O2 sensor Wrong?

[holyford86]

Seen this several times in rangers and explorers, every single one had been welded on the exhaust without the computer being disconnected, every single one got rid of these codes after a computer replacement. One of them was a 97 explorer with a 5.0 we pulled our hair out for days trying to figure it out. Ended up pulling the engine down to block, doing all related gaskets, testing (and replacing) all o2 sensors, and even testing the wiring harness between the computer and sensors. Replaced the computer with a good used unit and the problem immediately went away and hasn't been back. Another one in an 04 ranger with a 4.0, same issues, was purchased at auction and all o2 sensors and top end gaskets done, had custom welded on dual exhaust with the same codes as the ex. I'm not about throwing parts at issues but this is becoming a pattern for me.

 

[Dads Toy]

Seen this several times in rangers and explorers, every single one had been welded on the exhaust without the computer being disconnected, every single one got rid of these codes after a computer replacement. One of them was a 97 explorer with a 5.0 we pulled our hair out for days trying to figure it out. Ended up pulling the engine down to block, doing all related gaskets, testing (and replacing) all o2 sensors, and even testing the wiring harness between the computer and sensors. Replaced the computer with a good used unit and the problem immediately went away and hasn't been back. Another one in an 04 ranger with a 4.0, same issues, was purchased at auction and all o2 sensors and top end gaskets done, had custom welded on dual exhaust with the same codes as the ex. I'm not about throwing parts at issues but this is becoming a pattern for me.

That's good stuff to know. Well the blown fuse to the O2 heater circuit seem to be a big issue. I have been driving it now for about a week since replacing the fuse. Cold morning starts are much better. Don't get the O2 heater code no more. Just the lean code. Be working on that issue this weekend.

 

[Dads Toy]

clean map sensor

I clean the MAP sensor today. Cleared the codes. So hope this works. Took it for a quick trip around the block. Seems to work ok. Will see how it works once I drive it more.

 

[AllanD]

The "Downstream sensor" generally referenced as a "Catalyst monitor"
is actually a narrow band O2 sensor as it is dealing with gasses post catalyst
which are at least theoretically cleaner...

Mostly it is different because it is designed to do a different job.

 

[Dads Toy]

Update

Will its been a couple of weeks now. Thought I would give a progress update. Might help someone some day. Truck is running good since replace the heater O2 fuse. Cold starts run fine. Still getting the too Lean bank code. I cleared it and work fine for about a day. Then it pop back up. I cleaned the MAF, intake tube etc. Thought that would have done it. Codes came back. So now I leaning on to the fuel system. Thinking replacing the fuel filter. Truck does run fine, has a little mis. Can't find any vacuum leaks.

 

[RonD]

After engine is warmed up, let it idle and unplug IAC Valve, this will cause it to close.
Idle should drop to around 500rpms or engine may even stall, either is fine, it means no vacuum leak.
If idle stays up then there is some air leaking in from somewhere, try testing for leaks at this time, when idle drops you found the leak.


Fuel pressure test might tell you something, if pressure is lower than computer expects then it has to open injectors longer, so will set a lean code because fuel trim is high.