2001 Sienna CEL code P0141 keeps coming back

[safedriver]

Hello forum members,

I got a CEL code P0141 (oxygen sensor , bank 1 sensor 2 on firewall side) on a Toyota Sienna 2001. Changed the oxygen sensor, reset codes, drove around, got the code P0141 again. Changed the sensor to another new one, got the code P0141 after few miles driving around. Changed to a third sensor, drove about 20 miles and got P0141 again. Why does this keep coming back? All the sensors can't be malfunctioning.... First replacement sensor was a Bosch, the next two were Denso..... I'm confused as to the problem.....

anyone with similar problem and some kind of solution?

[chuck's sienna]

Welcome to the club! I gave up, took the speedo panel out and removed the check engine light bulb. This code does not effect driveability so I just live with it. This code is a tough one to beat.

[wiswind]

P0141 is for Bank 1 Sensor 2 HEATER circuit malfunction.
This is the sensor that is located in the exhaust pipe AFTER the catalytic converter.
You have 3 oxygen sensors, 2 Air/Fuel sensors, which are wide band oxygen sensors that are used to control the engine (like how much fuel to spray in).
The other sensor monitors the function of the catalytic converter.
The P0141 is indicating a problem with the oxygen sensor that monitors the catalytic converter.
It is located under the car......kind of under the passenger seat.
The wires go from the sensor, up through the floor of the vehicle and plug in under the front left corner of the passenger seat.

The heater should measure between 11 and 16 ohms at around room temperature.
This is as measured between the B+ (Pin 1) and HT Pin 2) pins on the connector.
The diagram for my 2003 indicate that
B+ (Pin 1) will have a BLACK with RED stripe wire.
HT (Pin 2) will have a BLUE with White stripe wire.

You DO NOT need to remove the whole seat to get to this connector.....just the plastic trim panel that goes along the bottom of the seat mount on the driver's side.
You unplug the sensor, and push the grommet and wires down through the floor, then access from below.

It looks like the top left wire to the connector is Pin 1 Light Blue with White stripe. and the top right wire will be Pin 2 Black with red stripe wire.

Here is a picture of the connectors on my 2003 sienna......under the passenger seat......front left corner


This is a picture of bank 1 sensor 2
Hopefully those nuts are not too rusted onto the exhaust pipe.






As you have changed the sensor.......hopefully, the heater is OK.
However, looking at the wiring diagram for my 2003 Sienna, the B+ goes to the ignition ON.....and should have power whenever the ignition switch is on (you could check this at the sensor connector) and the HT lead goes directly to the ECM (computer) pin 9 of connector "B".
Power comes into the sensor heater through the "B+" at pin 1 and the computer provides the ground path for the heater.

[chuck's sienna]

Great pictures. Safedriver start with the O2 sensor shown in the second picture, the one after the cat. Then go from there.

[Black Sunshine]

Caution ambiguity. There are only 3 sensors. The two front sensors (also referenced as pre-cat) are technically air/fuel sensors but they are still commonly referenced as oxygen sensors. This is because they are a newer style. The rear one (also referenced as after-cat) is a more normal oxygen sensor. Two front, one rear.

I've replaced two of mine in my 230,000 miles. They were both in the front. In both cases I replaced the sensor that was indicated and erased the code. After that the problem went away.

[TOYOPARTSMAN]

I know there are all kinds of aftermarket sources for these sensors, but I have heard some members having problems with them, even down the road later. If you are interested in Genuined OEM sensors, I sell GENUINE OEM Toyota parts to members for a 30% discount off MSRP.

Good luck to you all.

[BigSmile]

Have been told using racing fuel will kill them. Lead in the fuel.
Check motor mounts. Sagging can pinch and short one of the sensor wires. Get the Denso brand sensors. They will last and have a decent price tag.