Ok guys, one more time with a DTC PO136

[David Johnson]

Ok i went to autozone and had them read my code for my E150 4.2L with 91600 miles on it. It was PO136. A malfunction exists in the electrical circuit for oxygen sensor 2 in Bank 1 . Just wondering if you guys could help me with this. I have NO driveability issues with this code. Should i just reset the PCM or should i have this looked into further?

[King James]

Either means it is bad or disconnected. It is most likely bad unless someone decided to disconnect it for some unknown reason or something happened with the wiring going to it like it got cut or something. Could cause the mileage to go down or make the engine run other than normal. I'm not absolutely positive about the later though.

[SSCULLY]

Here is the full run down from the Manual on P0136 :

DTC
P0136 - HO2S Sensor Circuit Malfunction (HO2S-12)

Description
The downstream HO2S sensor(s) are continuously checked for maximum and minimum voltages. The test fails when the voltages fail to meet the calibrated limits.

Possible Causes
Pinched, shorted, and corroded wiring and pins.
Crossed sensor wires.
Exhaust leaks.
Contaminated or damaged sensor.

Diagnostic Aides
none

I only found 1 other post where a memeber had this error.
O2 Sensors Question

Seems his soultion was a replacement of the ( correct ) O2 sensor. While this may or may not be the same as yours, taking a look at HO2S-12 to see if the wiring is damaged, or if the pin connector is not crapped up might be a place to start.
All other searches on P0136 had no additional information.

Have they been replaced at all ? The only reason I ask is if they are the origional, maybe the pins are corroded in the 4 pin connecotr ( truck harness to O2 hharness ) and it might be a case of corrocsion causing a high resistance connection, causing a voltage drop, which causes the code. ?? Just a guess.

Good luck with this one, post back when you find the answer for the next guy.

[David Johnson]

SScully,
#1- Is O2 Sensor #2 in bank one the sensor on the passenger side behind the catalytic coonverter?

#2 Do these sensors just unscrew and ya screw another one in.? Does the sensor come with the plug that plugs into the harness? or connector?

#3 Is the truck harness to the O2 harness the big fat square one under the hood? There are 3 harnesses under or behind the air intake. Which one are you talking about?

#4 If the pin connector is crapped up how would you clean it?

#5 all sensors are original and have never been replaced

#6 Wiring, if i was looking at the correct sensor did not look bad.

This light has come on and gone off previously. It did go off on its own for a short period today. Then it came back on

Thanks
Dave

[SSCULLY]

David,

HO2S-12 should be drivers side behind the cat ( the easier ones to get to ). #1 is the drivers side, #2 is the pass side ( hope my memory is not failing me right now on something so simple ).

I forget the wrench size, but it is screwed into a bung in the pipe. The harness should be a 4 pin square connector ( at least it is on my 01 ).

The O2 sensor will come with the pigtail and the connector on it, as long as the guy at the parts place gives you the correct one, it is a bolt in and plug in and go type of thing.

The harness that I refered to with maybe being corroded would be the one down by the O2 sensor itself. The pigtail I think is about 12 or 14" long.

If the O2 sensors have never been changed in 91K miles, it might be a good idea to do them all. But if you don't really want to play with them, trying some electrical contact cleaner might be a a good idea. O2 sensors are kind of normal maintenance items now, requiring changing before failure. ( at least that is the concensus around the forum these days ).

If the wiring itself seems good, then 1 of the possiable problems might be a corroded connector. This adds high resistance to the circuit, and will cause a voltage drop. The other possiable problem is the O2 sensor itself is out to lunch. That is what the other member posted being the cure for his same DTC code.

If you take a look at ordering one online or from a parts place, they are about 40 to 60 for a Bosch O2 sensor. Considering it is the easy one to get to, you might want to try changing that one out, and reset the PCM to see if it is the cure.

Like I said one other member this was his cure for the same DTC, but there are other options that is can be. Maybe taking apart the connector can cleaning it first is a good place to start. Clean both the male and female sides of the connector, and put them back together, see what happens.

The changing of all them is up to you, but concensus is this is a normal maintenance item that gets changed around 60K miles or so.

Good luck, post back what cures it for you.