Topic: Did something stupid

[95 Lowbuck]

So I got the bright idea to go thru all my wiring connectors
in the engine compartment, which means cleaning with
electronic cleaner and using dielectric grease at assembly.
Everything went fine untill I did the O2 sensor connector
on the exuast about a week later.
The check engine light now comes on after I drive it about 10 min.
and I get a #51 code. (lean air fuel ratio)
I've since had the connector upart, cleaned it, and looks in good shape.
Can you screw up this sensor just by disconnecting it?
Will this code reset itself after some time?

[VA_YJ]

There are several possible causes for Code 51:
1. Low Fuel Pressure - check on fuel rail fitting - should be 31 lbs. with vacuum on regulator
2. Vaccum leak - puts extra air in the mixture!  Did you knock any lines loose?
3. O2 Sensor failure - when oxygen content is low (rich mixture), the O2 sensor signal should be about 1 volt, when oxygen content is high, the signal should be about 0.1 volt.  You can measure the output voltage under different conditions (remove and plug vacuum line on regulator to increase pressure and induce rich condition).
4. You did something stupid - maybe the connectors are not making good contact from your disassembly/reassembly - check to make sure the female connectors have not "spread open" 

I don't think this problem will go away on it's own, but you can reset the PCM (computer) and give it a try.   Good luck!  

[95 Lowbuck]

Ended up being a combination of a bad O2 senser
and a bad vacuum port plug on the manifold.
Thank's for the input VA-YJ.
Also how do you clear the codes off the computer?

[BlueFlu]

You can clear them by disconnecting the battery for a few mins or pick up a OBD2 scan tool. 
I like using a scan tool myself so I don't have to reset my radio.  I know weak reason.
Some parts house will clear codes also.

[VA_YJ]

Glad you found the problem.  For clearing the codes, you can disconnect the battery as blueflu says, some folks touch the postive and negative cables together for a faster reset.  The scan tool removes the diagnostic trouble codes with totally resetting the computer.  If you have mods (e.g., mustang injectors, 4.0 TB), then your computer will loose any "learning" that has occurred and will take a while to optimize again.  As blueflu says, some auto parts places (e.g., Advance) will scan for you at no charge and you could ask them to reset.  I have my own ODB I, ODB II tool.  My '95 YJ is ODB I.