost about $65.00 to buy a new one.

Where is the oxygen sensor in 1999 mercury villager?

The oxygen sensors are in the exhaust pipes on most models.

Where are the oxygen sensors located in a 1999 Dodge Intrepid?

There are four total oxygen sensors. One before and one after the catalytic converter on each side of the engine.

Where are the oxygen sensors on a 1999 Lincoln town car?

Go to type in oxygen sensor and it will allow you to pull up a diagram of all o2 sensors

1999 Toyota Sienna turn signals quit working?

Check fuse or turn signal flasher

Where is cylinder 5 on a 1999 Toyota Sienna?

On the cylinder bank nearest the firewall, the one that is closest to the transmission.

When replace timing belt Toyota Sienna 1999?

Replace it every 90,000 miles. Warning: This is an interference engine. If the belt breaks serious engine damage will occur.Not true, 1999 Sienna DOES NOT have an interference engine