I have a code po135,on my 4 cylinder motor. using my actron scanner cp9150 i find two 02 items which are labeled 02S12V & 02S11V i assume that the 12 means behind the cat. and 11 means before the cat,

so, engine is warm, the 02S12V volt reads .001 to .09 up and down. But the 02S11V reads 3.298 with no change. this leads me to beleave the (before the cat) sencor 02S11 is the problem but if so why would it read 3.298 Volt? i would think if its bad it would read 0.0volt

 

OK, I see you've started this thread, so i'll cut & paste my answer to this question thats on the other thread.

OK, so lets think about this some more & see if we can unravel what you've posted.

The OBD-2 trouble code you posted P0135 = Bank one/passenger side cyl bank, on rear wheel drive vehicles, sensor one/before cat O2 sensor heater circuit malfunction. This means that without the heater, the O2 sensor will be slow heating up & coming online/going into closed loop operation.

So you need to test, to determine if its getting B+ voltage to the O2 sensor electrical connector at KOER. If so, then with the O2 sensor electrical connector disconnected, test across the O2 sensor heater connections, to see if the heater is open circuit. If it is, replace it & I'd also replace the upstream O2 sensor in the other cyl bank, so the computer will get a balanced O2 input from each cyl bank.

I'm not clear on what you've posted about which O2 sensor read what. It sorta seems you might have the readings reversed, or not correctly interpreting your scantool display. The switching voltage number posted, would be a normal range for the before cat/sensor 1 to read.

The after cat/sensor 2 voltage reading should remain fairly steady, but not around 3 volts, so I'm not sure whats going on there, as it indicates a really Rich fuel level, or that the cat converter isn't working????!!!

Do you have any other set, or pending trouble codes?????

Look in your CP9150 Manual Supplement "PIDS For Scan Tools", on page 20, for how to de-code your CP9145 scantools O2 sensor nomenclature/display.
Basically O2S11 = Cyl Bank one/passenger side, O2 sensor one/upstream before cat O2 sensor.
O2S12 = Cyl Bank one/passenger side, O2 sensor two/down stream after cat O2 sensor.

O2S21 would = Cyl Bank two/drivers side, O2 sensor one/upstream before cat O2 sensor.
O2S22 would = Cyl Bank two/drivers side, O2 sensor two/down stream after cat O2 sensor.

 

thanks for the reply, ill try to clairify. on my scan tool there are two items, (among others) that referre to the oxygen sensor, "02" telling me of the voltage condition. The first in the list is labeled as 02S12V which i beleave is the sensor after the cat, and its voltage reading goes up and down between about .1 to .9 which i think is normal. But the other 02S11V which i beleave is telling me about the sencor before the cat? The sensor before the cat., 02S11V has a volt reading of 3.298 fixed. Its a 4 cylinder so there is no left right bank. I would be quick to just replace the sensor before the cat as a prosess of elimination but autozone and pepboy price is $195 for the sensor, ouch. Most sensor are around $40-$60 but not this one. I need to be sure if i have bad sensor or other issues.

 

EDIT: OK its a 4banger, so yes you won't have a bank 2 O2 sensor.

So your positive about the scatool O2 sensor readings. If so, the before cat O2 sensor is reading Way high indicating Rich/No O2 in the exhaust, or maybe you have a short between the up stream O2 sensor heater & O2 sensor signal wire. In any case the before cat O2 sensor has a trouble code for its heater circuit, so begin checking that out, check the wiring for broken wires, or skinned insulation & the wire strands shorting out to ground, or each other.

The before cat O2 sensor should be switching like you say the After cat O2 sensor is doing & the after cat should be reading a slowly switching or nearly no changing voltage if the cat is properly working & the computer is properly controling the air/fuel ratio.

I suppose you could have an acting out badly leaking fuel injector, causing a really rich fuel mixture & if so, seems to me you'd likely have other trouble codes & other engine run symptoms, like a really smelly exhaust, the cat converter over heating & glowng cherry red, fuel mileage really bad, poor idle quality, ect.

 

I double checked the scanner and yes the 02S11 is reading 3.298 volts, the wires look all good so my only conculusion is there must be an internal short in the 02 sensor, next ill unplug the sensor im told between the heater and ground i should get 4.5 ohms and i assume then between the heater + and either hi or low i should have open but if i get anything between heater + and hi or low then i will assume that there is a short ?? what do you think, am i thinking right? thanks

 

That sounds like a plan. Also with the O2 disconnected, probe/check the O2 electrical connector pins/sockets to make sure theres no short in the wiring harness to the sensor & that the sensor heater is getting voltage at KOEO.

If you come believe its a faulty sensor, here is a link to some good Advance Autoparts discount codes, that can save some serious $$$$$!!!!
Advance Auto Parts Coupons & Promo Codes 2012, Advance Auto Parts Online Discount Codes I've recently used the 40% off codes for a battery, ignition cables, oil filters, ect. Order on line with the code, pick up in store with no shipping!!!!! Merry Xmas!!!! lol

 

BUMP:

Well donaldm, hows it going, curious minds would like to know????

 

i pulled the 02 sensor out. wires look very good. its a 4 wire sensor . . . two black, one white, one blue. the ohm reading between any combination is 0 (open) I assume the two black are heater, if so there should be 4.5 ohms. but with an open reading between all combinations i dont know why i would get the 3 volt from the scanner unless there is a minute short that only happens when voltage is applied. in any case I have to assume the sensor is bad. I shopped it around and found a price down to $108 my next job is to verify a part number which is different between different supplers. thanks

 

What year are we working on?

 

Advance Auto has the upstream O2 sensor for $44 & with the above 12/21 promo code link I've posted, you'd find codes for at least another 20%-40% off that figure, when ordered online & picked up in store with no shipping charges. So you can do a lot better than $104 for an upstream O2 sensor for your 2000 4banger.

 

ok thanks ill check it out.