P0136 Code and O2 Sensor 2 Bank 1 voltage

[AeroRamer]

P0136 Code and O2 Sensor 2 Bank 1 voltage (with Chart)

Advice is what you ask for when you know the answer but wish you didn't. So...I ask....

I got a Code PO136 today on my 2000 Explorer V6 SOHC, 180K, which my Actron CP9580 points out to be the Oxygen Sensor 2 Bank 1 (O2S12)[code corrected] . I cleared the code and will be monitoring for recurrence as I continue driving the Ex. From what I've read here it could be several things like the O2 itself, wiring, the catalytic, or dirty connections.

I ran a stationary Driving Monitor Test and looked at the O2 sensor voltage readings for 25 frames (64 seconds) while changing gears from Parking to Drive and back to Parking. The voltage rading were as follows:


Bank 1:
Sensor 1 (O2S11): .040 - .760
Sensor 2 (O2S12): .000 - .210 ---> Suspect per OBD2 Scanner(?)

Bank 2:
Sensor 1 (O2S21): .040 - .740
Sensor 2 (O2S22): 1.275 - 1.275

[codes corrected]

Since there is a lot of talk that sensors are seldom the culprit I am curious as to what is the normal voltage range is for these oxygen sensors. Can you tell by the readouts if a sensor is faulty?

Sometime this weekend if I get the chance I will get under the hood and inspect the wiring and do a little spring cleaning before I start replacing parts or doing a more detailed troubleshooting and checking for leaks, or start sweating about the notion of thinking of the catalytic.

Few notes about the Ex:

The Idle on the Ex is not as smooth as I think it could be but it is not bothersome or problematic. I am sure I have a very small coolant leak somewhere that I have not been able to find. I know because at one point the Ex was making a lot of 'hamster' noise in the console area (heater core/lines(?)) and was overheating. After I replaced the thermostat I realized that there was a good amount of coolant missing in the radiator. The reservoir was full.

Any ideas?

.

 

[2000StreetRod]

bank then sensor?

P0136 02 Sensor Circuit Malfunction (Bank I Sensor 2)

I seem to remember that the first digit is bank and the second digit is sensor. For example O2S11 is bank 1 sensor 1 and O2S22 is bank 2 sensor 2. Anyway, I believe the voltage of 1.275 is erroneous. The range of 0.0 to 0.2 is also suspect. The range of an O2 sensor degrades with age, new: 0.95 to 0.07 volts, aged: 0.83 to 0.09 volts

 

[AeroRamer]

P0136 02 Sensor Circuit Malfunction (Bank I Sensor 2)

I seem to remember that the first digit is bank and the second digit is sensor. For example O2S11 is bank 1 sensor 1 and O2S22 is bank 2 sensor 2. Anyway, I believe the voltage of 1.275 is erroneous. The range of 0.0 to 0.2 is also suspect. The range of an O2 sensor degrades with age, new: 0.95 to 0.07 volts, aged: 0.83 to 0.09 volts

Hmmm, interesting. I used the website 'Live Data Abrreviations' to find which one was B1-S2. There it said that it is O2S21. After you mentioned that it was the other way around I found the website ATA Pro's Place that agrees with your statement. If we use the this format then the arrangement becomes:

Bank 1:
Sensor 1 (O2S11): .040 - .760
Sensor 2 (O2S12): .000 - .210 ---> Suspect per OBD2 Scanner(?)

Bank 2:
Sensor 1 (O2S21): .040 - .740
Sensor 2 (O2S22): 1.275 - 1.275

Does this make better sense now?

 

[2000StreetRod]

OBD criteria

According to the 2000 Model Year OBD System Operation Summary:

Rear HO2S Signal
A functional test of the rear HO2S sensors is done during normal vehicle operation. The peak rich and lean voltages are continuously monitored. Voltages that exceed the calibratable rich and lean thresholds indicate a functional sensor. If the voltages have not exceeded the thresholds after a long period of vehicle operation, the air/fuel ratio may be forced rich or lean in an attempt to get the rear sensor to switch. This situation normally occurs only with a green catalyst (< 500 miles). If the sensor does not exceed the rich and lean peak thresholds, a malfunction is indicated.

P0136 No activity, Bank 1
Typical Rear HO2S check malfunction thresholds:
Does not exceed rich and lean threshold envelope:
Rich < 0.25 to 0.50 volts
Lean > 0.40 to 0.65 volts

 

[bobflood]

If you get a clear code that says there is an O2 sensor problem, it is likely that the sensor is indeed a problem. I have usually had excellent results from following the guidance of the scanner information.

I second streetrod's opinion on the code - the first number should be the bank and the second the sensor.

 

[2000StreetRod]

O2 sensor wiring

Here's the O2 sensor wiring for my 2000 Sport. It may help you sort things out.

HO2S #11 (Bank 1 Pre-cat)
Gray/Light Blue (O2 voltage to PCM)
Orange (sensor return common)
Red/White (Heater output to PCM)
Light Blue/Orange (heater supply)

HO2S #21 (Bank 2 Pre-cat)
Red/Black (O2 voltage to PCM)
Orange (sensor return common)
Yellow/Light Blue (Heater output to PCM)
Light Blue/Orange (heater supply)

HO2S #12 (Bank 1 Post-cat)
Red/Light Green (O2 voltage to PCM)
Orange (sensor return common)
White/Black (Heater output to PCM)
Light Blue/Orange (heater supply)

HO2S #22 (Bank 2 Post-cat)
Purple/Light Green (O2 voltage to PCM)
Orange (sensor return common)
Tan/Yellow (Heater output to PCM)
Light Blue/Orange (heater supply)

 

[AeroRamer]

Update. After I cleared the code it took about 10 days for the Check Engine Light to come on again. Then, after a couple of days the light goes off again. It has been doing that for the last month and a half. :scratch:

 

[Liska]

Update. After I cleared the code it took about 10 days for the Check Engine Light to come on again. Then, after a couple of days the light goes off again. It has been doing that for the last month and a half. :scratch:

Is your gas mileage affected?

