Sienna air fuel sensor

Toyota calls a wide band oxygen sensor an air-fuel sensor. Because of the low production volume, I think Denso is the only source, unfortunately.

A quick reverse lookup suggests yours is a 2001 Sienna?? If so the following upstream sensor costs $136.79+shipping on rockauto.com.

I appreciate the information. Yes, I believe the sensor this is bad is the middle one of the three. Located at the bottom of the manifold before the converter. Perhaps I used the wrong term when I said air/fuel sensor. But even the rockauto site you directed me to states it as a air/fuel ratio sensor. But it shows the price as 151.79. You mention a part for 84.79--did you have a part number?

Again, thank you. You at least saved me 50 dollars.

Rob

snipped-for-privacy@hotmail.com wrote:

Sounds like you're referring to the Right Bank wide band sensor then. Before the catalyst. So it's not the $85 one. *Always verify* using manufacturer's catalog (even then there are errors). For a Denso sensor this is:

V6 / 3.0L ID: 1MZFE 234-9021

($136.79+shipping, rockauto.com)

Sometimes a Denso reboxed by Bosch is cheaper, but in this case the

I'm trying to figure out if it is the one after the converter. Some reading I've done suggests that the bank2 sensor refers to the heated o2 sensor after the converter. I'm beginning to think this code P0136 is telling me that my heated o2 sensor after the converter is bad. In which case it would be the cheaper $85 one.

All sienna's post 2001 have a/f sensors upstream (sensor 1). I think there is one on each bank (a bank refers to 3 cyl). The sienna as a v6 with two banks. Bank 1 refers to the bank with cyl 1 (near the fire wall) in it and bank 2 refers to the opposite side of the engine (near the radiator). I've read that all sensor 1's are before the converter in the manifold and all sensor 2's are after the converter or downstream.

So with my vehicle which has three sensors, I believe they are called out like this:

1. bank1 sensor 1 (a/f sensor fire wall side of manifold)
2. bank2 sensor 1 (a/f sensor radiator side of manifold)
3. bank 1 sensor 2 (heater o2 sensor after converter.

Sound reasonable?

Take care, Rob

snipped-for-privacy@hotmail.com wrote:

Yeah, the two upstream sensors should be identical and in the order you described. The P0136 code points to the *downstream* sensor. (that's why OBD codes really help)

Besides the problem with the sensor itself, there is a chance that the problem is with the wiring or even less so with the ECU. One owner (of a Camry IIRC) had the problem with an ECU, and a mechanic tried to bypass a transistor that turns on the sensor without success.

That said, oxygen sensors (by whatever name) are wear items (minute amounts of sulfur and other contaminants in engine oil and gas) and I'd replace after ~100K miles.

So yeah, the P0136 suggests it's the downstream $85 one. The proper way is to diagnose and rule out other faults (wiring by checking connectivity and ECU by substituting a known good one). Now these are easy at a shop, but much more difficult for the owner. If over 100K miles, chances are, the upstream ones are probably not far behind.