[ravid]

Hi all, I must say this site is great.:thumbsup:
I have 2002 corolla, its with me more then 2 years.
a year before i received check engine light, I took the car to my mechanic.
He printed the error message:
p0141 O2 sensor
heater circuit
malfunction (
bank 1 sensor 2
)

so he started to find the cause... he tested the ohm of the o2 sensor.
he tested the emission form the car, said the values are exact like how its should be.
so he suggested not to do anything, saying its will be a waste of money to change good parts.

the car still works good. been like a year later!
I saw there is some TSB about the problem but I didnt find the full detail of them. I founded 03-04 one that change the threshold of the car ECU from the sensors.
can you find the TSB?
What can be the problem?

yours ravid.

 

[ravid]

Well its been some time and still the same problem...
can anyone point me how to fix this?

 

[PiercedTiger]

I had to replace my cat a couple times. Car is burning oil. and that burns out the cat so the O2 sensor doesn't get the proper readings. After putting on the 3rd cat I said F this and bought an O2 sim. Haven't have a problem since I did that.

 

[fishexpo101]

Well its been some time and still the same problem...
can anyone point me how to fix this?

The issue is an electrical one in the sensor. The O2 sensor itself it probably still working, given your emissions levels are still fine. The part that failed, is the heater circuit. That heater brings the O2 sensor up to operating temperatures - decreasing the time the "rise-time" for values to be kicked back to the ECM.

Since this is sensor #2 or the downstream sensor, the exhaust gases will heat the O2 sensor for operation - that's why the emissions are still OK. But if starting from a cold start, there will be some confusion in the ECM, since the downstream O2 sensor is not providing the expected signal, since it will take longer to warm up compared to a sensor with a working heater.

The downstream one primary function is to check on catalytic converter function - only the upstream one is used for air/fuel mixture control.

Chances are - the car will still be fine with the burned out heater on the downstream sensor. The problem is if there is a new problem and you ignore it because the CEL is constantly coming on. Recommendation is to replace the sensor, sure you can keep running on the one with a burned out heater, but it doesn't mean the sensor will stay good forever.

 

[ravid]

Good to hear
I tried to look for the connection under the car, it's looks good.
Can I find where the cable goes in the car so I cheak the lines?
My technicen used ohmmeter on the sensor and found normal value so the sensor heater is probbly OK, the cable maybe got loose?

 

[fishexpo101]

The wiring connector is against the center tunnel of the car, have to remove the passenger seat to be able to pull the carpet away to expose the wiring for a visual inspection. You can "backprobe" the connector to read values with a multimeter.

There are 4-wires running from the downstream O2 sensor. 2 of those are for sensor operation (evidently still good on yours - usually blue and white) and the other two are for heater operation (usually black). The heater is a heating element inside the O2 sensor body.

Have to be careful in testing the O2 sensor, you can read the voltages off the sensor, but generally not resistance. You "can" check the resistance in the heater side, just not on the sensor side. Applying a voltage to the sensor side will almost always fry the O2 sensor or cause it to read incorrectly.

Heater circuit should show some resistance, but not be too high. If it is shorted to ground or open - it will read zero or megohms / infinite ohms. Could be one of the lines is shorted to ground, the other is fine - need to diagnose with a multimeter. Remember, don't measure resistance of the sensor, just the heater. You may get away with an accidental contact, but I would not risk it. An ohmmeter applies a voltage to a circuit to measure resistance. Even at low voltages, it could cook the O2 sensor.

Same goes for "cleaning" the sensor - you cannot clean the O2 sensor with solvents or brush off carbon deposits. The sensor is designed to be self-cleaning (gets really hot), they are designed with a finite lifespan, so they will eventually fail.

 

[ravid]

Again 10x for helping :thumbsup:

I saw this thread:
http://www.toyotanation.com/forum/showthread.php?t=320076

where there is a picture-

I understood its the yellow cable right?
I entered my hand in this area, without ejecting the seat.
so I didn't fell the yellow cable how goes up in the picture, like I don't have this in my car, maybe I Just didnt fell it right cause the seat is still on.
I tried to remove the screw but its hard as hell!

there as been also this picture in the thread:

I didnt understood to where its point me, to the silver connector on the right or the yellow cable in the left corner.
I opened the plastic where the handbrake.

again thank you.

 

[Guest]

an earleir post mentioned an o2 sim. what is that?

 

[brooklyn99corolla]

The issue is an electrical one in the sensor. The O2 sensor itself it probably still working, given your emissions levels are still fine. The part that failed, is the heater circuit. That heater brings the O2 sensor up to operating temperatures - decreasing the time the "rise-time" for values to be kicked back to the ECM.

Since this is sensor #2 or the downstream sensor, the exhaust gases will heat the O2 sensor for operation - that's why the emissions are still OK. But if starting from a cold start, there will be some confusion in the ECM, since the downstream O2 sensor is not providing the expected signal, since it will take longer to warm up compared to a sensor with a working heater.

The downstream one primary function is to check on catalytic converter function - only the upstream one is used for air/fuel mixture control.

Chances are - the car will still be fine with the burned out heater on the downstream sensor. The problem is if there is a new problem and you ignore it because the CEL is constantly coming on. Recommendation is to replace the sensor, sure you can keep running on the one with a burned out heater, but it doesn't mean the sensor will stay good forever.

fish do you know where this sensor is located? and how would it be changed? thanks

 

[dgoodhue]

fish do you know where this sensor is located? and how would it be changed? thanks

It's behind the catatlytic converter. It's located about where the shifter is. The interior connector is PIA t replace properly, I bet a lot of mechanics cut and splice the sensor wiring in.

 

[BigTDogg (MA)]

It's behind the catatlytic converter. It's located about where the shifter is. The interior connector is PIA t replace properly, I bet a lot of mechanics cut and splice the sensor wiring in.

The plug is exactly where my dead link picture shows it. I went cheap on the O2, wish I didn't, getting a P0141 now. I'll rehost the pics on my server later.

Thanks Fish for the diagnostic procedure.

 

[ravid]

Thanks for bumping, still the same error.
new pictures will be great

buy anyway I think there is no junction under the seat in the 2002 models.
I see only one cable in the hole under the chair, unlike the picture where you see a T cross.

 

[BigTDogg (MA)]

Remove the seat and pull back the carpet from underneath the center console. Be gentle as you don't want to rip all the clips out.

OK, once you remove the seat, you'll find the wire going to the grommet in the transmission/exhaust tunnel. Follow the wire up into the console trim and gently pull down until you expose the connector, then you can disconnect it:

Follow the rest of the guide in my original post and it's pretty easy.