Check Engine Light Due to Failed Oxygen Sensor on Toyota Sienna

Problem Description and Possible Solution

One or more oxygen sensors may fail resulting in illumination of the Check Engine Light.

Problem Data
RepairPal Verified
Average mileage: 111,629 (13,000–220,000)
12 model years affected: 1998, 1999, 2000, 2001, more2002, 2003, 2004, 2005, 2006, 2007, 2008, 2011
99 people reported this problem
Viewing 1 - 20 of 40 comments
The van functionally is great. It does not affect the way it drives at all. The check engine light came on and Auto Zone ran a diagnostic test; this test indicated that one of my O2 sensors was bad.
The engine light comes on along with vsc light.
engine light came on we plug a hand held diagnostic tool it read H025 Bank 1 sensor 2 heather circuit low.I need to see where bank 1 and 2 are located.
oxigen sensors may fail resulting in ilumination of check engine light
Very upset. Oxygen and fuel sensors bad on Toyota Sienna that only has 13,000 miles on it and has been impeccably maintained. Not a Toyota fan if I am going to have to pay for this.
Not sure about mileage.

Had to have 2 sensors replaced within a couple of years. Mechanic suggested clicking gas cap at least 7 times when tightening. Have had no problems since...fingers crossed.
Had to replace both oxygen sensors in past four years.
Initial problem was indicated by "Check Engine" light. Follow-up with a OBD-II code reader (a $40 must-have item for a DIY repairman) pin-pointed a faulty Air/Fuel sensor on rear exhaust manifold. Replaced with a new sensor (about $160) from local parts store. Access to the sensor is cramped and limited, but certainly do-able. Cleared codes, replaced sensor, drove for 100 miles, passed state emissions inspection, no issues after 2 months.
Check engine light came on at about 25000 miles. Toyota dealership found thatboth O2 sensors were bad . I had them replace them at about $600. At 50,000 miles the O2 sensors went bad again. This time I did not bother replacing them as the gas mileage not noticeably affected. But, I need to stare at the check engine light every day.
Bought as CPO vehicle and 6 months later check engine came on. Dealer said was bad oxygen sensor and $500 fix, fortunately covered under warranty. Waited 3 weeks to get part and then appointment. During that time noticed in addition to check engine light, lost stability control and had much lower fuel economy until it was replaced.
Replace downstream front bank (left side) oxygen sensor - to turn off check engine light and pass inspection.
not fixed yet, check engine light due to oxygen sensors problem. 226$ for the parts, not sure it worth it.
I had the Toyota dealership/repair here check because of the Check Engine light on dash; I'd had an auto parts store test the problem first.
I told them I'd read all of your good info, and that someone had posted that a new part would cost about $160, plus labor.

Today, the young man came back to the service waiting area and told me that because the engine/van was made in California? the sensor would cost $260, plus now I can't remember, $400 for labor? Or $200, I think. I was appalled.

I asked why so expensive, I saw it on Youtube and it didn't seem to be a big job. He said the parts are rusted, whatever that means---I assume the parts that have to be hooked up to the sensor or ?

Why do I need a sensor that is for a specific state, when NC doesn't required such strict emissions testing, I am sure. I told him that but I don't have a clear understanding of it...I'm old, and haven't had to deal with the cars in the family before.
We've only had this van for about 3 years, bought with 200K miles on it, our daughter insisted we get something we could get in and out of easily. It has been a boon in that regard, but I've been concerned because it's old and has so many miles. (I actually love the van, it has (well worn) leather seats, and wish we had a new one like it and that we'd always had a van!) We had the 3rd row and one seat from the 2nd row taken out and stored in the garage; very handy to just put our groceries into the side and when moving house.

I paid for today's service, and they'll order the part (from California, he said). Does having to buy the specific sensor for California sound logical to you? I liked the entire setup there, and the service man was very patient with old me, and I understand things don't come for free.

Then, of course, to confuse the issue, the Check Engine light didn't appear after I'd driven away, stopped somewhere, and started up again...I am sure it was still there when I left the dealership.

Thanks very much for your site, it's very informative.
O2 sensor has failed
O2 SENSOR FAILURE
Failed oxygen sensor
This is a known problem - pretty much all of the O2 sensors will crap out at about 100,000 miles. the 2001 Sienna has 3 sensors - two (the frontunder hood easy access and the rear under the vehicle easy access) can be taken care of by the home mechanic. Order OEM sensors off of ebay. the third )2 sensor is a total bitch to get to - I hired a guy off of Cragistlist - took him about an hour to get the old one off and plug in the new one) - there are some good DIY resources on line for this. Also my knock sensors went out in the engine at around 100K - did the same think - senors off of ebay and a relable mechanic to install.
I was driving one day and my check engine light came on. I took it to Advance Auto Parts and had a Diagnostics ran on it and they said my O2 sensors were messed up.
Not fixed yet, as I'm tight on money. Check engine, bad, and Trac off lights are now on in my van. Dealer says it's all because of bank 1 sensor 2 needs replacing.
Check engine light going on and off, finally had it diagnosed and it has an O2 sensor that is not working at all.