 

[bobflood]

Update. After I cleared the code it took about 10 days for the Check Engine Light to come on again. Then, after a couple of days the light goes off again. It has been doing that for the last month and a half. :scratch:

Not uncommon for O2 sensors when the sensor reading is the issue; they get progressively worse so for a while they just throw the codes occasionally, then the problem clears and the computer turns the light off again. Over time, the good interval will shorten and eventually the light will stay on. When the O2 heater fails (the other problem with O2 sensors that throws a different code), that's usually it - the light will not go out.

 

[AeroRamer]

Is your gas mileage affected?

No, not really. If there has been a decline it may be less than half a mile per gallon but that may be my latest driving habits, which I changed lately to test some motorcycle turning technique. I usually average 22.2 mpg. Lately, I've been getting ~21.5 to 21.8.

Not uncommon for O2 sensors when the sensor reading is the issue; they get progressively worse so for a while they just throw the codes occasionally, then the problem clears and the computer turns the light off again. Over time, the good interval will shorten and eventually the light will stay on. When the O2 heater fails (the other problem with O2 sensors that throws a different code), that's usually it - the light will not go out.

I hope that the problem is with a bad O2 sensor. I am somewhat like others here that think that O2 sensors don't usually go bad and they are working as designed sensing a problem. I guess I'll schedule a day for it and replace the O2 sensor. Should I do both the forward and aft or just replace the 'suspected' bad one?

 

[ucluglee]

Let me add something, only because I was getting identical and similar codes: when was the last time the fuel filter was changed? The reason I ask is about 6 months ago I started getting the same codes and bank 1&2 lean codes. I started with the least expensive resolution I was given and changed the fuel filter. No more codes since the filter was changed. Just wanted to throw out that suggestion.

 

[da fiddler]

Where is bank 1 sensor 1

Hi folks can you help?

I've run a diagnostic on my explorer, and have to replace the o2 sensor that is at bank 1 sensor 1 - my question is how do i work out which is which?

RHD UK 4.0 stock explorer

Thank you for any help

 

[2000StreetRod]

passenger side, precat

In the U.S. bank 1, sensor 1 is the one on the passenger side downpipe before the catalytic converter. I don't know if the numbering is the same in the U.K. If you have a OBD code reader you can disconnect that one and see if you get an O2 heater fault for bank 1, sensor 1.

 

[bobflood]

Hi folks can you help?

I've run a diagnostic on my explorer, and have to replace the o2 sensor that is at bank 1 sensor 1 - my question is how do i work out which is which?

RHD UK 4.0 stock explorer

Thank you for any help

I understand that bank one is always the bank with cylinder #1. In US, that is the bank on the right side (AKA passanger side) of the engine. Sensor #1 is the one before the catalytic converter.

 

[AeroRamer]

Go figure. I have not seen the light come on for a few weeks now that I totally forgot about it. I am sure the light will come on now that I have mentioned it. Oh, well...light's off, move on. At least for now.

 

[lobo411]

My 1996 Explorer is not throwing a code, but I noticed that the Sensor 2 Bank 1 O2 sensor is not sending any data (it reads 0.000V). I've been having a problem with rough idle on the second start (ie...start the car, drive it somewhere, park, come back in 20 mins, restart w/ very rough idle, shudders, etc...), so I looked at the live data and noticed it.

Is it possible to have a O2 bad sensor w/o generating a code?

 

[deadernie]

Just had this same problem on my Ranger. Bought a new rear O2 sensor and when I was taking the old one off one of the wires had been chewed by some sort of critter. Repaired the wire and reinstalled. Good to go!

 

[AeroRamer]

Update: I am now getting P0136 on an ongoing basis. I sense the Ex running a little bit more rough at idle than usual. Mileage is still around 21.5 MPG from about 22.2 about 2 years ago. I guess after 1.5 years it is time to get to it and replace the O2 sensor and see if it gets any better. Now, where was that video to replace the O2 Bank 1, Sensor 2? If I recall it was not something I was looking to do due to the difficulty getting to it.

Maybe unrelated but I am now getting P0442 (Evap Small Leak). I had the fuel pump replaced about a month ago so I will have the mech check for any loose lines, or cracked fuel neck. I do not think that will cause the little rough idle I am noticing.

 

[AeroRamer]

Update: I ran my OBD2 in recording mode while driving the car on the interstate. Below is the link to the charts of the tabulated data.

- Chart: Oxygen Sensors voltage (PDF Google Document)

The fuel filter was replaced a few months ago. I also replaced the spark plugs and wires. That did change the readings.

For O2 Bank 1/Sensor 2 (O2S12), if low voltage is suspect, does that mean I should replace it?

For O2 Bank 1/Sensor 1 (O2S11), and Bank 2/Sensor 1 (O2S21), if values for an aged O2 sensor is 0.83 to 0.09, should I replace them too?

The O2 Bank 2/Sensor 2 (O2S22) still shows a steady/static 1.275 volts. I cannot understand that one. Open?!

 

[AeroRamer]

Adding charts as pictures in case there is an issue with the PDF file on Google Docs.


Bank 1: Sensor 1 (02S11) and Sensor 2 (O2S12)

Bank 2: Sensor 1 (02S21) and Sensor 2 (O2S22)

All four Oxygen Sensors:

.