Ok Don't understand why I'm not getting a response from anyone ,,, its 94 Ford F150 XL 4.9L /300 6 cylinder , If I'm missing something here from previous posts , PLEASE , let me know . Doing the best I can here with info on truck ,,, could someone explain to me what or how to understand the 173 code , HEGO , scanner definition Heated exhaust gas oxygen voltage indicates " rich " ( Bank 1 ) ,, I do not understand what that means , Does this have to do with rear tank pump ???? Or something else in system ,, Can I disconnect rear tank for temporary or is that going to cause more problems ?? Just need the HELP here ,,, I depend on this truck , and I do try to take care of it the best I can . It has just caught me off guard financially at a bad time , so I'm doing the best with what I have . koeo : 111 1 173 628 koer 1 412 173 538 ( 537 ) 536 632 ,, I may have miscounted on that 537 , I haven't find a definition for that one yet ,, But I'm hoping some of you will respond to give me a hand here ,,,,,,,,,, Aside from the E4OD issues ,,, it has ran really well up till recently this year,, Still bare in mind that I had to cut the rear tank hose and plug it , because of getting stuck out of town 3-4 yrs ago , it was only one , left the other hose's connected to tank and pump still connected . If this is part of the problem ,, please tell me ,,,, it is just with in the last month and a half that I noticed fumes coming from rear tank outlet , smell is pretty strong , What I don't understand is what is going on there, being the fuel line is plugged , is something getting by thru other hose ???? I need to have this tank temporarily shut down until I can afford to do it right down the road , Is this causing in any way a chain reaction of events in the system after all this time ???? Someone Please help here .

 

Not sure when your original post was, and your truck is 'way newer than my normal experience range - but I just copied your "heated exhaust gas etc" phrase into the search bar on Yahoo and got multiple pages of responses essentially saying that bank 1 is showing rich. Another search asking which says bank 1 on the 4.9L is the rear of the two manifolds, so your O2 sensor is telling you one or all of your cylinders 4,5,6 are running rich. Possible causes are shown in
https://www.2carpros.com/questions/f...indicates-lean which was the first hit in Yahoo search - not too hard to locate.

I suspect if you did a search (see "search" in the middle blue bar above) you would get lots of hits in the forums as well. Good luck.