p0136

[Black2000Ranger]

Good morning TRS.
After I changed my engine I kept getting 3 codes. Now it seems as though I only have one. The light will be out for a tank full, then I fill up and I get this code. It seems to like to come on once I hit a pothole. My book says malfunctioning circuit. Anyone ever have this code before and find out it was something other than a o2 sensor?
Thanks!

 

[ATXTremor]

I know the original post is quite old, but I just wanted to share my recent experience with the P0136 on my 2000 Ford Ranger XLT 3.0 V6 (Flex Fuel). It might help someone who is scratching their head about it. My engine had a rough idle and poor acceleration when pressing the gas at around 40mph. It originally did not give me a code. I did all of the following to try and resolve the issue:
Cleaned air filter, cleaned MAF Sensor, removed throttle body and cleaned, removed and cleaned IAC, replaced IAC gasket, ran some over the counter fuel injector and gas treatment, replaced spark plugs, replaced spark plug wires, replaced EGR valve and gasket.
All that seemed to help a little bit, but it was still sluggish and the engine was vibrating way too much. I had replaced the engine and transmission mounts a few months prior so I didn't factor those into the rough idle equation.
One day I went to fill up on gas. Instead of filling her up with the medium grade gasoline that I usually do, I instead used the regular stuff. On the way home, the acceleration issue got way worse. Now I had difficulty accelerating at 20mph and I could feel the pedal and engine shake when trying to accelerate. But this time, it finally gave me a code, P0136.
I know this code calls out the O2 sensor behind the Cat, but I went ahead a replaced all 3 O2 sensors. I also sprayed some Seafoam Cat cleaner down the lines because I thought maybe a clogged Cat might be the culprit. I also decided to go ahead and replace the fuel filter as well. I filled her up with some better gas, and that did make the P0136 code go away, but the rough idle and poor acceleration remained.
Simply on a hunch, I decided to go ahead and replace the fuel injectors. My truck is 24 yrs old and has 140K miles on her and they've never been changed. Well, when I took out the old injectors, I measured the resistance on them and discovered I had 2 faulty ones (one on each side). With the new injectors, the engine no longer shakes and she accelerates smoothly. The P0136 error can be caused by the ECU detecting a lean mixture. When you have a faulty injector (or two), this can cause the fuel/air ratio to be off.
Anyways, I hope this might help someone who is receiving this P0136 error.

 

[Jazzer]

Good info, thanks.