I recently purchased a 1985 F-150 XLT Lariat (5.0 EFI - 2WD) with 145K miles on it and have been having issues with it running rough and stalling at low rpms. I ran the codes and came up with 41 in KOER mode (Heated Oxygen Sensor circuit indicates system lean, right side).

My first question is whether this code should come up when this truck does not have a heated O2 sensor. I found the one and only O2 sensor on the right (passenger) side in the exhaust manifold and eventually located the plug at the end of the pigtail. The O2 sensor has only one wire and the plug appears to be the single wire type (actually haven't seen it yet but was able to feel it by reaching from driver side up over bell housing and fondled it with two fingers).

I am thinking that this code will come up even though I don't have a heated O2 sensor because they didn't want to add three or more codes to the list. I ordered a new one and the Denso OE replacement is, in fact, a single wire unheated O2 sensor. Am I missing something here?

My second question is whether it makes sense to cut the wires on the new and old sensors and splice them rather than trying to disconnect and reinstall the new plug/connector that can only be reached (at this point) with the tips of my two longest fingers?

I am sure these questions have come up in the past but I haven't found the answers yet. Any assistance on this issue, or other tips on O2 sensors in general would be greatly appreciated. I am hoping the new sensor will resolve the 41 Code but if it doesn't, my next question will be how to narrow down the cause and the fix for the system lean, right side problem.

Thanks in advance.

Kent

 

From where did you find that definition to Code 41?

Second question: There are three sets of codes to be pulled; from which set does that 41 appear?

 

This definition comes from the Haynes manual.

Innova code reader manual defines this code as "HEGO (HO2S) sensor voltage low/system lean".

I should have mentioned, the Code was 41R acquired during the Key On Engine Running self test.

 

Code 41 is a oxygen sensor code. Some EECIV systems had heated oxygen sensors, some didn't.

 

To my knowledge, the heated O2 sensors didn't come about until after this era of trucks but that's just what's in my mind right now, based on no verifiable data whatsoever.

Regardless of it being heated or not, your computer says yours needs attention....

 

Thanks Dave. The new sensor arrives tomorrow and I don't want t go through the trouble of removing the old and installing the new if it's the wrong one.

 

When you do the replacement, apply anti-seize to the threads to make future removal easier.

 

Thank you all for the input. Any suggestions about reaching the connector vs. cutting and splicing the wires?

 

You can cut the wires, but any type of butt splice or connector you use may melt or not last, the wire is usually a high temp type of wire and the wire is usually pretty close to the exhaust where regular connectors can get damaged. You can probably do it, just think about how the heat is radiating from the exhaust.

 

That makes sense. Thanks.

The Denso model I picked up today has a braided thermal sleeve to protect the wire from the heat but it won't go over the butt connector. I plan on cutting the wires tomorrow morning unless I somehow figure out how to get more than two fingertips on the on the existing plug/connector before then.

Thanks again.

Kent

 

You can run a heated sensor if you like. All you have to do is add a power and ground for the heater part. Doing so will let your truck get to closed-loop operation sooner.

 

That never occurred to me but it makes perfect sense. Thanks.

I got caught up with the code discrepancy (Heated vs. Unheated) and locating the connector. At this point, I am thinking that the truck is running much smoother (after running one tank with fuel injector cleaner and checking vacuum hoses) so I was planning to just run the codes one more time before I install the unheated sensor today when I have the time.

I wonder how much benefit there would be to installing a heated sensor. I realize that running it rich in default mode for a minute or two for each startup means a little extra fuel consumption and carbon build up over the long run. Are there any other advantages to the heated sensors that I am missing?

Thanks again for all the help.

Kent

 

Technically it doesn't run "rich" without the oxygen sensor. What it does is run in open loop. This means the computer looks at various sensors like engine temp, map, and rpm info, and then looks up how much fuel it should provide by using tables of info the engineers loaded into the memory of the computer. If the engine is completely stock, these values are really close to what it needs and it runs very close to the proper ratio. They do have routines they program in to make it run a little rich on purpose, but usually this is just to warm up the catalytic converter quicker. But it's all planned.

Once the oxygen sensor gets warm enough, the computer goes into closed loop. The computer starts looking at the oxygen sensor for the air to fuel instead of the memory tables, and it tweaks the fuel according to the what the oxygen sensor tells it. You can have a "lazy" sensor and it can mess the air to fuel up some, but if your sensor is failed completely the computer will recognize this and after it looks at it for a period of time it gives up on it and goes back to using the tables (open loop) and will set the code 41.

Other situations can also cause a code 41. For example if your fuel regulator had a leak and was pouring a lot of fuel into the engine, the engine would continually run rich. When the engine warmed up and the computer starts looking at the oxygen sensor it would find the sensor all the way to the rich side, and trying to lean the engine doesn't help the situation, so in this case also it would throw a code 41, since it can't get the oxygen sensor to react correctly, even though it's not the sensor's fault.

 

Thanks again Dave. It sounds like there is not a major downside to running in open loop (whether it is long term with a bypassed sensor or short term waiting for the sensor to warm up) other than possibly failing inspection due to emissions. Of course, I want to have the O2 sensor functioning so I can be alerted to any irregularities, but I am not convinced a heated O2 sensor gives me a significant advantage over the unheated unit.

Many thanks for all the positive input.

Kent

 

I am happy to report that the old O2 sensor has finally been removed and the new one (unheated) has been installed without cutting any wires. Disconnecting a portion of the wheel well gave me better access for my tools and a good view of the connector hiding between the engine and the firewall. With the slack in the wire after removing the sensor, the connector could be repositioned and accessed with both hands by reaching around the intake manifold.

On top of that, the 41R code is now gone and the truck is running better than ever. If the Giants had won, it might have been a perfect day.

Anyway, thanks again for all your support. For my first thread, I was quite pleased with the knowledgeable input and suggestions. Muchos Thankiotos!

Kent