Hey guys and gals,


My names Andy. I have been a proud ford owner my entire 32 years on this planet, and I have read many topics on this amazing forum, and I finally decided to join so I may help and get helped lol.


I am working on a 2000 expedition 4x4 5.4L expedition with 207k on it that a friend of mine picked up, and he asked if I could get it ready for smog. I performed a full tune up, fuel filter, plugs, boots, springs, changed all the coils, and replaced both o2 sensors for good measure.


When I test drove it the other day I got a code 1132 indicating a bank 1 sensor 1 o2 sensor issue. I used my code scanner to pull the PIDS and the signal voltage on that sensor was 1.275, and it wasn't changing. I read that the computers max voltage that it will display is 1.275 so, I proceeded to put my volt meter on it and much to my surprise, there is battery voltage on the o2 sensor signal wire. I unplugged and cleaned all the wiring harness connectors and put di-electric grease on all the connections. Still no change. The only time I saw a change was when I reached behind the engine on the drivers side and shook the harness, and it would dip back and forth indicating a short somewhere in the harness. I haven't removed the entire harness yet, and I'M really dreading it. I have even gone so far as to run a new length of wire from the o2 sensor up to corresponding pin on the PCM for that specific sensor, and it actually changes voltage now, but it still will peg up to 1.275 a good portion on the time when Im driving it, and now Im getting code 1131.


Anyone have any ideas? Im completely stumped. Is it a possibility that the PCM got damaged from the excess voltage going to it through the sensor wire? I would think that if it had, it wouldn't display anything on that particular pin, but who knows. I have a complete harness from a 2002 f150 4.6, but Im not sure if it would even work, and id really like to avoid having to replace it.


Sorry for talking your ears off. Any help would be greatly appreciated, because as a prior ford dealer tech, I refuse to let this thing beat me.


Thank You
Andy

 

A bit late to this party but what brand of 02 sensors were used here?

I've heard from time-to-time the off brands can cause PITA readings like yours.

I'm pretty sure you'd use good parts but its a valid question---I think?

 

Im using bosch.

 

I hope I don't have my facts/memories wrong here........

Seems there was or could be an issue with Bosch o2 sensors, that the ECM doesn't like them for whatever reason. Most who've previously deal with something similar have switched to Motorcraft brand which cleared up this issue.

Your voltage reading swings when moving the wire harness definitely say something is amiss there----that needs to be discovered and repaired first I'm guessing.

Sadly that's the extent of my knowledge and experience here---hope you find an easy and cheap solution.

 

The only reason i dont suspect that the sensor is causing the issue was that i was getting battery voltage on the o2 sensor signal wire with the sensor completely unplugged, so that was telling me that the voltage was getting onto that wire somewhere between the o2 sensor connector, and the pcm. I have heard that bosch sensors can cause issues, but the one on the front drivers side was switching back and forth just fine when i watched it on the scanner.

 

At this point hand following the sensor's connector and wire harness back to the PCM should be all that's left to check and double check?

Could the PCM be at fault here?

(Sorry I'm not well versed on the 02 sensor proper operation---you have a much better understanding of what is correct and when something is amiss too.)