I'm getting the code 41 for lean/O2 sensor and went through the check list from the manual and it saying to replace the 02 sensor after all the testing. It is a brand new sensor and one of the checks was to hook up a DC meter between it and the negative on the battery and measure the voltage. <0.45 V was a fail. Mine only got up to the high 0.3 range, but varied with the engine. The test called for "choking" the engine to create an artificial rich environment which I did at fast idle. When I installed this, I just took the old one out and put the new one in, should I have cleaned the contact area so it had a really good ground? It seems like the sensor is reacting to the O2 levels, but not putting out a high enough voltage. My other question is would a vacuum leak create a scenario like this? I was able to stall the truck by choking it, seems like it would have just sucked air though a leak. I ask the vacuum leak question because it is also running rough at all speeds. I'm going to to the carb cleaner check tonight.

 

Running rough at idle along with the lean error code would point to a vacuum leak somewhere.

 

0.3 is less than 0.45, how does that fail?

 

Sorry, it stated that it had to be greater than 0.45 or it should be replaced. I checked for vacuum leaks and it doesn't appear to have any, the carb cleaner trick would not change anything and I put a vac gauge on it and it held in the green about 18" Hg at idle so I'm thinking it's not a vacuum thing. My only wonder is if it needs to have a certain quality of ground and that might make it go higher.

 

Is your engine block grounded to the frame and body? I'm following your post because I'm having the same problem.

 

Oh, I dunno... do you have an ohm meter?

If you want to stop wondering, remove the device, put one probe in the hole and the other probe on the negative battery terminal and read the resistance (you shouldn't have any).

Quality of connections is certainly important but is more important at higher current draws, this thing uses a minuscule amount of power and therefore doesn't need a large contact area.

But if your system is rusted and corroded to the point that the sensor won't ground, then cleaning it should help.

Might also go Googleing on how to check if a sensor is good or not, I'd imagine there'd be a resistance test that could be performed on it....

 

Yes, just went and checked that. If I put the meter on the positive battery lead and touch the sensor or the manifold I get 12+V

I went through the alldatadiy Pinpoint test for Fuel control (code 41)and they say replace the sensor. It seems odd that two Bosch O2 sensors would both have the same issue and be reading low. The truck has a rough idle even when cold, and if I remember correctly, the computer ignores the 02 sensor for a couple of minutes till it is up to temp. That tells me something else is leaning it out. but it doesn't appear to be a vacuum leak. May be something with carb., but I rebuilt that a few months ago and it seemed to be operating flawlessly (this issues started with an ignition problem that I fixed)

 

I would guess you did something while fixing the ignition to cause this problem....... Can you un-do what you did and see if the problem goes away (even though the other problem will likely return)?

 

Have you tried richening the fuel mixture screw on the carb? If the carb is adjusted lean, it will idle and run rough, and throw a code 41.

Are these exact fit O2 sensors, or are they multiple fit where you have to add your own connector? How is the O2 connector on the truck side.

Test the wire for continuity and resistance between the computer connector and the O2 sensor connector truck side with both the computer and the O2 sensor unplugged from them.

If <0.45 V is a fail, do you have the correct O2 sensor for your application?

As CTUBUTIS states, recheck your ignition fixes. Check the wires etc...