CEL code

[97exploerjunk]

Hi all new to form and have been trying to fix my 1997 ford explorer for months now i keep getting the CEL and code p0136 and comes up P0136 Ford - O2 Sensor Circuit Malfunction Bank 1 Sensor 2 now sensor 2 is the one after the cat? if so i have replaced it twice the first time the truck was running really bad and the plug for the sensor was melted got a pigtail and replaced it with a new o2 sensor rest the light and it keeps coming back same code i checked the wires as far as i could and found no breaks or shorts as far as i can tell the truck needs to pass inspection (have a 10 day) need help anything to point me in the direction would be great thanks

Sam

 

[ZWilson07]

Did you change the drivers or passengers side rear O2 sensor?

Do you have any diagnostic tools or at least a volt meter?

 

[97exploerjunk]

I replaced all 3 of the o2 sensors bank 1 sensor 1 and bank 2 sensor 1 and bank 1 sensor 2 i have only 3 sensors and i have an obd2 reader and a volt meter

 

[ZWilson07]

I replaced all 3 of the o2 sensors bank 1 sensor 1 and bank 2 sensor 1 and bank 1 sensor 2 i have only 3 sensors and i have an obd2 reader and a volt meter

Ah 4.0 OHV, thats right. Didn't know if you had the v8 or 4.0 SOHC.

Whats your O2 readings on that sensor?

Do they fluctuate or stay constant?

 

[97exploerjunk]

i think they stay constant but will check again to make sure

 

[ZWilson07]

i think they stay constant but will check again to make sure

Your front 2 should be constantly jumping back and forth from rich to lean with your rear O2 staying more constant to show health of the cat.

Getting a reading of the rear one will help narrow down if it is in fact having a malfunction or if it is giving normal readings. Also make sure the system is warmed up and in closed loop when looking at the reading.


Might also be worth clearing the code while monitoring it and seeing if it throws the code again immediately or if it gives a normal reading, and only throws the malfunction code at a certain time/load/etc.



If it functions normal, try and swap O2 sensors to see if the code follows the sensor or stays. Will help narrow down if it is an actual bad O2 sensor, or if its an open or short in in the signal wire itself, or possibly even a small exhaust leak.

 

[97exploerjunk]

sensor was replaced and the exhaust front to back is new converter and all

 

[97exploerjunk]

is there a wire diagram for the wires for the after cat o2?maybe they wired the pigtail worn

 

[Turdle]

Another thread with the same issue. Just in case a resolution is found


http://www.explorerforum.com/forums/showthread.php?t=423243

 

[97exploerjunk]

Hey All update shop went through the wires and found some more melted cut away and replaced with new wire from the pigtail, light still came on and the same code po136 so bought a new ecm replaced it and still the same code does this mean i will have to have the whole wiring harness taken apart and looked through? (just for the o2) and the other 2 o2's are working as they should the voltage go's up and down and the o2 after the cat in a closed loop has 0 volts thanks again for the all the help so far