What does this mean!!!

hey I don't have an answer for you but I am getting the same thing. Are you blowing small amounts of black smoke from your exhaust?

The O2 sensor reads emission gases in the exhaust header and tells the computer to run rich or lean but over time from extreme heat etc. they become less effective causing a richer condition, the life cycle of the O2 sensor is usually 30k miles.

There are other fuel managers at cold start and normal operation that work in tandum like IAC, TPS and ECT that should be checked...go back and "pull codes" KOEO = key on engine off and see if there is anything related there....www.fordfuelinjection.com .....everything you need is all there.

If "voltage" is low from the sensor you'll need to either back probe the wiring and find out what it is and supposed to be OR replace the sensor with a Mototrcraft or Bosch, not expensive and all procedures are in the Haynes Manual or www.broncolinks.com....

Good Luck ~ :thumbup

I wouldn't worry about the wiring yet, unless a wire was cut, pulled, or pinched when the engine was changed. Seems to be a Jeep problem. :haha

Take the DTC at its face value. Why was the engine replaced? Did the old one blow a head gasket or burn coolant? If there were contaminants like that in the exhaust stream, chances are good that your oxygen sensor was poisoned. It's also fairly common to damage the sensor during removal and installation of the exhaust system and/or engine, so a good physical inspection is called for. Any faults found mean you need to replace it.

If the body looks clean, and the electrical connector is fully plugged in (may want to pull it apart and reconnect just to be sure it's clean), then I'd start looking at things like vacuum leaks, fuel pressure, etc.

i upgraded my exhaust to full 3" and got a new 02 sensor. that was about a year ago. the old engine was replaced because the main bearings went bad. oil everywhere. i'm going to check the wires and make sure that there arent any grounds. i did the KOEO and got 11 (all good). and when i did KOER i also got a 77 but that said operator error for not giving it throttle when it was testing.

was the engine warmed up before you did the tests? what temp tstat did you install in the motor? what is your timing set at and are you pulling the spout connector when doing so?

yes the engine was nice and hot. the code only pops up when ever it is hot. the timing is around 10 and i pulled the spout the first time when i set the timeing but not when i make little adjustments.

ok so i check everything over and all i found so far was that the wire that goes to the 02 senser got too close to the headers and look a little melted on the out side. could that cause a ground and/or the voltage to get messed up?

zippome said:

ok so i just put a new long block engine in and im at about 400 miles on it. but now im getting a check engine light and when i check it with the code reader i get a 41. which is "HEGO (HO2S) sensor voltage low / system lean" I have been having a hard time getting the timeing just right so i think thats what it is. i just can't think of what else it can be with EFI.

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I didnt read all the responses, but I would suggest checking the O2 sensor ground wire. It is orange, has a ring terminal end and bolts to the middle of the intake in the rear.

zippome said:

ok so i check everything over and all i found so far was that the wire that goes to the 02 senser got too close to the headers and look a little melted on the out side. could that cause a ground and/or the voltage to get messed up?

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Absolutely, and I'd be willing to be that more than a single wire's insulation was damaged. You need to re-route those wires, as far away as practical from the exhaust system, and inspect the rest of the wires along that part that was burned.

yes exactly what Sig said.


also anytime you make adjustments to the timing the spout must be pulled regardless how minor otherwise it wont really change

j. r. Nice said:

I didnt read all the responses, but I would suggest checking the O2 sensor ground wire. It is orange, has a ring terminal end and bolts to the middle of the intake in the rear.

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i dont see this wire. unless it is one of the three that go into the senser. but none of them connect to the middle of the intake.

zippome said:

i dont see this wire. unless it is one of the three that go into the senser. but none of them connect to the middle of the intake.

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No, it's not near the sensor. It sticks out of the loom of the wiring harness that traverses the back of the engine. You can find it by putting your hand around the loom and following it across the back of the engine.

You can also use a mirror. I had to lay on top of the core support to reach mine. Trust me it's there. It serves only as a PCM ground for the O2 sensor. It isnt hooked to the sensor, it comes out of the PCM.

x3 on fixing the burnt wires.

well that ground could be the problem becasue i can't find it. i followed the wire harness all the behind the engine and i don't see where it breaks off. i'll look again in the morning.

update time. i am sure that the timing is right now. and i replaced those burnt wires. the "check engine" light hasn't come on yet, but now it is doing something different. when ever it is cold and in idle the RPM's will go up and down and up and down and sometimes die. it was doing it before i fixed the wires and it got better, but it still does it. i was thinking EGR but i had a bad one before and just replaced it.

kemicalburns said:

yes exactly what Sig said.


also anytime you make adjustments to the timing the spout must be pulled regardless how minor otherwise it wont really change

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yes the timing will change, but you will not have any idea what the base timing is. the engine changes the advance only.

you really need to pull the spout to adjust timing. and put a new O2 in just because it is a new engine. Verify wiring is good.

ok so new problem kinda..... now when it is cold, it just hates to start. i have to spray the intake filter with brake cleaner then it will start but the it acts like it is flooded. then the rpm's will still go up and down and then die so i have to keep my foot on the gas a little bit. once it gets warmed up it runs like a dream, better than ever. but after a while i will get two codes. one for the O2 sensor and the other for the EGR valve. i just put a new EGR valve in there but all of the stuff sounds like the EGR.

on another note i also want to put a new computer in it becasue when i do the timing test it doesnt go forward 20 degrees only about 16-17, but i dont know where to start for that.

Try testing your ECT sensor, regarding the cold-start problems. Also test your fuel pressure.

As for the ignition timing not advancing, do you mean that it only advances to 16-17°, when you replace the SPOUT plug and observe the marks at warm idle? If so, that's completely normal. My own truck sits at 16° while warm idling, and only changes (by a degree or two) when it needs to make slight speed/torque adjustments.

what code numbers are you getting now?

I don't remember exactly what code numbers they were. One was the same as before 41. And the other was something new but it said that it was a problem with the EGR. And I got another that said that my idle is too high.