4x4Countryboy

I have a 89 Ford f150 with the inline6.I have code 41(koeo) hego sensor voltage low/system lean,hego signal out of range/always lean. What could be the problem? But the thing I don't get is when I start the truck and run the code reader I get code 11 system ok. What is going on here??? I need help ASAP I have a 645mile trip to make in a couple of days. Some times the truck will sit there and crank and after a few trys the truck will start but sometimes the truck will start right up. But tonight I noticed sometimes at idle which is low the dome light and dash lights will flicker but only sometimes.

4x4Countryboy

So I replaced the o2 sensor and still geting the same code. But the truck is running better but still a rough idle. Any ideas???